Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-22 Thread Michael Ellerman 
"Paul E. McKenney"  writes:
> On Fri, Apr 21, 2017 at 09:27:59AM +0200, Paolo Bonzini wrote:
>> On 21/04/2017 06:17, Paul E. McKenney wrote:
>> >> Thanks, this looks perfect to me, and if you're happy to put it on top
>> >> of your tree that would limit the breakage to a smaller history window,
>> >> so that would be ideal.
>> >>
>> >> Tested-by: Michael Ellerman 
>> > Thank you, Michael!
>> > 
>> > Paolo, does this look good to you?  My upstream maintainer will be much
>> > more likely to take this with your ack.  ;-)
>> 
>> Sure,
>> 
>> Acked-by: Paolo Bonzini 
>> 
>> since I don't expect conflicts between whoever applies this patch and
>> the KVM tree.
>
> Applied, thank you!

Thanks all.

cheers

Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-22 Thread Michael Ellerman 
"Paul E. McKenney"  writes:
> On Fri, Apr 21, 2017 at 09:27:59AM +0200, Paolo Bonzini wrote:
>> On 21/04/2017 06:17, Paul E. McKenney wrote:
>> >> Thanks, this looks perfect to me, and if you're happy to put it on top
>> >> of your tree that would limit the breakage to a smaller history window,
>> >> so that would be ideal.
>> >>
>> >> Tested-by: Michael Ellerman 
>> > Thank you, Michael!
>> > 
>> > Paolo, does this look good to you?  My upstream maintainer will be much
>> > more likely to take this with your ack.  ;-)
>> 
>> Sure,
>> 
>> Acked-by: Paolo Bonzini 
>> 
>> since I don't expect conflicts between whoever applies this patch and
>> the KVM tree.
>
> Applied, thank you!

Thanks all.

cheers

Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-21 Thread Paul E. McKenney 
On Fri, Apr 21, 2017 at 09:27:59AM +0200, Paolo Bonzini wrote:
> 
> 
> On 21/04/2017 06:17, Paul E. McKenney wrote:
> >> Thanks, this looks perfect to me, and if you're happy to put it on top
> >> of your tree that would limit the breakage to a smaller history window,
> >> so that would be ideal.
> >>
> >> Tested-by: Michael Ellerman 
> > Thank you, Michael!
> > 
> > Paolo, does this look good to you?  My upstream maintainer will be much
> > more likely to take this with your ack.  ;-)
> 
> Sure,
> 
> Acked-by: Paolo Bonzini 
> 
> since I don't expect conflicts between whoever applies this patch and
> the KVM tree.

Applied, thank you!

Thanx, Paul

Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-21 Thread Paul E. McKenney 
On Fri, Apr 21, 2017 at 09:27:59AM +0200, Paolo Bonzini wrote:
> 
> 
> On 21/04/2017 06:17, Paul E. McKenney wrote:
> >> Thanks, this looks perfect to me, and if you're happy to put it on top
> >> of your tree that would limit the breakage to a smaller history window,
> >> so that would be ideal.
> >>
> >> Tested-by: Michael Ellerman 
> > Thank you, Michael!
> > 
> > Paolo, does this look good to you?  My upstream maintainer will be much
> > more likely to take this with your ack.  ;-)
> 
> Sure,
> 
> Acked-by: Paolo Bonzini 
> 
> since I don't expect conflicts between whoever applies this patch and
> the KVM tree.

Applied, thank you!

Thanx, Paul

Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-21 Thread Paolo Bonzini 


On 21/04/2017 06:17, Paul E. McKenney wrote:
>> Thanks, this looks perfect to me, and if you're happy to put it on top
>> of your tree that would limit the breakage to a smaller history window,
>> so that would be ideal.
>>
>> Tested-by: Michael Ellerman 
> Thank you, Michael!
> 
> Paolo, does this look good to you?  My upstream maintainer will be much
> more likely to take this with your ack.  ;-)

Sure,

Acked-by: Paolo Bonzini 

since I don't expect conflicts between whoever applies this patch and
the KVM tree.

Paolo

Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-21 Thread Paolo Bonzini 


On 21/04/2017 06:17, Paul E. McKenney wrote:
>> Thanks, this looks perfect to me, and if you're happy to put it on top
>> of your tree that would limit the breakage to a smaller history window,
>> so that would be ideal.
>>
>> Tested-by: Michael Ellerman 
> Thank you, Michael!
> 
> Paolo, does this look good to you?  My upstream maintainer will be much
> more likely to take this with your ack.  ;-)

Sure,

Acked-by: Paolo Bonzini 

since I don't expect conflicts between whoever applies this patch and
the KVM tree.

Paolo

Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-20 Thread Paul E. McKenney 
On Fri, Apr 21, 2017 at 11:42:01AM +1000, Michael Ellerman wrote:
> "Paul E. McKenney"  writes:
> > On Thu, Apr 20, 2017 at 05:28:32PM +0200, Paolo Bonzini wrote:
> >> On 20/04/2017 05:40, Michael Ellerman wrote:
> >> > "Paul E. McKenney"  writes:
> >> > 
> >> > This change seems to have had the non-obvious effect of breaking the
> >> > powerpc KVM build.
> ...
> >> 
> >> Michael, if you want to move the two srcu structs at the end of struct
> >> kvm, that would be fine by me.  Please send a patch yourself so you can
> >> test it on PPC.  Thanks,
> >
> > On the off-chance that it is at all helpful, I have added the commit
> > shown below to -rcu.
> 
> As shown below :)
> 
> > If it helps, I am happy to push this, but am just as happy to drop it
> > in favor of some other fix. If at all possible, I would like to get
> > this into the upcoming merge window.
> 
> Thanks, this looks perfect to me, and if you're happy to put it on top
> of your tree that would limit the breakage to a smaller history window,
> so that would be ideal.
> 
> Tested-by: Michael Ellerman 

Thank you, Michael!

