linux-kernel - Re: [PATCH] KVM: VMX: Remove unnecessary INVEPT[GLOBAL] from hardware enable path

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Message-ID: <171961446147.237951.4273132233545629028.b4-ty@google.com>
Date: Fri, 28 Jun 2024 15:55:42 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: VMX: Remove unnecessary INVEPT[GLOBAL] from hardware
 enable path

On Fri, 07 Jun 2024 17:10:03 -0700, Sean Christopherson wrote:
> Remove the completely pointess global INVEPT, i.e. EPT TLB flush, from
> KVM's VMX enablement path.  KVM always does a targeted TLB flush when
> using a "new" EPT root, in quotes because "new" simply means a root that
> isn't currently being used by the vCPU.
> 
> KVM also _deliberately_ runs with stale TLB entries for defunct roots,
> i.e. doesn't do a TLB flush when vCPUs stop using roots, precisely because
> KVM does the flush on first use.  As called out by the comment in
> kvm_mmu_load(), the reason KVM flushes on first use is because KVM can't
> guarantee the correctness of past hypervisors.
> 
> [...]

Applied to kvm-x86 vmx, thanks!

[1/1] KVM: VMX: Remove unnecessary INVEPT[GLOBAL] from hardware enable path
      https://github.com/kvm-x86/linux/commit/23b2c5088d01

--
https://github.com/kvm-x86/linux/tree/next