From: Jan Beulich <jbeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: "Roger Pau Monné" <roger.pau@citrix.com>, "Wei Liu" <wl@xen.org>,
Xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH 1/5] x86/xstate: Elide redundant writes in set_xcr0()
Date: Tue, 4 May 2021 13:51:36 +0200 [thread overview]
Message-ID: <39d641e7-107b-0e60-8fc2-6f6c2303f072@suse.com> (raw)
In-Reply-To: <20210503153938.14109-2-andrew.cooper3@citrix.com>
On 03.05.2021 17:39, Andrew Cooper wrote:
> XSETBV is an expensive instruction as, amongst other things, it involves
> reconfiguring the instruction decode at the frontend of the pipeline.
>
> We have several paths which reconfigure %xcr0 in quick succession (the context
> switch path has 5, including the fpu save/restore helpers), and only a single
> caller takes any care to try to skip redundant writes.
>
> Update set_xcr0() to perform amortisation automatically, and simplify the
> __context_switch() path as a consequence.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
next prev parent reply other threads:[~2021-05-04 11:51 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-03 15:39 [PATCH 0/5] x86/xstate: Fixes to size calculations Andrew Cooper
2021-05-03 15:39 ` [PATCH 1/5] x86/xstate: Elide redundant writes in set_xcr0() Andrew Cooper
2021-05-04 11:51 ` Jan Beulich [this message]
2021-05-03 15:39 ` [PATCH 2/5] x86/xstate: Rename _xstate_ctxt_size() to hw_uncompressed_size() Andrew Cooper
2021-05-04 11:53 ` Jan Beulich
2021-05-03 15:39 ` [PATCH 3/5] x86/xstate: Rework xstate_ctxt_size() as xstate_uncompressed_size() Andrew Cooper
2021-05-03 18:17 ` Andrew Cooper
2021-05-04 12:08 ` Jan Beulich
2021-05-04 12:15 ` Andrew Cooper
2021-05-04 12:20 ` Jan Beulich
2021-05-04 12:22 ` Andrew Cooper
2021-05-04 12:45 ` Jan Beulich
2021-05-03 15:39 ` [PATCH 4/5] x86/cpuid: Simplify recalculate_xstate() Andrew Cooper
2021-05-04 12:43 ` Jan Beulich
2021-05-04 13:58 ` Andrew Cooper
2021-05-05 8:19 ` Jan Beulich
2021-05-05 14:53 ` Andrew Cooper
2021-05-05 15:14 ` Jan Beulich
2021-05-03 15:39 ` [PATCH 5/5] x86/cpuid: Fix handling of xsave dynamic leaves Andrew Cooper
2021-05-04 12:56 ` Jan Beulich
2021-05-04 14:17 ` Andrew Cooper
2021-05-05 8:33 ` Jan Beulich
2021-05-05 16:59 ` Andrew Cooper
2021-05-06 6:17 ` Jan Beulich
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=39d641e7-107b-0e60-8fc2-6f6c2303f072@suse.com \
--to=jbeulich@suse.com \
--cc=andrew.cooper3@citrix.com \
--cc=roger.pau@citrix.com \
--cc=wl@xen.org \
--cc=xen-devel@lists.xenproject.org \
/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;
as well as URLs for NNTP newsgroup(s).