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Subject: Re: [PATCH Part2 v5 21/45] KVM: SVM: Make AVIC backing, VMSA and VMCB
 memory allocation SNP safe
To:     Marc Orr <marcorr@google.com>
Cc:     "Dr. David Alan Gilbert" <dgilbert@redhat.com>,
        x86 <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
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From:   Brijesh Singh <brijesh.singh@amd.com>
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Date:   Thu, 23 Sep 2021 15:44:28 -0500
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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@zn.tnic/T/#m2ac1242b33abfcd0d9fb22a89f4c103eacf67ea7

thanks