From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Jim Mattson <jmattson@google.com>
Cc: kvm list <kvm@vger.kernel.org>,
Liran Alon <liran.alon@oracle.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Dan Cross <dcross@google.com>, Peter Shier <pshier@google.com>
Subject: Re: [PATCH v4] KVM: nVMX: Don't leak L1 MMIO regions to L2
Date: Tue, 15 Oct 2019 10:32:17 -0700 [thread overview]
Message-ID: <20191015173217.GH15015@linux.intel.com> (raw)
In-Reply-To: <CALMp9eQ-xcQSESs7et3voPU7-Jbs6X14S1U74_izYCSpyNbstg@mail.gmail.com>
On Tue, Oct 15, 2019 at 10:13:06AM -0700, Jim Mattson wrote:
> On Mon, Oct 14, 2019 at 6:07 PM Sean Christopherson
> <sean.j.christopherson@intel.com> wrote:
> > KVM doesn't usually add (un)likely annotations for things that are under
> > L1's control. The "unlikely(vmx->fail)" in nested_vmx_exit_reflected() is
> > there because it's true iff KVM missed a VM-Fail condition that was caught
> > by hardware.
>
> I would argue that it makes sense to optimize for the success path in
> this case. If L1 is taking the failure path more frequently than the
> success path, something is wrong. Moreover, you have already indicated
> that the success path should be statically predicted taken by asking
> me to move the failure path out-of-line. (Forward conditional branches
> are statically predicted not taken, per section 3.4.1.3 of the Intel
> 64 and IA-32 Architectures Optimization Reference Manual.) I'm just
> asking the compiler not to undo that hint.
Fair enough.
prev parent reply other threads:[~2019-10-15 17:32 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-15 0:13 [PATCH v4] KVM: nVMX: Don't leak L1 MMIO regions to L2 Jim Mattson
2019-10-15 1:07 ` Sean Christopherson
2019-10-15 17:13 ` Jim Mattson
2019-10-15 17:32 ` Sean Christopherson [this message]
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