Paolo, does this look good to you?  My upstream maintainer will be much
more likely to take this with your ack.  ;-)

Thanx, Paul

> cheers
> 
> 
> >From a19a6617e2817e485ccc2f7cc5a97bd7ff769b87 Mon Sep 17 00:00:00 2001
> From: "Paul E. McKenney" 
> Date: Thu, 20 Apr 2017 17:30:06 -0700
> Subject: kvm: Move srcu_struct fields to end of struct kvm
> 
> Parallelizing SRCU callback handling increased the size of srcu_struct,
> which moved the kvm_arch field within the kvm struct out of reach of
> powerpc's current assembly code, resulting in the following sort of
> build error:
> 
> arch/powerpc/kvm/book3s_hv_rmhandlers.S:617: Error: operand out of range 
> (0xb328 is not between 0x8000 and 0x7fff)
> 
> This commit moves the srcu_struct fields in the kvm structure to follow
> the kvm_arch field, which again allows powerpc's assembly code to
> reach it.
> 
> Reported-by: Stephen Rothwell 
> Reported-by: Michael Ellerman 
> Reported-by: kbuild test robot 
> Suggested-by: Paolo Bonzini 
> Signed-off-by: Paul E. McKenney 
> ---
>  include/linux/kvm_host.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 2c14ad9..96c8e29 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -375,8 +375,6 @@ struct kvm {
>   struct mutex slots_lock;
>   struct mm_struct *mm; /* userspace tied to this vm */
>   struct kvm_memslots *memslots[KVM_ADDRESS_SPACE_NUM];
> - struct srcu_struct srcu;
> - struct srcu_struct irq_srcu;
>   struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
> 
>   /*
> @@ -429,6 +427,8 @@ struct kvm {
>   struct list_head devices;
>   struct dentry *debugfs_dentry;
>   struct kvm_stat_data **debugfs_stat_data;
> + struct srcu_struct srcu;
> + struct srcu_struct irq_srcu;
>  };
> 
>  #define kvm_err(fmt, ...) \
> -- 
> cgit v1.1

Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-20 Thread Paul E. McKenney 
On Fri, Apr 21, 2017 at 11:42:01AM +1000, Michael Ellerman wrote:
> "Paul E. McKenney"  writes:
> > On Thu, Apr 20, 2017 at 05:28:32PM +0200, Paolo Bonzini wrote:
> >> On 20/04/2017 05:40, Michael Ellerman wrote:
> >> > "Paul E. McKenney"  writes:
> >> > 
> >> > This change seems to have had the non-obvious effect of breaking the
> >> > powerpc KVM build.
> ...
> >> 
> >> Michael, if you want to move the two srcu structs at the end of struct
> >> kvm, that would be fine by me.  Please send a patch yourself so you can
> >> test it on PPC.  Thanks,
> >
> > On the off-chance that it is at all helpful, I have added the commit
> > shown below to -rcu.
> 
> As shown below :)
> 
> > If it helps, I am happy to push this, but am just as happy to drop it
> > in favor of some other fix. If at all possible, I would like to get
> > this into the upcoming merge window.
> 
> Thanks, this looks perfect to me, and if you're happy to put it on top
> of your tree that would limit the breakage to a smaller history window,
> so that would be ideal.
> 
> Tested-by: Michael Ellerman 

Thank you, Michael!

Paolo, does this look good to you?  My upstream maintainer will be much
more likely to take this with your ack.  ;-)

Thanx, Paul

> cheers
> 
> 
> >From a19a6617e2817e485ccc2f7cc5a97bd7ff769b87 Mon Sep 17 00:00:00 2001
> From: "Paul E. McKenney" 
> Date: Thu, 20 Apr 2017 17:30:06 -0700
> Subject: kvm: Move srcu_struct fields to end of struct kvm
> 
> Parallelizing SRCU callback handling increased the size of srcu_struct,
> which moved the kvm_arch field within the kvm struct out of reach of
> powerpc's current assembly code, resulting in the following sort of
> build error:
> 
> arch/powerpc/kvm/book3s_hv_rmhandlers.S:617: Error: operand out of range 
> (0xb328 is not between 0x8000 and 0x7fff)
> 
> This commit moves the srcu_struct fields in the kvm structure to follow
> the kvm_arch field, which again allows powerpc's assembly code to
> reach it.
> 
> Reported-by: Stephen Rothwell 
> Reported-by: Michael Ellerman 
> Reported-by: kbuild test robot 
> Suggested-by: Paolo Bonzini 
> Signed-off-by: Paul E. McKenney 
> ---
>  include/linux/kvm_host.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 2c14ad9..96c8e29 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -375,8 +375,6 @@ struct kvm {
>   struct mutex slots_lock;
>   struct mm_struct *mm; /* userspace tied to this vm */
>   struct kvm_memslots *memslots[KVM_ADDRESS_SPACE_NUM];
> - struct srcu_struct srcu;
> - struct srcu_struct irq_srcu;
>   struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
> 
>   /*
> @@ -429,6 +427,8 @@ struct kvm {
>   struct list_head devices;
>   struct dentry *debugfs_dentry;
>   struct kvm_stat_data **debugfs_stat_data;
> + struct srcu_struct srcu;
> + struct srcu_struct irq_srcu;
>  };
> 
>  #define kvm_err(fmt, ...) \
> -- 
> cgit v1.1

Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-20 Thread Michael Ellerman 
Paolo Bonzini  writes:
> Michael, if you want to move the two srcu structs at the end of struct
> kvm, that would be fine by me.  Please send a patch yourself so you can
> test it on PPC.  Thanks,

Paul beat me to it :)

