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

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Date:   Tue, 28 Apr 2020 16:10:23 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        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: [PATCH 0/2] KVM: nVMX: vmcs.SYSENTER optimization and "fix"

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(-)

-- 
2.26.0