Re: [Xen-devel] [PATCH v1] x86/hvm: Add MSR old value

[Wei Liu]

On Thu, Oct 12, 2017 at 12:10:25PM +0300, Alexandru Isaila wrote:
> This patch adds the old value param and the onchangeonly option
> to the VM_EVENT_REASON_MOV_TO_MSR event.
> 
> The param was added to the vm_event_mov_to_msr struct and to the
> hvm_monitor_msr function. Finally I've changed the bool_t param
> to a bool for the hvm_msr_write_intercept function.
> 
> Signed-off-by: Alexandru Isaila 
> ---
>  tools/libxc/include/xenctrl.h |  2 +-
>  tools/libxc/xc_monitor.c  |  3 ++-

Acked-by: Wei Liu 

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Re: [Xen-devel] [PATCH v1] x86/hvm: Add MSR old value

[Tamas K Lengyel]

On Fri, Oct 13, 2017 at 6:17 AM, Jan Beulich  wrote:
 On 13.10.17 at 12:36,  wrote:
>> On 13.10.2017 13:29, Jan Beulich wrote:
 +__set_bit(index + sizeof(struct monitor_msr_bitmap), bitmap);
>>>
>>> I think you miss "* 8" here - a bit position plus sizeof() doesn't
>>> produce any useful value.
>>>
>>> But what's worse - having read till the end of the patch I don't
>>> see you change any allocation, yet you clearly need to double
>>> the space now that you need two bits per MSR.
>>
>> We did this:
>>
>> diff --git a/xen/arch/x86/monitor.c b/xen/arch/x86/monitor.c
>> index e59f1f5..a3046c6 100644
>> --- a/xen/arch/x86/monitor.c
>> +++ b/xen/arch/x86/monitor.c
>> @@ -25,7 +25,7 @@
>>   int arch_monitor_init_domain(struct domain *d)
>>   {
>>   if ( !d->arch.monitor.msr_bitmap )
>> -d->arch.monitor.msr_bitmap = xzalloc(struct monitor_msr_bitmap);
>> +d->arch.monitor.msr_bitmap = xzalloc_array(struct 
>> monitor_msr_bitmap, 2);
>>
>>   if ( !d->arch.monitor.msr_bitmap )
>>   return -ENOMEM;
>> @@ -67,7 +67,7 @@ static unsigned long *monitor_bitmap_for_msr(const struct 
>> domain *d, u32 *msr)
>>   }
>>   }
>>
>> I.e., we are now allocating an array of size 2 of struct
>> monitor_msr_bitmaps with xzalloc_array().
>
> Oh, I'm not sure how I could overlook this considering that I
> specifically looked up the allocation point and searched through
> the patch for a respective change. I'm sorry for the noise in
> this regard. I do think though that the chosen model is a little
> odd and fragile, but that's something you and Tamas as the
> maintainers of the code have to judge about.
>

It looks fine to me.

Thanks,
Tamas

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Re: [Xen-devel] [PATCH v1] x86/hvm: Add MSR old value

[Jan Beulich]

>>> On 13.10.17 at 12:36,  wrote:
> On 13.10.2017 13:29, Jan Beulich wrote:
>>> +__set_bit(index + sizeof(struct monitor_msr_bitmap), bitmap);
>> 
>> I think you miss "* 8" here - a bit position plus sizeof() doesn't
>> produce any useful value.
>> 
>> But what's worse - having read till the end of the patch I don't
>> see you change any allocation, yet you clearly need to double
>> the space now that you need two bits per MSR.
> 
> We did this:
> 
> diff --git a/xen/arch/x86/monitor.c b/xen/arch/x86/monitor.c
> index e59f1f5..a3046c6 100644
> --- a/xen/arch/x86/monitor.c
> +++ b/xen/arch/x86/monitor.c
> @@ -25,7 +25,7 @@
>   int arch_monitor_init_domain(struct domain *d)
>   {
>   if ( !d->arch.monitor.msr_bitmap )
> -d->arch.monitor.msr_bitmap = xzalloc(struct monitor_msr_bitmap);
> +d->arch.monitor.msr_bitmap = xzalloc_array(struct 
> monitor_msr_bitmap, 2);
> 
>   if ( !d->arch.monitor.msr_bitmap )
>   return -ENOMEM;
> @@ -67,7 +67,7 @@ static unsigned long *monitor_bitmap_for_msr(const struct 
> domain *d, u32 *msr)
>   }
>   }
> 
> I.e., we are now allocating an array of size 2 of struct 
> monitor_msr_bitmaps with xzalloc_array().

Oh, I'm not sure how I could overlook this considering that I
specifically looked up the allocation point and searched through
the patch for a respective change. I'm sorry for the noise in
this regard. I do think though that the chosen model is a little
odd and fragile, but that's something you and Tamas as the
maintainers of the code have to judge about.

