[PATCH] KVM: PPC: fix ONE_REG AltiVec support

[Greg Kurz]

The get and set operations got exchanged by mistake when moving the
code from book3s.c to powerpc.c.

Fixes: 3840edc8033ad5b86deee309c1c321ca54257452
Signed-off-by: Greg Kurz 
---

It's been there for over a year but I guess we want that in 4.4, even
if doesn't break the host kernel.

 arch/powerpc/kvm/powerpc.c |   20 ++--
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 6fd2405c7f4a..a3b182dcb823 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -919,21 +919,17 @@ int kvm_vcpu_ioctl_get_one_reg(struct kvm_vcpu *vcpu, 
struct kvm_one_reg *reg)
r = -ENXIO;
break;
}
-   vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0] = val.vval;
+   val.vval = vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0];
break;
case KVM_REG_PPC_VSCR:
if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
r = -ENXIO;
break;
}
-   vcpu->arch.vr.vscr.u[3] = set_reg_val(reg->id, val);
+   val = get_reg_val(reg->id, vcpu->arch.vr.vscr.u[3]);
break;
case KVM_REG_PPC_VRSAVE:
-   if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
-   r = -ENXIO;
-   break;
-   }
-   vcpu->arch.vrsave = set_reg_val(reg->id, val);
+   val = get_reg_val(reg->id, vcpu->arch.vrsave);
break;
 #endif /* CONFIG_ALTIVEC */
default:
@@ -974,17 +970,21 @@ int kvm_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu, 
struct kvm_one_reg *reg)
r = -ENXIO;
break;
}
-   val.vval = vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0];
+   vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0] = val.vval;
break;
case KVM_REG_PPC_VSCR:
if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
r = -ENXIO;
break;
}
-   val = get_reg_val(reg->id, vcpu->arch.vr.vscr.u[3]);
+   vcpu->arch.vr.vscr.u[3] = set_reg_val(reg->id, val);
break;
case KVM_REG_PPC_VRSAVE:
-   val = get_reg_val(reg->id, vcpu->arch.vrsave);
+   if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
+   r = -ENXIO;
+   break;
+   }
+   vcpu->arch.vrsave = set_reg_val(reg->id, val);
break;
 #endif /* CONFIG_ALTIVEC */
default:

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Re: [PATCH v2] KVM: PPC: Exit guest upon fatal machine check exception

[Aravinda Prasad]