I've confirmed it fixes the build break and the resulting kernel can
boot a KVM guest happily.

cheers

Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-20 Thread Michael Ellerman 
Paolo Bonzini  writes:
> Michael, if you want to move the two srcu structs at the end of struct
> kvm, that would be fine by me.  Please send a patch yourself so you can
> test it on PPC.  Thanks,

Paul beat me to it :)

I've confirmed it fixes the build break and the resulting kernel can
boot a KVM guest happily.

cheers

Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-20 Thread Michael Ellerman 
"Paul E. McKenney"  writes:
> On Thu, Apr 20, 2017 at 05:28:32PM +0200, Paolo Bonzini wrote:
>> On 20/04/2017 05:40, Michael Ellerman wrote:
>> > "Paul E. McKenney"  writes:
>> > 
>> > This change seems to have had the non-obvious effect of breaking the
>> > powerpc KVM build.
...
>> 
>> Michael, if you want to move the two srcu structs at the end of struct
>> kvm, that would be fine by me.  Please send a patch yourself so you can
>> test it on PPC.  Thanks,
>
> On the off-chance that it is at all helpful, I have added the commit
> shown below to -rcu.

As shown below :)

> If it helps, I am happy to push this, but am just as happy to drop it
> in favor of some other fix. If at all possible, I would like to get
> this into the upcoming merge window.

Thanks, this looks perfect to me, and if you're happy to put it on top
of your tree that would limit the breakage to a smaller history window,
so that would be ideal.

Tested-by: Michael Ellerman 

cheers


>From a19a6617e2817e485ccc2f7cc5a97bd7ff769b87 Mon Sep 17 00:00:00 2001
From: "Paul E. McKenney" 
Date: Thu, 20 Apr 2017 17:30:06 -0700
Subject: kvm: Move srcu_struct fields to end of struct kvm

Parallelizing SRCU callback handling increased the size of srcu_struct,
which moved the kvm_arch field within the kvm struct out of reach of
powerpc's current assembly code, resulting in the following sort of
build error:

arch/powerpc/kvm/book3s_hv_rmhandlers.S:617: Error: operand out of range 
(0xb328 is not between 0x8000 and 0x7fff)

This commit moves the srcu_struct fields in the kvm structure to follow
the kvm_arch field, which again allows powerpc's assembly code to
reach it.

Reported-by: Stephen Rothwell 
Reported-by: Michael Ellerman 
Reported-by: kbuild test robot 
Suggested-by: Paolo Bonzini 
Signed-off-by: Paul E. McKenney 
---
 include/linux/kvm_host.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 2c14ad9..96c8e29 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -375,8 +375,6 @@ struct kvm {
struct mutex slots_lock;
struct mm_struct *mm; /* userspace tied to this vm */
struct kvm_memslots *memslots[KVM_ADDRESS_SPACE_NUM];
-   struct srcu_struct srcu;
-   struct srcu_struct irq_srcu;
struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
 
/*
@@ -429,6 +427,8 @@ struct kvm {
struct list_head devices;
struct dentry *debugfs_dentry;
struct kvm_stat_data **debugfs_stat_data;
+   struct srcu_struct srcu;
+   struct srcu_struct irq_srcu;
 };
 
 #define kvm_err(fmt, ...) \
-- 
cgit v1.1

Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-20 Thread Michael Ellerman 
"Paul E. McKenney"  writes:
> On Thu, Apr 20, 2017 at 05:28:32PM +0200, Paolo Bonzini wrote:
>> On 20/04/2017 05:40, Michael Ellerman wrote:
>> > "Paul E. McKenney"  writes:
>> > 
>> > This change seems to have had the non-obvious effect of breaking the
>> > powerpc KVM build.
...
>> 
>> Michael, if you want to move the two srcu structs at the end of struct
>> kvm, that would be fine by me.  Please send a patch yourself so you can
>> test it on PPC.  Thanks,
>
> On the off-chance that it is at all helpful, I have added the commit
> shown below to -rcu.

As shown below :)

> If it helps, I am happy to push this, but am just as happy to drop it
> in favor of some other fix. If at all possible, I would like to get
> this into the upcoming merge window.

Thanks, this looks perfect to me, and if you're happy to put it on top
of your tree that would limit the breakage to a smaller history window,
so that would be ideal.

Tested-by: Michael Ellerman 

cheers


>From a19a6617e2817e485ccc2f7cc5a97bd7ff769b87 Mon Sep 17 00:00:00 2001
From: "Paul E. McKenney" 
Date: Thu, 20 Apr 2017 17:30:06 -0700
Subject: kvm: Move srcu_struct fields to end of struct kvm

Parallelizing SRCU callback handling increased the size of srcu_struct,
which moved the kvm_arch field within the kvm struct out of reach of
powerpc's current assembly code, resulting in the following sort of
build error:

arch/powerpc/kvm/book3s_hv_rmhandlers.S:617: Error: operand out of range 
(0xb328 is not between 0x8000 and 0x7fff)

This commit moves the srcu_struct fields in the kvm structure to follow
the kvm_arch field, which again allows powerpc's assembly code to
reach it.

