From: Andi Kleen <ak@linux.intel.com>
To: Jim Mattson <jmattson@google.com>
Cc: "Wanpeng Li" <kernellwp@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
"kvm list" <kvm@vger.kernel.org>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Wanpeng Li" <wanpeng.li@hotmail.com>
Subject: Re: [PATCH] KVM: VMX: Cache IA32_DEBUGCTL in memory
Date: Wed, 29 Nov 2017 12:56:24 -0800 [thread overview]
Message-ID: <20171129205624.GD3070@tassilo.jf.intel.com> (raw)
In-Reply-To: <CALMp9eSmqa8Wgvcwa=58CvBndfKQ6N_Uf8HTpMPe8WC_gM-iGA@mail.gmail.com>
On Wed, Nov 29, 2017 at 11:05:46AM -0800, Jim Mattson wrote:
> An alternative is to give the L1 guest read permission for this MSR in
> the MSR permission bitmaps. It's still going to be ~80 cycles, but
> that's better than the cost of a VM-exit/VM-entry round-trip.
It's a useful optimization, 80 cycles is 80 cycles.
The cache invalidation could likely be really simple, like:
have a global counter
always check the counter before and after and don't use the cache
if they don't match.
change KDB etc. to increase the counter.
-Andi
next prev parent reply other threads:[~2017-11-29 20:56 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-29 6:07 [PATCH] KVM: VMX: Cache IA32_DEBUGCTL in memory Wanpeng Li
2017-11-29 8:48 ` Paolo Bonzini
2017-11-29 8:51 ` Wanpeng Li
2017-11-29 9:13 ` Paolo Bonzini
2017-11-29 9:20 ` Wanpeng Li
2017-11-29 18:20 ` Andi Kleen
2017-11-29 19:05 ` Jim Mattson
2017-11-29 20:56 ` Andi Kleen [this message]
2017-11-29 22:26 ` Paolo Bonzini
2017-11-29 22:45 ` Andi Kleen
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=20171129205624.GD3070@tassilo.jf.intel.com \
--to=ak@linux.intel.com \
--cc=jmattson@google.com \
--cc=kernellwp@gmail.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=rkrcmar@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