On Thursday 17 December 2015 08:02 AM, David Gibson wrote:
> On Wed, Dec 16, 2015 at 11:26:12AM +0530, Aravinda Prasad wrote:
>> This patch modifies KVM to cause a guest exit with
>> KVM_EXIT_NMI instead of immediately delivering a 0x200
>> interrupt to guest upon machine check exception in
>> guest address. Exiting the guest enables QEMU to build
>> error log and deliver machine check exception to guest
>> OS (either via guest OS registered machine check
>> handler or via 0x200 guest OS interrupt vector).
>>
>> This approach simplifies the delivering of machine
>> check exception to guest OS compared to the earlier approach
>> of KVM directly invoking 0x200 guest interrupt vector.
>> In the earlier approach QEMU patched the 0x200 interrupt
>> vector during boot. The patched code at 0x200 issued a
>> private hcall to pass the control to QEMU to build the
>> error log.
>>
>> This design/approach is based on the feedback for the
>> QEMU patches to handle machine check exception. Details
>> of earlier approach of handling machine check exception
>> in QEMU and related discussions can be found at:
>>
>> https://lists.nongnu.org/archive/html/qemu-devel/2014-11/msg00813.html
>>
>> This patch also introduces a new KVM capability to
>> control how KVM behaves on machine check exception.
>> Without this capability, KVM redirects machine check
>> exceptions to guest's 0x200 vector if the address in
>> error belongs to guest. With this capability KVM
>> causes a guest exit with NMI exit reason.
>>
>> This is required to avoid problems if a new kernel/KVM
>> is used with an old QEMU for guests that don't issue
>> "ibm,nmi-register". As old QEMU does not understand the
>> NMI exit type, it treats it as a fatal error. However,
>> the guest could have handled the machine check error
>> if the exception was delivered to guest's 0x200 interrupt
>> vector instead of NMI exit in case of old QEMU.
>>
>> Change Log v2:
>>   - Added KVM capability
>>
>> Signed-off-by: Aravinda Prasad 
>> ---
>>  arch/powerpc/include/asm/kvm_host.h |1 +
>>  arch/powerpc/kernel/asm-offsets.c   |1 +
>>  arch/powerpc/kvm/book3s_hv.c|   12 +++---
>>  arch/powerpc/kvm/book3s_hv_rmhandlers.S |   37 
>> +++
>>  arch/powerpc/kvm/powerpc.c  |7 ++
>>  include/uapi/linux/kvm.h|1 +
>>  6 files changed, 31 insertions(+), 28 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/kvm_host.h 
>> b/arch/powerpc/include/asm/kvm_host.h
>> index 827a38d..8a652ba 100644
>> --- a/arch/powerpc/include/asm/kvm_host.h
>> +++ b/arch/powerpc/include/asm/kvm_host.h
>> @@ -243,6 +243,7 @@ struct kvm_arch {
>>  int hpt_cma_alloc;
>>  struct dentry *debugfs_dir;
>>  struct dentry *htab_dentry;
>> +u8 fwnmi_enabled;
>>  #endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */
>>  #ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE
>>  struct mutex hpt_mutex;
>> diff --git a/arch/powerpc/kernel/asm-offsets.c 
>> b/arch/powerpc/kernel/asm-offsets.c
>> index 221d584..6a4e81a 100644
>> --- a/arch/powerpc/kernel/asm-offsets.c
>> +++ b/arch/powerpc/kernel/asm-offsets.c
>> @@ -506,6 +506,7 @@ int main(void)
>>  DEFINE(KVM_ENABLED_HCALLS, offsetof(struct kvm, arch.enabled_hcalls));
>>  DEFINE(KVM_LPCR, offsetof(struct kvm, arch.lpcr));
>>  DEFINE(KVM_VRMA_SLB_V, offsetof(struct kvm, arch.vrma_slb_v));
>> +DEFINE(KVM_FWNMI, offsetof(struct kvm, arch.fwnmi_enabled));
>>  DEFINE(VCPU_DSISR, offsetof(struct kvm_vcpu, arch.shregs.dsisr));
>>  DEFINE(VCPU_DAR, offsetof(struct kvm_vcpu, arch.shregs.dar));
>>  DEFINE(VCPU_VPA, offsetof(struct kvm_vcpu, arch.vpa.pinned_addr));
>> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
>> index 2280497..1b1dff0 100644
>> --- a/arch/powerpc/kvm/book3s_hv.c
>> +++ b/arch/powerpc/kvm/book3s_hv.c
>> @@ -859,15 +859,9 @@ static int kvmppc_handle_exit_hv(struct kvm_run *run, 
>> struct kvm_vcpu *vcpu,
>>  r = RESUME_GUEST;
>>  break;
>>  case BOOK3S_INTERRUPT_MACHINE_CHECK:
>> -/*
>> - * Deliver a machine check interrupt to the guest.
>> - * We have to do this, even if the host has handled the
>> - * machine check, because machine checks use SRR0/1 and
>> - * the interrupt might have trashed guest state in them.
>> - */
>> -kvmppc_book3s_queue_irqprio(vcpu,
>> -BOOK3S_INTERRUPT_MACHINE_CHECK);
>> -r = RESUME_GUEST;
>> +/* Exit to guest with KVM_EXIT_NMI as exit reason */
>> +run->exit_reason = KVM_EXIT_NMI;
>> +r = RESUME_HOST;
>>  break;
>>  case BOOK3S_INTERRUPT_PROGRAM:
>>  {
>> diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S 
>> b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
>> index b98889e..f43c124 100644
>> --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
>> +++ 

