Re: [PATCH v10 2/5] arm64: KVM: export the capability to set guest SError syndrome

Re: [PATCH v10 2/5] arm64: KVM: export the capability to set guest SError syndrome

[gengdongjiu]

Hi James,
   Thanks for your time to review and give comments.

[...]
> > +
> > +8.14 KVM_CAP_ARM_SET_SERROR_ESR
> > +
> > +Architectures: arm, arm64
> > +
> > +This capability indicates that userspace can specify syndrome value
> > +reported to guest OS when guest takes a virtual SError interrupt exception.
> 
> "when userspace triggers a virtual SError"... how?

In the user space(QEMU), it will call kvm_arch_put_registers() or kvm_arch_get_registers() to set or get KVM registers through KVM_SET_ONE_REG/ KVM_GET_ONE_REG IOCTL, at the same time the two functions will separately call kvm_arm_vcpu_get_events() and kvm_arm_vcpu_set_events() to get/set vcpu events. If user space want to trigger a virtual SError with specified ESR, it only need to setup the kvm_vcpu_events struct(exception.serror_pending = 1; exception.serror_has_esr=1; serror_esr=xxxxx), then KVM will trigger this virtual SError.

userspace can trigger it at any time, for example, for debug purpose.  Or simulate a SError after recording a CPER for guest. But before triggering a virtual SError, it needs to know whether KVM has such capability, so KVM needs to export this capability to user space. If has this capability, User space will call kvm_arm_vcpu_set_events() to trigger a virtual SError.

> 
> 
> > +If KVM has this capability, userspace can only specify the ISS field
> > +for the ESR syndrome, can not specify the EC field which is not under control by KVM.
> 
> Where do I put the ESR?
> If you re-order this after the patch that adds the API, you can describe how this can be used.

Ok, thank a lot for your suggestion.

> 
> 
> Thanks,
> 
> James
> 
> 
> 
> > +If this virtual SError is taken to EL1 using AArch64, this value will
> > +be reported into ISS filed of ESR_EL1.
> > diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c index
> > 3256b92..38c8a64 100644
> > --- a/arch/arm64/kvm/reset.c
> > +++ b/arch/arm64/kvm/reset.c
> > @@ -77,6 +77,9 @@ int kvm_arch_dev_ioctl_check_extension(struct kvm *kvm, long ext)
> >  	case KVM_CAP_ARM_PMU_V3:
> >  		r = kvm_arm_support_pmu_v3();
> >  		break;
> > +	case KVM_CAP_ARM_INJECT_SERROR_ESR:
> > +		r = cpus_have_const_cap(ARM64_HAS_RAS_EXTN);
> > +		break;
> >  	case KVM_CAP_SET_GUEST_DEBUG:
> >  	case KVM_CAP_VCPU_ATTRIBUTES:
> >  		r = 1;
> > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index
> > 8fb90a0..3587b33 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -934,6 +934,7 @@ struct kvm_ppc_resize_hpt {  #define
> > KVM_CAP_S390_AIS_MIGRATION 150  #define KVM_CAP_PPC_GET_CPU_CHAR 151
> > #define KVM_CAP_S390_BPB 152
> > +#define KVM_CAP_ARM_INJECT_SERROR_ESR 153
> >
> >  #ifdef KVM_CAP_IRQ_ROUTING
> >
> >

Re: [PATCH v10 2/5] arm64: KVM: export the capability to set guest SError syndrome

[James Morse]

Hi Dongjiu Geng,

On 03/03/18 16:09, Dongjiu Geng wrote:
> Before user space injects a SError, it needs to know whether it can
> specify the guest Exception Syndrome, so KVM should tell user space
> whether it has such capability.

> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index fc3ae95..8a3d708 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -4415,3 +4415,14 @@ Parameters: none
>  This capability indicates if the flic device will be able to get/set the
>  AIS states for migration via the KVM_DEV_FLIC_AISM_ALL attribute and allows
>  to discover this without having to create a flic device.
> +
> +8.14 KVM_CAP_ARM_SET_SERROR_ESR
> +
> +Architectures: arm, arm64
> +
> +This capability indicates that userspace can specify syndrome value reported to
> +guest OS when guest takes a virtual SError interrupt exception.