Reported-by: Stephen Rothwell 
Reported-by: Michael Ellerman 
Reported-by: kbuild test robot 
Suggested-by: Paolo Bonzini 
Signed-off-by: Paul E. McKenney 
---
 include/linux/kvm_host.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 2c14ad9..96c8e29 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -375,8 +375,6 @@ struct kvm {
struct mutex slots_lock;
struct mm_struct *mm; /* userspace tied to this vm */
struct kvm_memslots *memslots[KVM_ADDRESS_SPACE_NUM];
-   struct srcu_struct srcu;
-   struct srcu_struct irq_srcu;
struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
 
/*
@@ -429,6 +427,8 @@ struct kvm {
struct list_head devices;
struct dentry *debugfs_dentry;
struct kvm_stat_data **debugfs_stat_data;
+   struct srcu_struct srcu;
+   struct srcu_struct irq_srcu;
 };
 
 #define kvm_err(fmt, ...) \
-- 
cgit v1.1

Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-20 Thread Paul E. McKenney 
On Thu, Apr 20, 2017 at 05:28:32PM +0200, Paolo Bonzini wrote:
> 
> 
> On 20/04/2017 05:40, Michael Ellerman wrote:
> > "Paul E. McKenney"  writes:
> > 
> >> diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
> >> index f2b3bd6c6bc2..0400e211aa44 100644
> >> --- a/include/linux/srcutree.h
> >> +++ b/include/linux/srcutree.h
> >> @@ -24,25 +24,75 @@
> > ...
> >> +/*
> >> + * Per-SRCU-domain structure, similar in function to rcu_state.
> >> + */
> >>  struct srcu_struct {
> >> -  unsigned long completed;
> >> -  unsigned long srcu_gp_seq;
> >> -  atomic_t srcu_exp_cnt;
> >> -  struct srcu_array __percpu *per_cpu_ref;
> >> -  spinlock_t queue_lock; /* protect ->srcu_cblist */
> >> -  struct rcu_segcblist srcu_cblist;
> >> +  struct srcu_node node[NUM_RCU_NODES];   /* Combining tree. */
> >> +  struct srcu_node *level[RCU_NUM_LVLS + 1];
> >> +  /* First node at each level. */
> >> +  struct mutex srcu_cb_mutex; /* Serialize CB preparation. */
> >> +  spinlock_t gp_lock; /* protect ->srcu_cblist */
> >> +  struct mutex srcu_gp_mutex; /* Serialize GP work. */
> >> +  unsigned int srcu_idx;  /* Current rdr array element. */
> >> +  unsigned long srcu_gp_seq;  /* Grace-period seq #. */
> >> +  unsigned long srcu_gp_seq_needed;   /* Latest gp_seq needed. */
> >> +  atomic_t srcu_exp_cnt;  /* # ongoing expedited GPs. */
> >> +  struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */
> >> +  unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */
> >> +  struct mutex srcu_barrier_mutex;/* Serialize barrier ops. */
> >> +  struct completion srcu_barrier_completion;
> >> +  /* Awaken barrier rq at end. */
> >> +  atomic_t srcu_barrier_cpu_cnt;  /* # CPUs not yet posting a */
> >> +  /*  callback for the barrier */
> >> +  /*  operation. */
> > 
> > This change seems to have had the non-obvious effect of breaking the
> > powerpc KVM build.
> > 
> > Because struct kvm contains two srcu_structs which are located
> > before the kvm_arch struct, the increase in size of srcu_struct has
> > caused the offset from the start of struct kvm to kvm_arch to be too big
> > for some of our asm.
> > 
> > struct kvm {
> > spinlock_t mmu_lock;
> > struct mutex slots_lock;
> > struct mm_struct *mm; /* userspace tied to this vm */
> > struct kvm_memslots *memslots[KVM_ADDRESS_SPACE_NUM];
> > struct srcu_struct srcu;
> > struct srcu_struct irq_srcu;
> > ...
> > struct kvm_arch arch;
> > 
> > 
> > Example error:
> >   arch/powerpc/kvm/book3s_hv_rmhandlers.S:617: Error: operand out of range 
> > (0xb328 is not between 0x8000 and 
> > 0x7fff)
> > 
> > Where line 617 is:
> >   lwz   r7,KVM_LPID(r9)
> > 
> > And the KVM_LPID constant comes from asm-offsets.s. The diff of old vs
> > new is:
> > 
> >   -->KVM_LPID 17752 offsetof(struct kvm, arch.lpid)  #
> >   +->KVM_LPID 45864 offsetof(struct kvm, arch.lpid)  #
> > 
> > 
> > We can probably just fix it by changing the asm to keep the address of
> > kvm_arch in a register, and then offset from that.
> 
> Michael, if you want to move the two srcu structs at the end of struct
> kvm, that would be fine by me.  Please send a patch yourself so you can
> test it on PPC.  Thanks,

On the off-chance that it is at all helpful, I have added the commit
shown below to -rcu.  If it helps, I am happy to push this, but am
just as happy to drop it in favor of some other fix.  If at all possible,
I would like to get this into the upcoming merge window.

