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SubjectRe: [PATCH 2/2] KVM: x86: Allow userspace to define what's the microcode version
2017-11-27 0:41 GMT+08:00 Filippo Sironi <sironi@amazon.de>:
> ... that the guest should see.
> Guest operating systems may check the microcode version to decide whether
> to disable certain features that are known to be buggy up to certain
> microcode versions. Address the issue by making the microcode version
> that the guest should see settable.
> The rationale for having userspace specifying the microcode version, rather
> than having the kernel picking it, is to ensure consistency for live-migrated
> instances; we don't want them to see a microcode version increase without a
> reset.

Is there a scenario which needs to refresh the microcode in the guest
instead of on the host?

Regards,
Wanpeng Li

>
> Signed-off-by: Filippo Sironi <sironi@amazon.de>
> ---
> arch/x86/kvm/x86.c | 23 +++++++++++++++++++++++
> include/uapi/linux/kvm.h | 3 +++
> 2 files changed, 26 insertions(+)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 925c3e29cad3..741588f27ebc 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4033,6 +4033,29 @@ long kvm_arch_vm_ioctl(struct file *filp,
> } u;
>
> switch (ioctl) {
> + case KVM_GET_MICROCODE_VERSION: {
> + r = -EFAULT;
> + if (copy_to_user(argp,
> + &kvm->arch.microcode_version,
> + sizeof(kvm->arch.microcode_version)))
> + goto out;
> + break;
> + }
> + case KVM_SET_MICROCODE_VERSION: {
> + u32 microcode_version;
> +
> + r = -EFAULT;
> + if (copy_from_user(&microcode_version,
> + argp,
> + sizeof(microcode_version)))
> + goto out;
> + r = -EINVAL;
> + if (!microcode_version)
> + goto out;
> + kvm->arch.microcode_version = microcode_version;
> + r = 0;
> + break;
> + }
> case KVM_SET_TSS_ADDR:
> r = kvm_vm_ioctl_set_tss_addr(kvm, arg);
> break;
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 282d7613fce8..e11887758e29 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1192,6 +1192,9 @@ struct kvm_s390_ucas_mapping {
> #define KVM_S390_UCAS_UNMAP _IOW(KVMIO, 0x51, struct kvm_s390_ucas_mapping)
> #define KVM_S390_VCPU_FAULT _IOW(KVMIO, 0x52, unsigned long)
>
> +#define KVM_GET_MICROCODE_VERSION _IOR(KVMIO, 0x5e, __u32)
> +#define KVM_SET_MICROCODE_VERSION _IOW(KVMIO, 0x5f, __u32)
> +
> /* Device model IOC */
> #define KVM_CREATE_IRQCHIP _IO(KVMIO, 0x60)
> #define KVM_IRQ_LINE _IOW(KVMIO, 0x61, struct kvm_irq_level)
> --
> 2.7.4
>

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