Re: [PATCH v2] KVM: PPC: Exit guest upon fatal machine check exception

[David Gibson]

On Wed, Dec 16, 2015 at 11:26:12AM +0530, Aravinda Prasad wrote:
> This patch modifies KVM to cause a guest exit with
> KVM_EXIT_NMI instead of immediately delivering a 0x200
> interrupt to guest upon machine check exception in
> guest address. Exiting the guest enables QEMU to build
> error log and deliver machine check exception to guest
> OS (either via guest OS registered machine check
> handler or via 0x200 guest OS interrupt vector).
> 
> This approach simplifies the delivering of machine
> check exception to guest OS compared to the earlier approach
> of KVM directly invoking 0x200 guest interrupt vector.
> In the earlier approach QEMU patched the 0x200 interrupt
> vector during boot. The patched code at 0x200 issued a
> private hcall to pass the control to QEMU to build the
> error log.
> 
> This design/approach is based on the feedback for the
> QEMU patches to handle machine check exception. Details
> of earlier approach of handling machine check exception
> in QEMU and related discussions can be found at:
> 
> https://lists.nongnu.org/archive/html/qemu-devel/2014-11/msg00813.html
> 
> This patch also introduces a new KVM capability to
> control how KVM behaves on machine check exception.
> Without this capability, KVM redirects machine check
> exceptions to guest's 0x200 vector if the address in
> error belongs to guest. With this capability KVM
> causes a guest exit with NMI exit reason.
> 
> This is required to avoid problems if a new kernel/KVM
> is used with an old QEMU for guests that don't issue
> "ibm,nmi-register". As old QEMU does not understand the
> NMI exit type, it treats it as a fatal error. However,
> the guest could have handled the machine check error
> if the exception was delivered to guest's 0x200 interrupt
> vector instead of NMI exit in case of old QEMU.
> 
> Change Log v2:
>   - Added KVM capability
> 
> Signed-off-by: Aravinda Prasad 
> ---
>  arch/powerpc/include/asm/kvm_host.h |1 +
>  arch/powerpc/kernel/asm-offsets.c   |1 +
>  arch/powerpc/kvm/book3s_hv.c|   12 +++---
>  arch/powerpc/kvm/book3s_hv_rmhandlers.S |   37 
> +++
>  arch/powerpc/kvm/powerpc.c  |7 ++
>  include/uapi/linux/kvm.h|1 +
>  6 files changed, 31 insertions(+), 28 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/kvm_host.h 
> b/arch/powerpc/include/asm/kvm_host.h
> index 827a38d..8a652ba 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -243,6 +243,7 @@ struct kvm_arch {
>   int hpt_cma_alloc;
>   struct dentry *debugfs_dir;
>   struct dentry *htab_dentry;
> + u8 fwnmi_enabled;
>  #endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */
>  #ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE
>   struct mutex hpt_mutex;
> diff --git a/arch/powerpc/kernel/asm-offsets.c 
> b/arch/powerpc/kernel/asm-offsets.c
> index 221d584..6a4e81a 100644
> --- a/arch/powerpc/kernel/asm-offsets.c
> +++ b/arch/powerpc/kernel/asm-offsets.c
> @@ -506,6 +506,7 @@ int main(void)
>   DEFINE(KVM_ENABLED_HCALLS, offsetof(struct kvm, arch.enabled_hcalls));
>   DEFINE(KVM_LPCR, offsetof(struct kvm, arch.lpcr));
>   DEFINE(KVM_VRMA_SLB_V, offsetof(struct kvm, arch.vrma_slb_v));
> + DEFINE(KVM_FWNMI, offsetof(struct kvm, arch.fwnmi_enabled));
>   DEFINE(VCPU_DSISR, offsetof(struct kvm_vcpu, arch.shregs.dsisr));
>   DEFINE(VCPU_DAR, offsetof(struct kvm_vcpu, arch.shregs.dar));
>   DEFINE(VCPU_VPA, offsetof(struct kvm_vcpu, arch.vpa.pinned_addr));
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 2280497..1b1dff0 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -859,15 +859,9 @@ static int kvmppc_handle_exit_hv(struct kvm_run *run, 
> struct kvm_vcpu *vcpu,
>   r = RESUME_GUEST;
>   break;
>   case BOOK3S_INTERRUPT_MACHINE_CHECK:
> - /*
> -  * Deliver a machine check interrupt to the guest.
> -  * We have to do this, even if the host has handled the
> -  * machine check, because machine checks use SRR0/1 and
> -  * the interrupt might have trashed guest state in them.
> -  */
> - kvmppc_book3s_queue_irqprio(vcpu,
> - BOOK3S_INTERRUPT_MACHINE_CHECK);
> - r = RESUME_GUEST;
> + /* Exit to guest with KVM_EXIT_NMI as exit reason */
> + run->exit_reason = KVM_EXIT_NMI;
> + r = RESUME_HOST;
>   break;
>   case BOOK3S_INTERRUPT_PROGRAM:
>   {
> diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S 
> b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> index b98889e..f43c124 100644
> --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> @@ -147,7 +147,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
>   addir1, r1, 112

