From: Quan Xu <quan.xu0@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: wanpeng.li@hotmail.com
Subject: Re: [PATCH] KVM: x86: avoid unnecessary XSETBV on guest entry
Date: Thu, 14 Dec 2017 11:27:27 +0800 [thread overview]
Message-ID: <f22b5190-2beb-5b2a-02ec-dbad5f0a8a7d@gmail.com> (raw)
In-Reply-To: <1513169512-28139-1-git-send-email-pbonzini@redhat.com>
On 2017/12/13 20:51, Paolo Bonzini wrote:
> xsetbv can be expensive when running on nested virtualization, try to
> avoid it.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> arch/x86/kvm/x86.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 0f82e2cbf64c..daa1918031df 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -702,7 +702,8 @@ static void kvm_load_guest_xcr0(struct kvm_vcpu *vcpu)
> if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE) &&
> !vcpu->guest_xcr0_loaded) {
> /* kvm_set_xcr() also depends on this */
> - xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.xcr0);
> + if (vcpu->arch.xcr0 != host_xcr0)
> + xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.xcr0);
> vcpu->guest_xcr0_loaded = 1;
> }
> }
Reviewed-by: Quan Xu <quan.xu0@gmail.com>
prev parent reply other threads:[~2017-12-14 3:27 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-13 12:51 Paolo Bonzini
2017-12-13 19:03 ` Jim Mattson
2017-12-14 1:05 ` Wanpeng Li
2017-12-14 3:27 ` Quan Xu [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=f22b5190-2beb-5b2a-02ec-dbad5f0a8a7d@gmail.com \
--to=quan.xu0@gmail.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=wanpeng.li@hotmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®