From: Marcelo Tosatti <mtosatti@redhat.com>
To: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Avi Kivity <avi@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH 2/3] KVM: x86: let reexecute_instruction work for tdp
Date: Tue, 27 Nov 2012 21:32:46 -0200 [thread overview]
Message-ID: <20121127233246.GB8295@amt.cnet> (raw)
In-Reply-To: <50B42FC7.2080805@linux.vnet.ibm.com>
On Tue, Nov 27, 2012 at 11:13:11AM +0800, Xiao Guangrong wrote:
> >> +static bool reexecute_instruction(struct kvm_vcpu *vcpu, unsigned long cr2)
> >> {
> >> - gpa_t gpa;
> >> + gpa_t gpa = cr2;
> >> pfn_t pfn;
> >>
> >> - if (tdp_enabled)
> >> + if (!ACCESS_ONCE(vcpu->kvm->arch.indirect_shadow_pages))
> >> return false;
> >
> > How is indirect_shadow_pages protected? Why is ACCESS_ONCE() being used
> > to read it?
>
> Hi Marcelo,
>
> It is protected by mmu-lock for it only be changed when mmu-lock is hold. And
> ACCESS_ONCE is used on read path avoiding magic optimization from compiler.
Please switch to mmu_lock protection, there is no reason to have access
to this variable locklessly - not performance critical.
For example, there is no use of barriers when modifying the variable.
next prev parent reply other threads:[~2012-11-27 23:42 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-19 23:57 [PATCH 0/3] KVM: x86: improve reexecute_instruction Xiao Guangrong
2012-11-19 23:58 ` [PATCH 1/3] KVM: x86: clean up reexecute_instruction Xiao Guangrong
2012-11-20 12:11 ` Gleb Natapov
2012-11-20 20:13 ` Xiao Guangrong
2012-11-19 23:59 ` [PATCH 2/3] KVM: x86: let reexecute_instruction work for tdp Xiao Guangrong
2012-11-26 22:37 ` Marcelo Tosatti
2012-11-27 3:13 ` Xiao Guangrong
2012-11-27 23:32 ` Marcelo Tosatti [this message]
2012-11-28 3:15 ` Xiao Guangrong
2012-11-28 14:01 ` Gleb Natapov
2012-11-28 14:55 ` Xiao Guangrong
2012-11-28 22:07 ` Marcelo Tosatti
2012-11-19 23:59 ` [PATCH 3/3] KVM: x86: improve reexecute_instruction Xiao Guangrong
2012-11-26 22:41 ` Marcelo Tosatti
2012-11-27 3:30 ` Xiao Guangrong
2012-11-27 23:42 ` Marcelo Tosatti
2012-11-28 3:33 ` Xiao Guangrong
2012-11-28 14:12 ` Gleb Natapov
2012-11-28 14:59 ` Xiao Guangrong
2012-11-28 21:57 ` Marcelo Tosatti
2012-11-28 22:40 ` Xiao Guangrong
2012-11-28 23:16 ` Xiao Guangrong
2012-11-29 0:23 ` Marcelo Tosatti
2012-11-29 0:21 ` Marcelo Tosatti
2012-12-03 8:33 ` Xiao Guangrong
2012-12-03 19:47 ` Marcelo Tosatti
2012-11-23 1:16 ` [PATCH 0/3] " Marcelo Tosatti
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=20121127233246.GB8295@amt.cnet \
--to=mtosatti@redhat.com \
--cc=avi@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=xiaoguangrong@linux.vnet.ibm.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®