From: Andi Kleen <andi@firstfloor.org>
To: Keno Fischer <keno@juliacomputing.com>
Cc: "Andi Kleen" <andi@firstfloor.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
"Borislav Petkov" <bp@suse.de>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Kyle Huey" <khuey@kylehuey.com>,
"Robert O'Callahan" <robert@ocallahan.org>
Subject: Re: [RFC PATCH] x86/arch_prctl: Add ARCH_SET_XCR0 to mask XCR0 per-thread
Date: Mon, 18 Jun 2018 09:58:40 -0700 [thread overview]
Message-ID: <20180618165840.gikljqhaxtiiw27x@two.firstfloor.org> (raw)
In-Reply-To: <CABV8kRyf2R=a2zezgovByK9Lc8HhDXyfZ4OPE_DHfKKg34bNfw@mail.gmail.com>
> Unfortunately, that is insufficient. Almost difference in CPU behavior
> between the replayer
> and the replayee. In particular, the problems for rr here are
> 1) xgetbv, which can introduce differing register contents (and if
> code branches on this,
> potentially differences in control flow).
So you're saying that software checks XGETBV first before checking
CPUID?
That seems broken. Without AVX XGETBV may not exist.
You always have to check CPUID first. And then it should just branch
around the XGETBV.
So we're talking about a workaround for broken software. The question
is how wide spread is it?
> 2) xsave writing more memory than the trace expects, causing
> divergence in the memory
> contents of the process.
Do memory contents which are never read by the application matter?
-Andi
next prev parent reply other threads:[~2018-06-18 16:58 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-17 0:33 [RFC PATCH] x86/arch_prctl: Add ARCH_SET_XCR0 to mask XCR0 per-thread Keno Fischer
2018-06-17 16:35 ` Andi Kleen
2018-06-17 16:48 ` Keno Fischer
2018-06-17 18:22 ` Keno Fischer
2018-06-18 16:58 ` Andi Kleen [this message]
2018-06-18 17:50 ` Keno Fischer
2018-06-19 13:43 ` Andi Kleen
2018-06-18 12:47 ` Dave Hansen
2018-06-18 14:42 ` Keno Fischer
2018-06-18 15:04 ` Dave Hansen
2018-06-18 15:13 ` Keno Fischer
2018-06-18 16:16 ` Dave Hansen
2018-06-18 17:22 ` Keno Fischer
2018-06-18 17:29 ` Dave Hansen
2018-06-18 17:43 ` Dave Hansen
2018-06-18 18:16 ` Keno Fischer
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=20180618165840.gikljqhaxtiiw27x@two.firstfloor.org \
--to=andi@firstfloor.org \
--cc=bp@suse.de \
--cc=dave.hansen@linux.intel.com \
--cc=hpa@zytor.com \
--cc=keno@juliacomputing.com \
--cc=khuey@kylehuey.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=pbonzini@redhat.com \
--cc=rkrcmar@redhat.com \
--cc=robert@ocallahan.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).