linux-kernel - Re: [PATCH] KVM: x86: Don't treat ENTER and LEAVE as branches, because they aren't

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Message-ID: <CALMp9eRAqb0HSt_kpWefUuYmcdvqohBzdx9EsurRcA9o3SfqpA@mail.gmail.com>
Date: Fri, 19 Sep 2025 09:22:03 -0700
From: Jim Mattson <jmattson@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: Don't treat ENTER and LEAVE as branches,
 because they aren't

On Thu, Sep 18, 2025 at 5:46 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> Remove the IsBranch flag from ENTER and LEAVE in KVM's emulator, as ENTER
> and LEAVE are stack operations, not branches.  Add forced emulation of
> said instructions to the PMU counters test to prove that KVM diverges from
> hardware, and to guard against regressions.
>
> Fixes: 018d70ffcfec ("KVM: x86: Update vPMCs when retiring branch instructions")
> Cc: Jim Mattson <jmattson@...gle.com>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Jim Mattson <jmattson@...gle.com>