linux-kernel - [PATCH v2 0/2] ] KVM: SVM: Track physical cpu and asid

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Message-Id: <20210113141019.5127-1-cavery@redhat.com>
Date:   Wed, 13 Jan 2021 09:10:17 -0500
From:   Cathy Avery <cavery@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        pbonzini@...hat.com
Cc:     vkuznets@...hat.com, wei.huang2@....com
Subject: [PATCH v2 0/2] ] KVM: SVM: Track physical cpu and asid_generation via the vmcb

In the cases where vmcbs change processors from one vmrun to another updated
information in the vmcb from a prior run can potentially be lost. By tracking
the physical cpu and asid_generation per vmcb instead of svm->vcpu the following
scenario illustrated by Paolo can be avoided.

     ---------------------          ---------------------
     pCPU 1                         pCPU 2
     ---------------------          ---------------------
     run VMCB02
                                    run VMCB02 (*)
                                    run VMCB01
     run VMCB01 (**)
     run VMCB02 (***)
     ---------------------          ---------------------

     After the point marked (*), while L2 runs, some fields change in VMCB02.
     When the processor vmexits back to L0, VMCB02 is marked clean.

     At the point marked (**), svm->vcpu.cpu becomes 1 again.

     Therefore, at the point marked (***) you will get svm->vcpu.cpu == cpu
     and the VMCB02 will not be marked dirty.  The processor can then incorrectly
     use some data that is cached from before point (*).

Theses patches are intended for the kvm nested-svm branch.

The patches have been tested on nested fedora VMs, kvm self tests, and kvm-unit-tests.
They have not been tested on SEV.

Changes v1 -> v2:
- Remove outdated comment from svm_switch_vmcb().

Cathy Avery (2):
  KVM: nSVM: Track the physical cpu of the vmcb vmrun through the vmcb
  KVM: nSVM: Track the ASID generation of the vmcb vmrun through the
    vmcb

 arch/x86/kvm/svm/svm.c | 40 ++++++++++++++++++++--------------------
 arch/x86/kvm/svm/svm.h |  3 ++-
 2 files changed, 22 insertions(+), 21 deletions(-)

-- 
2.20.1