Re: [PATCH Part2 v5 21/45] KVM: SVM: Make AVIC backing, VMSA and VMCB memory allocation SNP safe

[Marc Orr]

On Thu, Sep 23, 2021 at 1:44 PM Brijesh Singh <brijesh.singh@xxxxxxx> wrote:
>
>
> On 9/23/21 2:17 PM, Marc Orr wrote:
>
> >>>> +
> >>>> +struct page *snp_safe_alloc_page(struct kvm_vcpu *vcpu)
> >>>> +{
> >>>> +    unsigned long pfn;
> >>>> +    struct page *p;
> >>>> +
> >>>> +    if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
> >>>> +            return alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
> > Continuing my other comment, above: if we introduce a
> > `snp_globally_enabled` var, we could use that here, rather than
> > `cpu_feature_enabled(X86_FEATURE_SEV_SNP)`.
>
>
> Maybe I am missing something, what is wrong with
> cpu_feature_enabled(...) check ? It's same as creating a global
> variable. The feature enabled bit is not set if the said is not
> enabled.  See the patch #3 [1] in this series.
>
> [1]
> https://lore.kernel.org/linux-mm/YUN+L0dlFMbC3bd4@xxxxxxx/T/#m2ac1242b33abfcd0d9fb22a89f4c103eacf67ea7
>
> thanks

You are right. Patch #3 does exactly what I was asking for in
`snp_rmptable_init()`. Thanks!