Jan


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Re: [Xen-devel] [PATCH v1] x86/hvm: Add MSR old value

[Razvan Cojocaru]

On 13.10.2017 13:29, Jan Beulich wrote:

+__set_bit(index + sizeof(struct monitor_msr_bitmap), bitmap);


I think you miss "* 8" here - a bit position plus sizeof() doesn't
produce any useful value.

But what's worse - having read till the end of the patch I don't
see you change any allocation, yet you clearly need to double
the space now that you need two bits per MSR.


We did this:

diff --git a/xen/arch/x86/monitor.c b/xen/arch/x86/monitor.c
index e59f1f5..a3046c6 100644
--- a/xen/arch/x86/monitor.c
+++ b/xen/arch/x86/monitor.c
@@ -25,7 +25,7 @@
 int arch_monitor_init_domain(struct domain *d)
 {
 if ( !d->arch.monitor.msr_bitmap )
-d->arch.monitor.msr_bitmap = xzalloc(struct monitor_msr_bitmap);
+d->arch.monitor.msr_bitmap = xzalloc_array(struct 
monitor_msr_bitmap, 2);


 if ( !d->arch.monitor.msr_bitmap )
 return -ENOMEM;
@@ -67,7 +67,7 @@ static unsigned long *monitor_bitmap_for_msr(const 
struct domain *d, u32 *msr)

 }
 }

I.e., we are now allocating an array of size 2 of struct 
monitor_msr_bitmaps with xzalloc_array().



Thanks,
Razvan

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Re: [Xen-devel] [PATCH v1] x86/hvm: Add MSR old value

[Jan Beulich]

>>> On 12.10.17 at 11:10,  wrote:
> --- a/xen/arch/x86/hvm/monitor.c
> +++ b/xen/arch/x86/hvm/monitor.c
> @@ -74,16 +74,19 @@ bool hvm_monitor_emul_unimplemented(void)
>  monitor_traps(curr, true, ) == 1;
>  }
>  
> -void hvm_monitor_msr(unsigned int msr, uint64_t value)
> +void hvm_monitor_msr(unsigned int msr, uint64_t new_value, uint64_t 
> old_value)
>  {
>  struct vcpu *curr = current;
>  
> -if ( monitored_msr(curr->domain, msr) )
> +if ( monitored_msr(curr->domain, msr) &&
> + ( !monitored_msr_onchangeonly(curr->domain, msr) ||
> +   new_value != old_value ) )

Stray blanks inside the inner parentheses.

> @@ -84,6 +84,11 @@ static int monitor_enable_msr(struct domain *d, u32 msr)
>  
>  hvm_enable_msr_interception(d, msr);
>  
> +if( onchangeonly )

Style.

> +__set_bit(index + sizeof(struct monitor_msr_bitmap), bitmap);

I think you miss "* 8" here - a bit position plus sizeof() doesn't
produce any useful value.

But what's worse - having read till the end of the patch I don't
see you change any allocation, yet you clearly need to double
the space now that you need two bits per MSR.

> --- a/xen/include/asm-x86/monitor.h
> +++ b/xen/include/asm-x86/monitor.h
> @@ -105,4 +105,6 @@ void arch_monitor_cleanup_domain(struct domain *d);
>  
>  bool monitored_msr(const struct domain *d, u32 msr);
>  
> +bool monitored_msr_onchangeonly(const struct domain *d, u32 msr);
> +

Them belonging together, please have them together (without an
intervening blank line).

Jan


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Re: [Xen-devel] [PATCH v1] x86/hvm: Add MSR old value

[Tamas K Lengyel]

On Thu, Oct 12, 2017 at 3:10 AM, Alexandru Isaila
 wrote:
> This patch adds the old value param and the onchangeonly option
> to the VM_EVENT_REASON_MOV_TO_MSR event.
>
> The param was added to the vm_event_mov_to_msr struct and to the
> hvm_monitor_msr function. Finally I've changed the bool_t param
> to a bool for the hvm_msr_write_intercept function.
>
> Signed-off-by: Alexandru Isaila 

Acked-by: Tamas K Lengyel 

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[Xen-devel] [PATCH v1] x86/hvm: Add MSR old value

[Alexandru Isaila]

This patch adds the old value param and the onchangeonly option
to the VM_EVENT_REASON_MOV_TO_MSR event.

The param was added to the vm_event_mov_to_msr struct and to the
hvm_monitor_msr function. Finally I've changed the bool_t param
to a bool for the hvm_msr_write_intercept function.