Re: [PATCH v2] KVM: PPC: Exit guest upon fatal machine check exception

[Aravinda Prasad]

On Wednesday 16 December 2015 03:10 PM, Thomas Huth wrote:
> On 16/12/15 06:56, Aravinda Prasad wrote:
>> This patch modifies KVM to cause a guest exit with
>> KVM_EXIT_NMI instead of immediately delivering a 0x200
>> interrupt to guest upon machine check exception in
>> guest address. Exiting the guest enables QEMU to build
>> error log and deliver machine check exception to guest
>> OS (either via guest OS registered machine check
>> handler or via 0x200 guest OS interrupt vector).
>>
>> This approach simplifies the delivering of machine
>> check exception to guest OS compared to the earlier approach
>> of KVM directly invoking 0x200 guest interrupt vector.
>> In the earlier approach QEMU patched the 0x200 interrupt
>> vector during boot. The patched code at 0x200 issued a
>> private hcall to pass the control to QEMU to build the
>> error log.
>>
>> This design/approach is based on the feedback for the
>> QEMU patches to handle machine check exception. Details
>> of earlier approach of handling machine check exception
>> in QEMU and related discussions can be found at:
>>
>> https://lists.nongnu.org/archive/html/qemu-devel/2014-11/msg00813.html
>>
>> This patch also introduces a new KVM capability to
>> control how KVM behaves on machine check exception.
>> Without this capability, KVM redirects machine check
>> exceptions to guest's 0x200 vector if the address in
>> error belongs to guest. With this capability KVM
>> causes a guest exit with NMI exit reason.
>>
>> This is required to avoid problems if a new kernel/KVM
>> is used with an old QEMU for guests that don't issue
>> "ibm,nmi-register". As old QEMU does not understand the
>> NMI exit type, it treats it as a fatal error. However,
>> the guest could have handled the machine check error
>> if the exception was delivered to guest's 0x200 interrupt
>> vector instead of NMI exit in case of old QEMU.
>>
>> Change Log v2:
>>   - Added KVM capability
>>
>> Signed-off-by: Aravinda Prasad 
>> ---
>>  arch/powerpc/include/asm/kvm_host.h |1 +
>>  arch/powerpc/kernel/asm-offsets.c   |1 +
>>  arch/powerpc/kvm/book3s_hv.c|   12 +++---
>>  arch/powerpc/kvm/book3s_hv_rmhandlers.S |   37 
>> +++
>>  arch/powerpc/kvm/powerpc.c  |7 ++
>>  include/uapi/linux/kvm.h|1 +
>>  6 files changed, 31 insertions(+), 28 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/kvm_host.h 
