linux-kernel - Re: [PATCH 2/2] KVM: SEV: Fall back to __vmalloc() for SEV-ES scratch area if necessary

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Date:   Thu, 11 Nov 2021 13:52:07 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [PATCH 2/2] KVM: SEV: Fall back to __vmalloc() for SEV-ES scratch
 area if necessary

On 11/9/21 23:23, Sean Christopherson wrote:
> The buffer is purely a KVM software construct, i.e. there's
> no need for it to be physically contiguous, and at a max allowed size of
> 16kb it's just large enough that kzalloc() could feasibly fail due to
> memory fragmentation.

That isn't entirely correct, as kzalloc() won't really fail for requests 
up to 32kb, i.e. order <= PAGE_ALLOC_COSTLY_ORDER.  However, the 
reasoning is correct so I queued the patches.

Paolo