Signed-off-by: Alexandru Isaila 
---
 tools/libxc/include/xenctrl.h |  2 +-
 tools/libxc/xc_monitor.c  |  3 ++-
 xen/arch/x86/hvm/hvm.c| 10 --
 xen/arch/x86/hvm/monitor.c|  9 ++---
 xen/arch/x86/monitor.c| 26 +++---
 xen/include/asm-x86/hvm/monitor.h |  2 +-
 xen/include/asm-x86/hvm/support.h |  2 +-
 xen/include/asm-x86/monitor.h |  2 ++
 xen/include/public/domctl.h   |  2 ++
 xen/include/public/vm_event.h |  5 +++--
 10 files changed, 49 insertions(+), 14 deletions(-)

diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index 3bcab3c..b99d6eb 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -2048,7 +2048,7 @@ int xc_monitor_write_ctrlreg(xc_interface *xch, domid_t 
domain_id,
  * non-architectural indices.
  */
 int xc_monitor_mov_to_msr(xc_interface *xch, domid_t domain_id, uint32_t msr,
-  bool enable);
+  bool enable, bool onchangeonly);
 int xc_monitor_singlestep(xc_interface *xch, domid_t domain_id, bool enable);
 int xc_monitor_software_breakpoint(xc_interface *xch, domid_t domain_id,
bool enable);
diff --git a/tools/libxc/xc_monitor.c b/tools/libxc/xc_monitor.c
index 6046680..09d04be 100644
--- a/tools/libxc/xc_monitor.c
+++ b/tools/libxc/xc_monitor.c
@@ -90,7 +90,7 @@ int xc_monitor_write_ctrlreg(xc_interface *xch, domid_t 
domain_id,
 }
 
 int xc_monitor_mov_to_msr(xc_interface *xch, domid_t domain_id, uint32_t msr,
-  bool enable)
+  bool enable, bool onchangeonly)
 {
 DECLARE_DOMCTL;
 
@@ -100,6 +100,7 @@ int xc_monitor_mov_to_msr(xc_interface *xch, domid_t 
domain_id, uint32_t msr,
 : XEN_DOMCTL_MONITOR_OP_DISABLE;
 domctl.u.monitor_op.event = XEN_DOMCTL_MONITOR_EVENT_MOV_TO_MSR;
 domctl.u.monitor_op.u.mov_to_msr.msr = msr;
+domctl.u.monitor_op.u.mov_to_msr.onchangeonly = onchangeonly;
 
 return do_domctl(xch, );
 }
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 205b4cb..0238787 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3489,7 +3489,7 @@ int hvm_msr_read_intercept(unsigned int msr, uint64_t 
*msr_content)
 }
 
 int hvm_msr_write_intercept(unsigned int msr, uint64_t msr_content,
-bool_t may_defer)
+bool may_defer)
 {
 struct vcpu *v = current;
 struct domain *d = v->domain;
@@ -3500,6 +3500,12 @@ int hvm_msr_write_intercept(unsigned int msr, uint64_t 
msr_content,
 
 if ( may_defer && unlikely(monitored_msr(v->domain, msr)) )
 {
+uint64_t msr_old_content;
+
+ret = hvm_msr_read_intercept(msr, _old_content);
+if ( ret != X86EMUL_OKAY )
+return ret;
+
 ASSERT(v->arch.vm_event);
 
 /* The actual write will occur in hvm_do_resume() (if permitted). */
@@ -3507,7 +3513,7 @@ int hvm_msr_write_intercept(unsigned int msr, uint64_t 
msr_content,
 v->arch.vm_event->write_data.msr = msr;
 v->arch.vm_event->write_data.value = msr_content;
 
-hvm_monitor_msr(msr, msr_content);
+hvm_monitor_msr(msr, msr_content, msr_old_content);
 return X86EMUL_OKAY;
 }
 
diff --git a/xen/arch/x86/hvm/monitor.c b/xen/arch/x86/hvm/monitor.c
index 4ce778c..74f83b4 100644
--- a/xen/arch/x86/hvm/monitor.c
+++ b/xen/arch/x86/hvm/monitor.c
@@ -74,16 +74,19 @@ bool hvm_monitor_emul_unimplemented(void)
 monitor_traps(curr, true, ) == 1;
 }
 
-void hvm_monitor_msr(unsigned int msr, uint64_t value)
+void hvm_monitor_msr(unsigned int msr, uint64_t new_value, uint64_t old_value)
 {
 struct vcpu *curr = current;
 
-if ( monitored_msr(curr->domain, msr) )
+if ( monitored_msr(curr->domain, msr) &&
+ ( !monitored_msr_onchangeonly(curr->domain, msr) ||
+   new_value != old_value ) )
 {
 vm_event_request_t req = {
 .reason = VM_EVENT_REASON_MOV_TO_MSR,
 .u.mov_to_msr.msr = msr,
-.u.mov_to_msr.value = value,
+.u.mov_to_msr.new_value = new_value,
+.u.mov_to_msr.old_value = old_value
 };
 
 monitor_traps(curr, 1, );
diff --git a/xen/arch/x86/monitor.c b/xen/arch/x86/monitor.c
index e59f1f5..a3046c6 100644
--- a/xen/arch/x86/monitor.c
+++ b/xen/arch/x86/monitor.c
@@ -25,7 +25,7 @@
 int arch_monitor_init_domain(struct domain *d)
 {
 if ( !d->arch.monitor.msr_bitmap )
-d->arch.monitor.msr_bitmap = xzalloc(struct monitor_msr_bitmap);
+d->arch.monitor.msr_bitmap =