Thanx, Paul

Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-20 Thread Paul E. McKenney 
On Thu, Apr 20, 2017 at 05:28:32PM +0200, Paolo Bonzini wrote:
> 
> 
> On 20/04/2017 05:40, Michael Ellerman wrote:
> > "Paul E. McKenney"  writes:
> > 
> >> diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
> >> index f2b3bd6c6bc2..0400e211aa44 100644
> >> --- a/include/linux/srcutree.h
> >> +++ b/include/linux/srcutree.h
> >> @@ -24,25 +24,75 @@
> > ...
> >> +/*
> >> + * Per-SRCU-domain structure, similar in function to rcu_state.
> >> + */
> >>  struct srcu_struct {
> >> -  unsigned long completed;
> >> -  unsigned long srcu_gp_seq;
> >> -  atomic_t srcu_exp_cnt;
> >> -  struct srcu_array __percpu *per_cpu_ref;
> >> -  spinlock_t queue_lock; /* protect ->srcu_cblist */
> >> -  struct rcu_segcblist srcu_cblist;
> >> +  struct srcu_node node[NUM_RCU_NODES];   /* Combining tree. */
> >> +  struct srcu_node *level[RCU_NUM_LVLS + 1];
> >> +  /* First node at each level. */
> >> +  struct mutex srcu_cb_mutex; /* Serialize CB preparation. */
> >> +  spinlock_t gp_lock; /* protect ->srcu_cblist */
> >> +  struct mutex srcu_gp_mutex; /* Serialize GP work. */
> >> +  unsigned int srcu_idx;  /* Current rdr array element. */
> >> +  unsigned long srcu_gp_seq;  /* Grace-period seq #. */
> >> +  unsigned long srcu_gp_seq_needed;   /* Latest gp_seq needed. */
> >> +  atomic_t srcu_exp_cnt;  /* # ongoing expedited GPs. */
> >> +  struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */
> >> +  unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */
> >> +  struct mutex srcu_barrier_mutex;/* Serialize barrier ops. */
> >> +  struct completion srcu_barrier_completion;
> >> +  /* Awaken barrier rq at end. */
> >> +  atomic_t srcu_barrier_cpu_cnt;  /* # CPUs not yet posting a */
> >> +  /*  callback for the barrier */
> >> +  /*  operation. */
> > 
> > This change seems to have had the non-obvious effect of breaking the
> > powerpc KVM build.
> > 
> > Because struct kvm contains two srcu_structs which are located
> > before the kvm_arch struct, the increase in size of srcu_struct has
> > caused the offset from the start of struct kvm to kvm_arch to be too big
> > for some of our asm.
> > 
> > struct kvm {
> > spinlock_t mmu_lock;
> > struct mutex slots_lock;
> > struct mm_struct *mm; /* userspace tied to this vm */
> > struct kvm_memslots *memslots[KVM_ADDRESS_SPACE_NUM];
> > struct srcu_struct srcu;
> > struct srcu_struct irq_srcu;
> > ...
> > struct kvm_arch arch;
> > 
> > 
> > Example error:
> >   arch/powerpc/kvm/book3s_hv_rmhandlers.S:617: Error: operand out of range 
> > (0xb328 is not between 0x8000 and 
> > 0x7fff)
> > 
> > Where line 617 is:
> >   lwz   r7,KVM_LPID(r9)
> > 
> > And the KVM_LPID constant comes from asm-offsets.s. The diff of old vs
> > new is:
> > 
> >   -->KVM_LPID 17752 offsetof(struct kvm, arch.lpid)  #
> >   +->KVM_LPID 45864 offsetof(struct kvm, arch.lpid)  #
> > 
> > 
> > We can probably just fix it by changing the asm to keep the address of
> > kvm_arch in a register, and then offset from that.
> 
> Michael, if you want to move the two srcu structs at the end of struct
> kvm, that would be fine by me.  Please send a patch yourself so you can
> test it on PPC.  Thanks,

On the off-chance that it is at all helpful, I have added the commit
shown below to -rcu.  If it helps, I am happy to push this, but am
just as happy to drop it in favor of some other fix.  If at all possible,
I would like to get this into the upcoming merge window.

Thanx, Paul

Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-20 Thread Paolo Bonzini 


On 20/04/2017 05:40, Michael Ellerman wrote:
> "Paul E. McKenney"  writes:
> 
>> diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
>> index f2b3bd6c6bc2..0400e211aa44 100644
>> --- a/include/linux/srcutree.h
>> +++ b/include/linux/srcutree.h
>> @@ -24,25 +24,75 @@
> ...
>> +/*
>> + * Per-SRCU-domain structure, similar in function to rcu_state.
>> + */
>>  struct srcu_struct {
>> -unsigned long completed;
>> -unsigned long srcu_gp_seq;
>> -atomic_t srcu_exp_cnt;
>> -struct srcu_array __percpu *per_cpu_ref;
>> -spinlock_t queue_lock; /* protect ->srcu_cblist */
>> -struct rcu_segcblist srcu_cblist;
>> +struct srcu_node node[NUM_RCU_NODES];   /* Combining tree. */
>> +struct srcu_node *level[RCU_NUM_LVLS + 1];
>> +/* First node at each level. */
>> +struct mutex srcu_cb_mutex; /* Serialize CB preparation. */
>> +spinlock_t gp_lock; /* protect ->srcu_cblist */
>> +struct mutex srcu_gp_mutex; /* Serialize GP work. */
>> +unsigned int srcu_idx;  /* Current rdr array element. */
>> +unsigned long srcu_gp_seq;  /* Grace-period seq #. */
>> +unsigned long srcu_gp_seq_needed;   /* Latest gp_seq needed. */
>> +atomic_t srcu_exp_cnt;  /* # ongoing expedited GPs. */
>> +struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */
>> +unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */
>> +struct mutex srcu_barrier_mutex;/* Serialize barrier ops. */
>> +struct completion srcu_barrier_completion;
>> +/* Awaken barrier rq at end. */
>> +atomic_t srcu_barrier_cpu_cnt;  /* # CPUs not yet posting a */
>> +/*  callback for the barrier */
>> +/*  operation. */
> 
> This change seems to have had the non-obvious effect of breaking the
> powerpc KVM build.
> 
> Because struct kvm contains two srcu_structs which are located
> before the kvm_arch struct, the increase in size of srcu_struct has
> caused the offset from the start of struct kvm to kvm_arch to be too big
> for some of our asm.
> 
> struct kvm {
>   spinlock_t mmu_lock;
>   struct mutex slots_lock;
>   struct mm_struct *mm; /* userspace tied to this vm */
>   struct kvm_memslots *memslots[KVM_ADDRESS_SPACE_NUM];
>   struct srcu_struct srcu;
>   struct srcu_struct irq_srcu;
> ...
>   struct kvm_arch arch;
> 
> 
> Example error:
>   arch/powerpc/kvm/book3s_hv_rmhandlers.S:617: Error: operand out of range 
> (0xb328 is not between 0x8000 and 0x7fff)
> 
> Where line 617 is:
>   lwz r7,KVM_LPID(r9)
> 
> And the KVM_LPID constant comes from asm-offsets.s. The diff of old vs
> new is:
> 
>   -->KVM_LPID 17752 offsetof(struct kvm, arch.lpid)#
>   +->KVM_LPID 45864 offsetof(struct kvm, arch.lpid)#
> 
> 
> We can probably just fix it by changing the asm to keep the address of
> kvm_arch in a register, and then offset from that.

