linux-kernel - Re: [PATCH 0/2] KVM: nVMX: vmcs.SYSENTER optimization and "fix"

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Message-ID: <61ba7eb0-4c51-0001-1d99-ef1478750c78@redhat.com>
Date:   Mon, 4 May 2020 19:03:17 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.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
Subject: Re: [PATCH 0/2] KVM: nVMX: vmcs.SYSENTER optimization and "fix"

On 29/04/20 01:10, Sean Christopherson wrote:
> Patch 1 is a "fix" for handling SYSENTER_EIP/ESP in L2 on a 32-bit vCPU.
> The primary motivation is to provide consistent behavior after patch 2.
> 
> Patch 2 is essentially a re-submission of a nested VMX optimization to
> avoid redundant VMREADs to the SYSENTER fields in the nested VM-Exit path.
> 
> After patch 2 and without patch 1, KVM would end up with weird behavior
> where L1 and L2 would only see 32-bit values for their own SYSENTER_E*P
> MSRs, but L1 could see a 64-bit value for L2's MSRs.
> 
> Sean Christopherson (2):
>   KVM: nVMX: Truncate writes to vmcs.SYSENTER_EIP/ESP for 32-bit vCPU
>   KVM: nVMX: Drop superfluous VMREAD of vmcs02.GUEST_SYSENTER_*
> 
>  arch/x86/kvm/vmx/nested.c |  4 ----
>  arch/x86/kvm/vmx/vmx.c    | 18 ++++++++++++++++--
>  2 files changed, 16 insertions(+), 6 deletions(-)
> 

Queued, thanks.

Paolo