>> b/arch/powerpc/include/asm/kvm_host.h
>> index 827a38d..8a652ba 100644
>> --- a/arch/powerpc/include/asm/kvm_host.h
>> +++ b/arch/powerpc/include/asm/kvm_host.h
>> @@ -243,6 +243,7 @@ struct kvm_arch {
>>  int hpt_cma_alloc;
>>  struct dentry *debugfs_dir;
>>  struct dentry *htab_dentry;
>> +u8 fwnmi_enabled;
> 
> Here you declare the variable as 8-bits ...
> 
>>  #endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */
>>  #ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE
>>  struct mutex hpt_mutex;
>> diff --git a/arch/powerpc/kernel/asm-offsets.c 
>> b/arch/powerpc/kernel/asm-offsets.c
>> index 221d584..6a4e81a 100644
>> --- a/arch/powerpc/kernel/asm-offsets.c
>> +++ b/arch/powerpc/kernel/asm-offsets.c
>> @@ -506,6 +506,7 @@ int main(void)
>>  DEFINE(KVM_ENABLED_HCALLS, offsetof(struct kvm, arch.enabled_hcalls));
>>  DEFINE(KVM_LPCR, offsetof(struct kvm, arch.lpcr));
>>  DEFINE(KVM_VRMA_SLB_V, offsetof(struct kvm, arch.vrma_slb_v));
>> +DEFINE(KVM_FWNMI, offsetof(struct kvm, arch.fwnmi_enabled));
> 
> ... then define an asm-offset for it ...
> 
>>  DEFINE(VCPU_DSISR, offsetof(struct kvm_vcpu, arch.shregs.dsisr));
>>  DEFINE(VCPU_DAR, offsetof(struct kvm_vcpu, arch.shregs.dar));
>>  DEFINE(VCPU_VPA, offsetof(struct kvm_vcpu, arch.vpa.pinned_addr));
>> diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S 
>> b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
>> index b98889e..f43c124 100644
>> --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
>> +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> [...]
>> @@ -2381,24 +2377,27 @@ machine_check_realmode:
>>  ld  r9, HSTATE_KVM_VCPU(r13)
>>  li  r12, BOOK3S_INTERRUPT_MACHINE_CHECK
>>  /*
>> - * Deliver unhandled/fatal (e.g. UE) MCE errors to guest through
>> - * machine check interrupt (set HSRR0 to 0x200). And for handled
>> - * errors (no-fatal), just go back to guest execution with current
>> - * HSRR0 instead of exiting guest. This new approach will inject
>> - * machine check to guest for fatal error causing guest to crash.
>> - *
>> - * The old code used to return to host for unhandled errors which
>> - * was causing guest to hang with soft lockups inside guest and
>> - * makes it difficult to recover guest instance.
>> + * Deliver unhandled/fatal (e.g. UE) MCE errors to guest
>> + * by exiting the guest with KVM_EXIT_NMI exit reason (exit
>> + * reason set later based on trap). For handled errors
>> + * (no-fatal), go back to guest 

