Hi gengdongjiu, On 12/06/18 16:48, gengdongjiu wrote: > On 2018/6/12 23:29, James Morse wrote: >> On 12/06/18 15:50, gengdongjiu wrote: >>> On 2018/6/11 21:36, James Morse wrote: >>>> On 08/06/18 20:48, Dongjiu Geng wrote: >>>>> diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h >>>>> index caae484..c3e6975 100644 >>>>> --- a/arch/arm/include/uapi/asm/kvm.h >>>>> +++ b/arch/arm/include/uapi/asm/kvm.h >>>>> @@ -124,6 +124,18 @@ struct kvm_sync_regs { >>>>> struct kvm_arch_memory_slot { >>>>> }; >>>>> >>>>> +/* for KVM_GET/SET_VCPU_EVENTS */ >>>>> +struct kvm_vcpu_events { >>>>> + struct { >>>>> + __u8 serror_pending; >>>>> + __u8 serror_has_esr; >>>>> + /* Align it to 8 bytes */ >>>>> + __u8 pad[6]; >>>>> + __u64 serror_esr; >>>>> + } exception; >>>>> + __u32 reserved[12]; >>>>> +}; >>>>> + >>>> >>>> You haven't defined __KVM_HAVE_VCPU_EVENTS for 32bit, so presumably this struct >>>> will never be used. Why is it here? >> >>> if not add it for 32 bits. the 32 arm platform will build Fail, whether you have good >>> idea to avoid this Failure if not add this struct for the 32 bit? >> >> How does this 32bit code build without this patch? >> If do you provide the struct, how will that code build with older headers? >> >> As far as I can see, this is what the __KVM_HAVE_VCPU_EVENTS define is for. >> >> This should be both, or neither. Having just the struct is useless. > It because the caller of kvm_arm_vcpu_get/set_events() is in "virt/kvm/arm/arm.c". > the virt/kvm/arm/arm.c will used by both arm64 and arm. > so It needs to add kvm_arm_vcpu_get/set_events() for the 32 bits, however, kvm_arm_vcpu_get/set_events() will directly return, So you are adding a uapi struct that user-space can't actually use, to avoid a kernel build-error. Fine, it just looks really strange. 32bit user-space shouldn't try to call this as check-extension reports it as not present. If it does, it gets -EINVAL back, which is also the default for kvm_arch_vcpu_ioctl(). 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