From: Gleb Natapov <gleb@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Arthur Chunqi Li <yzt356@gmail.com>,
kvm@vger.kernel.org, jan.kiszka@web.de, yang.z.zhang@intel.com
Subject: Re: [PATCH v4] KVM: nVMX: Fully support of nested VMX preemption timer
Date: Mon, 16 Sep 2013 12:09:11 +0300 [thread overview]
Message-ID: <20130916090911.GL17294@redhat.com> (raw)
In-Reply-To: <5236C824.8090700@redhat.com>
On Mon, Sep 16, 2013 at 10:58:12AM +0200, Paolo Bonzini wrote:
> >>> vmx->__launched = vmx->loaded_vmcs->launched;
> >>> + if (is_guest_mode(vcpu) && !(vmx->nested.nested_vmx_exit))
> >>> + nested_adjust_preemption_timer(vcpu);
> >>
> >> Please leave the assignment to __launched last, since it's already
> >> initializing the asm below.
> >>
> >> I don't like the is_guest_mode check here... Maybe it's
> >> micro-optimizing, but I wonder if we already do too many checks in
> >> vmx_vcpu_run... For example, is_guest_mode could be changed (I think)
> >> to a check for "vmx->loaded_vmcs == &vmx->vmcs1".
> >>
> > Why this will be more efficient that HF_GUEST_MASK check?
>
> Because we have already loaded vmx->loaded_vmcs, so it's one memory
> access less.
>
But we will have to load vmx->vmcs1 instead :) Looks like very minor
optimization if at all. If we could avoid additional if() at all
somehow, may be mimicking vcpu->requests in vmx to get rid of most ifs
there.
--
Gleb.
next prev parent reply other threads:[~2013-09-16 9:09 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-06 2:04 [PATCH v4] KVM: nVMX: Fully support of nested VMX preemption timer Arthur Chunqi Li
2013-09-13 17:15 ` Paolo Bonzini
2013-09-14 7:44 ` Jan Kiszka
2013-09-15 7:59 ` Arthur Chunqi Li
2013-09-16 5:42 ` Arthur Chunqi Li
2013-09-16 7:18 ` Jan Kiszka
2013-09-16 7:44 ` Gleb Natapov
2013-09-16 8:58 ` Paolo Bonzini
2013-09-16 9:09 ` Gleb Natapov [this message]
2013-09-16 9:49 ` Paolo Bonzini
2013-09-16 10:44 ` Gleb Natapov
2013-09-16 10:50 ` Paolo Bonzini
2013-09-15 12:31 ` Gleb Natapov
2013-09-16 5:49 ` Arthur Chunqi Li
2013-09-16 6:20 ` Gleb Natapov
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