Re: [PATCH v2] KVM: PPC: Exit guest upon fatal machine check exception

[Thomas Huth]

On 16/12/15 06:56, Aravinda Prasad wrote:
> This patch modifies KVM to cause a guest exit with
> KVM_EXIT_NMI instead of immediately delivering a 0x200
> interrupt to guest upon machine check exception in
> guest address. Exiting the guest enables QEMU to build
> error log and deliver machine check exception to guest
> OS (either via guest OS registered machine check
> handler or via 0x200 guest OS interrupt vector).
> 
> This approach simplifies the delivering of machine
> check exception to guest OS compared to the earlier approach
> of KVM directly invoking 0x200 guest interrupt vector.
> In the earlier approach QEMU patched the 0x200 interrupt
> vector during boot. The patched code at 0x200 issued a
> private hcall to pass the control to QEMU to build the
> error log.
> 
> This design/approach is based on the feedback for the
> QEMU patches to handle machine check exception. Details
> of earlier approach of handling machine check exception
> in QEMU and related discussions can be found at:
> 
> https://lists.nongnu.org/archive/html/qemu-devel/2014-11/msg00813.html
> 
> This patch also introduces a new KVM capability to
> control how KVM behaves on machine check exception.
> Without this capability, KVM redirects machine check
> exceptions to guest's 0x200 vector if the address in
> error belongs to guest. With this capability KVM
> causes a guest exit with NMI exit reason.
> 
> This is required to avoid problems if a new kernel/KVM
> is used with an old QEMU for guests that don't issue
> "ibm,nmi-register". As old QEMU does not understand the
> NMI exit type, it treats it as a fatal error. However,
> the guest could have handled the machine check error
> if the exception was delivered to guest's 0x200 interrupt
> vector instead of NMI exit in case of old QEMU.
> 
> Change Log v2:
>   - Added KVM capability
> 
> Signed-off-by: Aravinda Prasad 
> ---
>  arch/powerpc/include/asm/kvm_host.h |1 +
>  arch/powerpc/kernel/asm-offsets.c   |1 +
>  arch/powerpc/kvm/book3s_hv.c|   12 +++---
>  arch/powerpc/kvm/book3s_hv_rmhandlers.S |   37 
> +++
>  arch/powerpc/kvm/powerpc.c  |7 ++
>  include/uapi/linux/kvm.h|1 +
>  6 files changed, 31 insertions(+), 28 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/kvm_host.h 
> b/arch/powerpc/include/asm/kvm_host.h
> index 827a38d..8a652ba 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -243,6 +243,7 @@ struct kvm_arch {
>   int hpt_cma_alloc;
>   struct dentry *debugfs_dir;
>   struct dentry *htab_dentry;
> + u8 fwnmi_enabled;

Here you declare the variable as 8-bits ...

>  #endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */
>  #ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE
>   struct mutex hpt_mutex;
> diff --git a/arch/powerpc/kernel/asm-offsets.c 
> b/arch/powerpc/kernel/asm-offsets.c
> index 221d584..6a4e81a 100644
> --- a/arch/powerpc/kernel/asm-offsets.c
> +++ b/arch/powerpc/kernel/asm-offsets.c
> @@ -506,6 +506,7 @@ int main(void)
>   DEFINE(KVM_ENABLED_HCALLS, offsetof(struct kvm, arch.enabled_hcalls));
>   DEFINE(KVM_LPCR, offsetof(struct kvm, arch.lpcr));
>   DEFINE(KVM_VRMA_SLB_V, offsetof(struct kvm, arch.vrma_slb_v));
> + DEFINE(KVM_FWNMI, offsetof(struct kvm, arch.fwnmi_enabled));

... then define an asm-offset for it ...

>   DEFINE(VCPU_DSISR, offsetof(struct kvm_vcpu, arch.shregs.dsisr));
>   DEFINE(VCPU_DAR, offsetof(struct kvm_vcpu, arch.shregs.dar));
>   DEFINE(VCPU_VPA, offsetof(struct kvm_vcpu, arch.vpa.pinned_addr));
> diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S 
> b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> index b98889e..f43c124 100644
> --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
[...]
> @@ -2381,24 +2377,27 @@ machine_check_realmode:
>   ld  r9, HSTATE_KVM_VCPU(r13)
>   li  r12, BOOK3S_INTERRUPT_MACHINE_CHECK
>   /*
> -  * Deliver unhandled/fatal (e.g. UE) MCE errors to guest through
> -  * machine check interrupt (set HSRR0 to 0x200). And for handled
> -  * errors (no-fatal), just go back to guest execution with current
> -  * HSRR0 instead of exiting guest. This new approach will inject
> -  * machine check to guest for fatal error causing guest to crash.
> -  *
> -  * The old code used to return to host for unhandled errors which
> -  * was causing guest to hang with soft lockups inside guest and
> -  * makes it difficult to recover guest instance.
> +  * Deliver unhandled/fatal (e.g. UE) MCE errors to guest
> +  * by exiting the guest with KVM_EXIT_NMI exit reason (exit
> +  * reason set later based on trap). For handled errors
> +  * (no-fatal), go back to guest execution with current HSRR0
> +  * instead of exiting the guest. This approach will cause
> +  * the guest to exit in case of fatal