Michael, if you want to move the two srcu structs at the end of struct
kvm, that would be fine by me.  Please send a patch yourself so you can
test it on PPC.  Thanks,

Paolo

Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-20 Thread Paolo Bonzini 


On 20/04/2017 05:40, Michael Ellerman wrote:
> "Paul E. McKenney"  writes:
> 
>> diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
>> index f2b3bd6c6bc2..0400e211aa44 100644
>> --- a/include/linux/srcutree.h
>> +++ b/include/linux/srcutree.h
>> @@ -24,25 +24,75 @@
> ...
>> +/*
>> + * Per-SRCU-domain structure, similar in function to rcu_state.
>> + */
>>  struct srcu_struct {
>> -unsigned long completed;
>> -unsigned long srcu_gp_seq;
>> -atomic_t srcu_exp_cnt;
>> -struct srcu_array __percpu *per_cpu_ref;
>> -spinlock_t queue_lock; /* protect ->srcu_cblist */
>> -struct rcu_segcblist srcu_cblist;
>> +struct srcu_node node[NUM_RCU_NODES];   /* Combining tree. */
>> +struct srcu_node *level[RCU_NUM_LVLS + 1];
>> +/* First node at each level. */
>> +struct mutex srcu_cb_mutex; /* Serialize CB preparation. */
>> +spinlock_t gp_lock; /* protect ->srcu_cblist */
>> +struct mutex srcu_gp_mutex; /* Serialize GP work. */
>> +unsigned int srcu_idx;  /* Current rdr array element. */
>> +unsigned long srcu_gp_seq;  /* Grace-period seq #. */
>> +unsigned long srcu_gp_seq_needed;   /* Latest gp_seq needed. */
>> +atomic_t srcu_exp_cnt;  /* # ongoing expedited GPs. */
>> +struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */
>> +unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */
>> +struct mutex srcu_barrier_mutex;/* Serialize barrier ops. */
>> +struct completion srcu_barrier_completion;
>> +/* Awaken barrier rq at end. */
>> +atomic_t srcu_barrier_cpu_cnt;  /* # CPUs not yet posting a */
>> +/*  callback for the barrier */
>> +/*  operation. */
> 
> This change seems to have had the non-obvious effect of breaking the
> powerpc KVM build.
> 
> Because struct kvm contains two srcu_structs which are located
> before the kvm_arch struct, the increase in size of srcu_struct has
> caused the offset from the start of struct kvm to kvm_arch to be too big
> for some of our asm.
> 
> struct kvm {
>   spinlock_t mmu_lock;
>   struct mutex slots_lock;
>   struct mm_struct *mm; /* userspace tied to this vm */
>   struct kvm_memslots *memslots[KVM_ADDRESS_SPACE_NUM];
>   struct srcu_struct srcu;
>   struct srcu_struct irq_srcu;
> ...
>   struct kvm_arch arch;
> 
> 
> Example error:
>   arch/powerpc/kvm/book3s_hv_rmhandlers.S:617: Error: operand out of range 
> (0xb328 is not between 0x8000 and 0x7fff)
> 
> Where line 617 is:
>   lwz r7,KVM_LPID(r9)
> 
> And the KVM_LPID constant comes from asm-offsets.s. The diff of old vs
> new is:
> 
>   -->KVM_LPID 17752 offsetof(struct kvm, arch.lpid)#
>   +->KVM_LPID 45864 offsetof(struct kvm, arch.lpid)#
> 
> 
> We can probably just fix it by changing the asm to keep the address of
> kvm_arch in a register, and then offset from that.

Michael, if you want to move the two srcu structs at the end of struct
kvm, that would be fine by me.  Please send a patch yourself so you can
test it on PPC.  Thanks,

