linux-kernel - Re: [PATCH v4 0/4] KVM: x86: Fix and harden reg caching from !TASK context

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Message-ID: <ZyUrwCeIyaNE310v@google.com>
Date: Fri, 1 Nov 2024 12:28:00 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Maxim Levitsky <mlevitsk@...hat.com>
Subject: Re: [PATCH v4 0/4] KVM: x86: Fix and harden reg caching from !TASK context

On Thu, Oct 31, 2024, Sean Christopherson wrote:
> On Wed, 09 Oct 2024 10:49:58 -0700, Sean Christopherson wrote:
> > Fix a (VMX only) bug reported by Maxim where KVM caches a stale SS.AR_BYTES
> > when involuntary preemption schedules out a vCPU during vmx_vcpu_rest(), and
> > ultimately clobbers the VMCS's SS.AR_BYTES if userspace does KVM_GET_SREGS
> > => KVM_SET_SREGS, i.e. if userspace writes the stale value back into KVM.
> > 
> > v4, as this is a spiritual successor to Maxim's earlier series.
> > 
> > [...]
> 
> Applied 1 and 3-4 to kvm-x86 misc.  Patch 2 went into 6.12.  Thanks!
> 
> [1/4] KVM: x86: Bypass register cache when querying CPL from kvm_sched_out()
>       https://github.com/kvm-x86/linux/commit/8c8e90f79c56
> [2/4] KVM: VMX: reset the segment cache after segment init in vmx_vcpu_reset()
>       (no commit info)
> [3/4] KVM: x86: Add lockdep-guarded asserts on register cache usage
>       https://github.com/kvm-x86/linux/commit/21abefc6958d
> [4/4] KVM: x86: Use '0' for guest RIP if PMI encounters protected guest state
>       https://github.com/kvm-x86/linux/commit/a395d143ef40

FYI, I rebased misc to v6.12-rc5, as patches in another series had already been
taken through the tip tree.  New hashes:

[1/4] KVM: x86: Bypass register cache when querying CPL from kvm_sched_out()
      https://github.com/kvm-x86/linux/commit/f0e7012c4b93
...

[3/4] KVM: x86: Add lockdep-guarded asserts on register cache usage
      https://github.com/kvm-x86/linux/commit/1c932fc7620d
[4/4] KVM: x86: Use '0' for guest RIP if PMI encounters protected guest state
      https://github.com/kvm-x86/linux/commit/eecf3985459a