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

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

[...]

quoted

+
+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.

quoted

+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

quoted

+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

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