Paolo

Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-20 Thread Paul E. McKenney 
On Thu, Apr 20, 2017 at 01:40:13PM +1000, Michael Ellerman wrote:
> "Paul E. McKenney"  writes:
> 
> > diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
> > index f2b3bd6c6bc2..0400e211aa44 100644
> > --- a/include/linux/srcutree.h
> > +++ b/include/linux/srcutree.h
> > @@ -24,25 +24,75 @@
> ...
> > +/*
> > + * Per-SRCU-domain structure, similar in function to rcu_state.
> > + */
> >  struct srcu_struct {
> > -   unsigned long completed;
> > -   unsigned long srcu_gp_seq;
> > -   atomic_t srcu_exp_cnt;
> > -   struct srcu_array __percpu *per_cpu_ref;
> > -   spinlock_t queue_lock; /* protect ->srcu_cblist */
> > -   struct rcu_segcblist srcu_cblist;
> > +   struct srcu_node node[NUM_RCU_NODES];   /* Combining tree. */
> > +   struct srcu_node *level[RCU_NUM_LVLS + 1];
> > +   /* First node at each level. */
> > +   struct mutex srcu_cb_mutex; /* Serialize CB preparation. */
> > +   spinlock_t gp_lock; /* protect ->srcu_cblist */
> > +   struct mutex srcu_gp_mutex; /* Serialize GP work. */
> > +   unsigned int srcu_idx;  /* Current rdr array element. */
> > +   unsigned long srcu_gp_seq;  /* Grace-period seq #. */
> > +   unsigned long srcu_gp_seq_needed;   /* Latest gp_seq needed. */
> > +   atomic_t srcu_exp_cnt;  /* # ongoing expedited GPs. */
> > +   struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */
> > +   unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */
> > +   struct mutex srcu_barrier_mutex;/* Serialize barrier ops. */
> > +   struct completion srcu_barrier_completion;
> > +   /* Awaken barrier rq at end. */
> > +   atomic_t srcu_barrier_cpu_cnt;  /* # CPUs not yet posting a */
> > +   /*  callback for the barrier */
> > +   /*  operation. */
> 
> This change seems to have had the non-obvious effect of breaking the
> powerpc KVM build.
> 
> Because struct kvm contains two srcu_structs which are located
> before the kvm_arch struct, the increase in size of srcu_struct has
> caused the offset from the start of struct kvm to kvm_arch to be too big
> for some of our asm.
> 
> struct kvm {
>   spinlock_t mmu_lock;
>   struct mutex slots_lock;
>   struct mm_struct *mm; /* userspace tied to this vm */
>   struct kvm_memslots *memslots[KVM_ADDRESS_SPACE_NUM];
>   struct srcu_struct srcu;
>   struct srcu_struct irq_srcu;
> ...
>   struct kvm_arch arch;
> 
> 
> Example error:
>   arch/powerpc/kvm/book3s_hv_rmhandlers.S:617: Error: operand out of range 
> (0xb328 is not between 0x8000 and 0x7fff)
> 
> Where line 617 is:
>   lwz r7,KVM_LPID(r9)
> 
> And the KVM_LPID constant comes from asm-offsets.s. The diff of old vs
> new is:
> 
>   -->KVM_LPID 17752 offsetof(struct kvm, arch.lpid)#
>   +->KVM_LPID 45864 offsetof(struct kvm, arch.lpid)#
> 
> 
> We can probably just fix it by changing the asm to keep the address of
> kvm_arch in a register, and then offset from that.

Ouch!

What do you need from me?

Thanx, Paul

Re: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-20 Thread Paul E. McKenney 
On Thu, Apr 20, 2017 at 01:40:13PM +1000, Michael Ellerman wrote:
> "Paul E. McKenney"  writes:
> 
> > diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
> > index f2b3bd6c6bc2..0400e211aa44 100644
> > --- a/include/linux/srcutree.h
> > +++ b/include/linux/srcutree.h
> > @@ -24,25 +24,75 @@
> ...
> > +/*
> > + * Per-SRCU-domain structure, similar in function to rcu_state.
> > + */
> >  struct srcu_struct {
> > -   unsigned long completed;
> > -   unsigned long srcu_gp_seq;
> > -   atomic_t srcu_exp_cnt;
> > -   struct srcu_array __percpu *per_cpu_ref;
> > -   spinlock_t queue_lock; /* protect ->srcu_cblist */
> > -   struct rcu_segcblist srcu_cblist;
> > +   struct srcu_node node[NUM_RCU_NODES];   /* Combining tree. */
> > +   struct srcu_node *level[RCU_NUM_LVLS + 1];
> > +   /* First node at each level. */
> > +   struct mutex srcu_cb_mutex; /* Serialize CB preparation. */
> > +   spinlock_t gp_lock; /* protect ->srcu_cblist */
> > +   struct mutex srcu_gp_mutex; /* Serialize GP work. */
> > +   unsigned int srcu_idx;  /* Current rdr array element. */
> > +   unsigned long srcu_gp_seq;  /* Grace-period seq #. */
> > +   unsigned long srcu_gp_seq_needed;   /* Latest gp_seq needed. */
> > +   atomic_t srcu_exp_cnt;  /* # ongoing expedited GPs. */
> > +   struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */
> > +   unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */
> > +   struct mutex srcu_barrier_mutex;/* Serialize barrier ops. */
> > +   struct completion srcu_barrier_completion;
> > +   /* Awaken barrier rq at end. */
> > +   atomic_t srcu_barrier_cpu_cnt;  /* # CPUs not yet posting a */
> > +   /*  callback for the barrier */
> > +   /*  operation. */
> 
> This change seems to have had the non-obvious effect of breaking the
> powerpc KVM build.
> 
> Because struct kvm contains two srcu_structs which are located
> before the kvm_arch struct, the increase in size of srcu_struct has
> caused the offset from the start of struct kvm to kvm_arch to be too big
> for some of our asm.
> 
> struct kvm {
>   spinlock_t mmu_lock;
>   struct mutex slots_lock;
>   struct mm_struct *mm; /* userspace tied to this vm */
>   struct kvm_memslots *memslots[KVM_ADDRESS_SPACE_NUM];
>   struct srcu_struct srcu;
>   struct srcu_struct irq_srcu;
> ...
>   struct kvm_arch arch;
> 
> 
> Example error:
>   arch/powerpc/kvm/book3s_hv_rmhandlers.S:617: Error: operand out of range 
> (0xb328 is not between 0x8000 and 0x7fff)
> 
> Where line 617 is:
>   lwz r7,KVM_LPID(r9)
> 
> And the KVM_LPID constant comes from asm-offsets.s. The diff of old vs
> new is:
> 
>   -->KVM_LPID 17752 offsetof(struct kvm, arch.lpid)#
>   +->KVM_LPID 45864 offsetof(struct kvm, arch.lpid)#
> 
> 
> We can probably just fix it by changing the asm to keep the address of
> kvm_arch in a register, and then offset from that.

Ouch!

What do you need from me?