"when userspace triggers a virtual SError"... how?


> +If KVM has this capability, userspace can only specify the ISS field for the ESR
> +syndrome, can not specify the EC field which is not under control by KVM.

Where do I put the ESR?
If you re-order this after the patch that adds the API, you can describe how
this can be used.


Thanks,

James



> +If this virtual SError is taken to EL1 using AArch64, this value will be reported
> +into ISS filed of ESR_EL1.
> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index 3256b92..38c8a64 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
> @@ -77,6 +77,9 @@ int kvm_arch_dev_ioctl_check_extension(struct kvm *kvm, long ext)
>  	case KVM_CAP_ARM_PMU_V3:
>  		r = kvm_arm_support_pmu_v3();
>  		break;
> +	case KVM_CAP_ARM_INJECT_SERROR_ESR:
> +		r = cpus_have_const_cap(ARM64_HAS_RAS_EXTN);
> +		break;
>  	case KVM_CAP_SET_GUEST_DEBUG:
>  	case KVM_CAP_VCPU_ATTRIBUTES:
>  		r = 1;
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 8fb90a0..3587b33 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -934,6 +934,7 @@ struct kvm_ppc_resize_hpt {
>  #define KVM_CAP_S390_AIS_MIGRATION 150
>  #define KVM_CAP_PPC_GET_CPU_CHAR 151
>  #define KVM_CAP_S390_BPB 152
> +#define KVM_CAP_ARM_INJECT_SERROR_ESR 153
>  
>  #ifdef KVM_CAP_IRQ_ROUTING
>  
> 

[PATCH v10 2/5] arm64: KVM: export the capability to set guest SError syndrome

[Dongjiu Geng]

Before user space injects a SError, it needs to know whether it can
specify the guest Exception Syndrome, so KVM should tell user space
whether it has such capability.

Signed-off-by: Dongjiu Geng <gengdongjiu@huawei.com>
---
 Documentation/virtual/kvm/api.txt | 11 +++++++++++
 arch/arm64/kvm/reset.c            |  3 +++
 include/uapi/linux/kvm.h          |  1 +
 3 files changed, 15 insertions(+)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index fc3ae95..8a3d708 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -4415,3 +4415,14 @@ Parameters: none
 This capability indicates if the flic device will be able to get/set the
 AIS states for migration via the KVM_DEV_FLIC_AISM_ALL attribute and allows
 to discover this without having to create a flic device.
+
+8.14 KVM_CAP_ARM_SET_SERROR_ESR
+
+Architectures: arm, arm64
+
+This capability indicates that userspace can specify syndrome value reported to
+guest OS when guest takes a virtual SError interrupt exception.
+If KVM has this capability, userspace can only specify the ISS field for the ESR
+syndrome, can not specify the EC field which is not under control by KVM.
+If this virtual SError is taken to EL1 using AArch64, this value will be reported
+into ISS filed of ESR_EL1.
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 3256b92..38c8a64 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -77,6 +77,9 @@ int kvm_arch_dev_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_ARM_PMU_V3:
 		r = kvm_arm_support_pmu_v3();
 		break;
+	case KVM_CAP_ARM_INJECT_SERROR_ESR:
+		r = cpus_have_const_cap(ARM64_HAS_RAS_EXTN);
+		break;
 	case KVM_CAP_SET_GUEST_DEBUG:
 	case KVM_CAP_VCPU_ATTRIBUTES:
 		r = 1;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 8fb90a0..3587b33 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -934,6 +934,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_S390_AIS_MIGRATION 150
 #define KVM_CAP_PPC_GET_CPU_CHAR 151
 #define KVM_CAP_S390_BPB 152
+#define KVM_CAP_ARM_INJECT_SERROR_ESR 153
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
1.9.1