From: Peter Zijlstra <peterz@infradead.org>
To: "Lendacky, Thomas" <Thomas.Lendacky@amd.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"x86@kernel.org" <x86@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Namhyung Kim <namhyung@kernel.org>, Jiri Olsa <jolsa@redhat.com>,
Jerry Hoemann <jerry.hoemann@hpe.com>
Subject: Re: [PATCH] perf/x86/amd: Change NMI latency mitigation to use a timestamp
Date: Fri, 2 Aug 2019 18:33:28 +0200 [thread overview]
Message-ID: <20190802163328.GB2349@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190802162015.GA2349@hirez.programming.kicks-ass.net>
On Fri, Aug 02, 2019 at 06:20:15PM +0200, Peter Zijlstra wrote:
> On Fri, Aug 02, 2019 at 02:33:41PM +0000, Lendacky, Thomas wrote:
> > Talking to the hardware folks, they say setting CR8 is a serializing
> > instruction and has to communicate out to the APIC, so it's better to
> > use CLI/STI.
>
> Bah; the Intel SDM states: "MOV CR* instructions, except for MOV CR8,
> are serializing instructions", which had given me a little hope.
>
> At the same time, all these chips still have the APIC TPR field too, so
> much like how the TSC DEADLINE MSR is a hidden APIC write, so too is CR8
> I suppose :-(
>
> I'll still finish the patches I started, just to see what it would look
> like.
Another 'fun' issue I ran into while doing these patches; STI has a 1
instruction shadow, which we rely on, MOV CR8 does not. So things like:
native_safe_halt:
sti
hlt
turn into:
native_safe_halt:
cli
movl $0, %rax
movq %rax, %cr8
sti
hlt
next prev parent reply other threads:[~2019-08-02 16:33 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-01 18:57 [PATCH] perf/x86/amd: Change NMI latency mitigation to use a timestamp Lendacky, Thomas
2019-08-01 21:16 ` Peter Zijlstra
2019-08-01 21:29 ` Lendacky, Thomas
2019-08-01 21:34 ` Thomas Gleixner
2019-08-01 21:48 ` Peter Zijlstra
2019-08-01 21:59 ` Thomas Gleixner
2019-08-02 14:33 ` Lendacky, Thomas
2019-08-02 16:20 ` Peter Zijlstra
2019-08-02 16:33 ` Peter Zijlstra [this message]
2019-08-08 20:33 ` Jerry Hoemann
2019-09-13 19:52 ` Jerry Hoemann
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=20190802163328.GB2349@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=Thomas.Lendacky@amd.com \
--cc=acme@kernel.org \
--cc=alexander.shishkin@linux.intel.com \
--cc=bp@alien8.de \
--cc=jerry.hoemann@hpe.com \
--cc=jolsa@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=namhyung@kernel.org \
--cc=tglx@linutronix.de \
--cc=x86@kernel.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).