linux-kernel - [PATCH 0/3] KVM: support the cpu feature FLUSH

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Date:   Wed,  1 Feb 2023 08:29:02 -0500
From:   Emanuele Giuseppe Esposito <eesposit@...hat.com>
To:     kvm@...r.kernel.org
Cc:     Jim Mattson <jmattson@...gle.com>,
        Ben Serebrin <serebrin@...gle.com>,
        Peter Shier <pshier@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Maxim Levitsky <mlevitsk@...hat.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        Emanuele Giuseppe Esposito <eesposit@...hat.com>
Subject: [PATCH 0/3] KVM: support the cpu feature FLUSH_L1D

As the title suggest, if the host cpu supports flush_l1d flag and
QEMU/userspace wants to boot a VM with the same flag (or emulate same
host features), KVM should be able to do so.

Patch 3 is the main fix, because if flush_l1d is not advertised by
KVM, a linux VM will erroneously mark
/sys/devices/system/cpu/vulnerabilities/mmio_stale_data
as vulnerable, even though it isn't since the host has the feature
and takes care of this. Not sure what would happen in the nested case though.

Patch 1 and 2 are just taken and refactored from Jim Mattison's serie that it
seems was lost a while ago:
https://patchwork.kernel.org/project/kvm/patch/20180814173049.21756-1-jmattson@google.com/

I thought it was worth re-posting them.

Thank you,
Emanuele

Emanuele Giuseppe Esposito (3):
  kvm: vmx: Add IA32_FLUSH_CMD guest support
  kvm: svm: Add IA32_FLUSH_CMD guest support
  kvm: x86: Advertise FLUSH_L1D to user space

 arch/x86/kvm/cpuid.c      |  2 +-
 arch/x86/kvm/svm/svm.c    | 44 ++++++++++++++++--------
 arch/x86/kvm/vmx/nested.c |  3 ++
 arch/x86/kvm/vmx/vmx.c    | 70 +++++++++++++++++++++++++--------------
 4 files changed, 80 insertions(+), 39 deletions(-)

-- 
2.39.1