Thanx, Paul

powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-19 Thread Michael Ellerman 
"Paul E. McKenney"  writes:

> diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
> index f2b3bd6c6bc2..0400e211aa44 100644
> --- a/include/linux/srcutree.h
> +++ b/include/linux/srcutree.h
> @@ -24,25 +24,75 @@
...
> +/*
> + * Per-SRCU-domain structure, similar in function to rcu_state.
> + */
>  struct srcu_struct {
> - unsigned long completed;
> - unsigned long srcu_gp_seq;
> - atomic_t srcu_exp_cnt;
> - struct srcu_array __percpu *per_cpu_ref;
> - spinlock_t queue_lock; /* protect ->srcu_cblist */
> - struct rcu_segcblist srcu_cblist;
> + struct srcu_node node[NUM_RCU_NODES];   /* Combining tree. */
> + struct srcu_node *level[RCU_NUM_LVLS + 1];
> + /* First node at each level. */
> + struct mutex srcu_cb_mutex; /* Serialize CB preparation. */
> + spinlock_t gp_lock; /* protect ->srcu_cblist */
> + struct mutex srcu_gp_mutex; /* Serialize GP work. */
> + unsigned int srcu_idx;  /* Current rdr array element. */
> + unsigned long srcu_gp_seq;  /* Grace-period seq #. */
> + unsigned long srcu_gp_seq_needed;   /* Latest gp_seq needed. */
> + atomic_t srcu_exp_cnt;  /* # ongoing expedited GPs. */
> + struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */
> + unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */
> + struct mutex srcu_barrier_mutex;/* Serialize barrier ops. */
> + struct completion srcu_barrier_completion;
> + /* Awaken barrier rq at end. */
> + atomic_t srcu_barrier_cpu_cnt;  /* # CPUs not yet posting a */
> + /*  callback for the barrier */
> + /*  operation. */

This change seems to have had the non-obvious effect of breaking the
powerpc KVM build.

Because struct kvm contains two srcu_structs which are located
before the kvm_arch struct, the increase in size of srcu_struct has
caused the offset from the start of struct kvm to kvm_arch to be too big
for some of our asm.

struct kvm {
spinlock_t mmu_lock;
struct mutex slots_lock;
struct mm_struct *mm; /* userspace tied to this vm */
struct kvm_memslots *memslots[KVM_ADDRESS_SPACE_NUM];
struct srcu_struct srcu;
struct srcu_struct irq_srcu;
...
struct kvm_arch arch;


Example error:
  arch/powerpc/kvm/book3s_hv_rmhandlers.S:617: Error: operand out of range 
(0xb328 is not between 0x8000 and 0x7fff)

Where line 617 is:
  lwz   r7,KVM_LPID(r9)

And the KVM_LPID constant comes from asm-offsets.s. The diff of old vs
new is:

  -->KVM_LPID 17752 offsetof(struct kvm, arch.lpid)  #
  +->KVM_LPID 45864 offsetof(struct kvm, arch.lpid)  #


We can probably just fix it by changing the asm to keep the address of
kvm_arch in a register, and then offset from that.

cheers

powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

2017-04-19 Thread Michael Ellerman 
"Paul E. McKenney"  writes:

> diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
> index f2b3bd6c6bc2..0400e211aa44 100644
> --- a/include/linux/srcutree.h
> +++ b/include/linux/srcutree.h
> @@ -24,25 +24,75 @@
...
> +/*
> + * Per-SRCU-domain structure, similar in function to rcu_state.
> + */
>  struct srcu_struct {
> - unsigned long completed;
> - unsigned long srcu_gp_seq;
> - atomic_t srcu_exp_cnt;
> - struct srcu_array __percpu *per_cpu_ref;
> - spinlock_t queue_lock; /* protect ->srcu_cblist */
> - struct rcu_segcblist srcu_cblist;
> + struct srcu_node node[NUM_RCU_NODES];   /* Combining tree. */
> + struct srcu_node *level[RCU_NUM_LVLS + 1];
> + /* First node at each level. */
> + struct mutex srcu_cb_mutex; /* Serialize CB preparation. */
> + spinlock_t gp_lock; /* protect ->srcu_cblist */
> + struct mutex srcu_gp_mutex; /* Serialize GP work. */
> + unsigned int srcu_idx;  /* Current rdr array element. */
> + unsigned long srcu_gp_seq;  /* Grace-period seq #. */
> + unsigned long srcu_gp_seq_needed;   /* Latest gp_seq needed. */
> + atomic_t srcu_exp_cnt;  /* # ongoing expedited GPs. */
> + struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */
> + unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */
> + struct mutex srcu_barrier_mutex;/* Serialize barrier ops. */
> + struct completion srcu_barrier_completion;
> + /* Awaken barrier rq at end. */
> + atomic_t srcu_barrier_cpu_cnt;  /* # CPUs not yet posting a */
> + /*  callback for the barrier */
> + /*  operation. */

This change seems to have had the non-obvious effect of breaking the
powerpc KVM build.

Because struct kvm contains two srcu_structs which are located
before the kvm_arch struct, the increase in size of srcu_struct has
caused the offset from the start of struct kvm to kvm_arch to be too big
for some of our asm.

struct kvm {
spinlock_t mmu_lock;
struct mutex slots_lock;
struct mm_struct *mm; /* userspace tied to this vm */
struct kvm_memslots *memslots[KVM_ADDRESS_SPACE_NUM];
struct srcu_struct srcu;
struct srcu_struct irq_srcu;
...
struct kvm_arch arch;


Example error:
  arch/powerpc/kvm/book3s_hv_rmhandlers.S:617: Error: operand out of range 
(0xb328 is not between 0x8000 and 0x7fff)

Where line 617 is:
  lwz   r7,KVM_LPID(r9)

And the KVM_LPID constant comes from asm-offsets.s. The diff of old vs
new is:

  -->KVM_LPID 17752 offsetof(struct kvm, arch.lpid)  #
  +->KVM_LPID 45864 offsetof(struct kvm, arch.lpid)  #


We can probably just fix it by changing the asm to keep the address of
kvm_arch in a register, and then offset from that.

cheers