Hi Dongjiu Geng, On 28/08/17 11:38, Dongjiu Geng wrote: > In ARMV8.2 RAS extension, a virtual SError exception syndrome > register(VSESR_EL2) is added. This value may be specified from > userspace. I agree that the CPU support for injecting SErrors with a specified ESR should be exposed to KVM's user space... > Userspace will want to check if the CPU has the RAS > extension. ... but user-space wants to know if it can inject SErrors with a specified ESR. What if we gain another way of doing this that isn't via the RAS-extensions, now user-space has to check for two capabilities. > If it has, it wil specify the virtual SError syndrome > value, otherwise it will not be set. This patch adds support for > querying the availability of this extension. I'm against telling user-space what features the CPU has unless it can use them directly. In this case we are talking about a KVM API, so we should describe the API not the CPU. > diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c > index 3256b9228e75..b7313ee028e9 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_RAS_EXTENSION: This should be called something more like '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; We can inject SError on systems without the RAS extensions using just the HCR_EL2.VSE bit. We may want to make the 'ESR' part of the API optional, or expose '1' for the without-ESR version and '2 for with-ESR, (however we choose to implement that). The risk is if we want to add a without-ESR version later, and the name we make ABI now turned out to be a mistake. Marc or Christoffer probably have the best view of this. (no-one has needed it so far...) Thanks, James -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
