From: Sean Christopherson <seanjc@google.com>
To: Oliver Upton <oupton@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org, Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>
Subject: Re: [PATCH v2 1/7] KVM: nVMX: Keep KVM updates to BNDCFGS ctrl bits across MSR write
Date: Mon, 7 Feb 2022 18:34:19 +0000 [thread overview]
Message-ID: <YgFmK2ZIh2wSQTnr@google.com> (raw)
In-Reply-To: <YgFjaY18suUJjkLL@google.com>
On Mon, Feb 07, 2022, Oliver Upton wrote:
> Until recently, this all sort of 'worked'. Since we called
> kvm_update_cpuid() all the time it was possible for KVM to overwrite the
> bits after the MSR write, just not immediately so. After the whole CPUID
> rework, we only update the VMX control MSRs immediately after a
> KVM_SET_CPUID2, meaning we've missed the case of MSR write after CPUID.
That needs to be explained in the changelog (ditto for patch 02), and arguably
the Fixes tag is wrong too, or at least incomplete. The commit that truly broke
things was
aedbaf4f6afd ("KVM: x86: Extract kvm_update_cpuid_runtime() from kvm_update_cpuid()")
I'm guessing this is why Paolo is also confused. Without understanding that KVM
used too (eventually) enforce its overrides, it looks like you're proposing an
arbitrary, unnecessary ABI change.
next prev parent reply other threads:[~2022-02-07 18:35 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-04 20:46 [PATCH v2 0/7] VMX: nVMX: VMX control MSR fixes Oliver Upton
2022-02-04 20:46 ` [PATCH v2 1/7] KVM: nVMX: Keep KVM updates to BNDCFGS ctrl bits across MSR write Oliver Upton
2022-02-07 17:21 ` Paolo Bonzini
2022-02-07 18:13 ` Sean Christopherson
2022-02-07 18:22 ` Oliver Upton
2022-02-07 18:27 ` Paolo Bonzini
2022-02-07 18:34 ` Sean Christopherson [this message]
2022-02-07 18:52 ` Oliver Upton
2022-02-04 20:47 ` [PATCH v2 2/7] KVM: nVMX: Keep KVM updates to PERF_GLOBAL_CTRL " Oliver Upton
2022-02-07 16:33 ` Paolo Bonzini
2022-02-04 20:47 ` [PATCH v2 3/7] KVM: nVMX: Roll all entry/exit ctl updates into a single helper Oliver Upton
2022-02-05 7:43 ` kernel test robot
2022-02-05 19:41 ` Oliver Upton
2022-02-07 17:56 ` Sean Christopherson
2022-02-04 20:47 ` [PATCH v2 4/7] KVM: nVMX: Add a quirk for KVM tweaks to VMX control MSRs Oliver Upton
2022-02-07 18:06 ` Sean Christopherson
2022-02-09 1:50 ` Oliver Upton
2022-02-09 20:23 ` Sean Christopherson
2022-02-04 20:47 ` [PATCH v2 5/7] selftests: KVM: Add test for PERF_GLOBAL_CTRL VMX control MSR bits Oliver Upton
2022-02-04 20:47 ` [PATCH v2 6/7] selftests: KVM: Add test for BNDCFGS " Oliver Upton
2022-02-07 16:42 ` Paolo Bonzini
2022-02-04 20:47 ` [PATCH v2 7/7] KVM: VMX: Use local pointer to vcpu_vmx in vmx_vcpu_after_set_cpuid() Oliver Upton
2022-02-07 16:42 ` Paolo Bonzini
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