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From: Peter Zijlstra <peterz@infradead.org>
To: Andy Lutomirski <luto@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	Juergen Gross <jgross@suse.com>,
	LKML <linux-kernel@vger.kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>,
	Joel Fernandes <joel@joelfernandes.org>,
	He Zhe <zhe.he@windriver.com>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [RFC][PATCH] tracing/x86: Save CR2 before tracing irqsoff on error_entry
Date: Thu, 21 Mar 2019 19:33:28 +0100	[thread overview]
Message-ID: <20190321183327.GW5996@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CALCETrVd8i9xmGT9GPXU6tuvte+M9e3otYa8YNLEgPE+W81E2w@mail.gmail.com>

On Thu, Mar 21, 2019 at 11:28:50AM -0700, Andy Lutomirski wrote:
> On Thu, Mar 21, 2019 at 11:27 AM Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > On Thu, Mar 21, 2019 at 11:05:06AM -0700, Andy Lutomirski wrote:
> >
> > > Ugh.
> > >
> > > I certainly agree in principle that sticking the CR2 read into the asm
> > > is the right solution.  But this patch makes the spaghetti even more
> > > tangled.  Maybe we can rearrange the code a bit so that the entry
> > > sequence saves at least one register before calling error_entry, so we
> > > can do it the obvious way.
> >
> > What is the obvious way? Note that with all the Xen/paravirt-me-harder
> > bits on, we need to clobber at least RAX to get CR2.
> >
> > And most of the patch was munging the paravirt bits to make that happen.
> >
> > Another thing I did notices is that CLAC and CLD are not next to one
> > another in these paths.
> 
> The thing I really don't like is all the EBX crud to try to get
> everything in to the right order.

Ah yes, granted. I hate that part too but didn't see a way around it :/

  reply	other threads:[~2019-03-21 18:33 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-21  2:15 [RFC][PATCH] tracing/x86: Save CR2 before tracing irqsoff on error_entry Steven Rostedt
2019-03-21  8:33 ` Peter Zijlstra
2019-03-21  9:02   ` Peter Zijlstra
2019-03-21 10:45     ` Peter Zijlstra
2019-03-21 13:32       ` Steven Rostedt
2019-03-21 13:55         ` Steven Rostedt
2019-03-21 17:23           ` Linus Torvalds
2019-03-21 17:22         ` Peter Zijlstra
2019-03-21 18:05           ` Andy Lutomirski
2019-03-21 18:10             ` Steven Rostedt
2019-03-21 18:27               ` Andy Lutomirski
2019-03-21 20:50                 ` Peter Zijlstra
2019-03-22  2:52                   ` Andy Lutomirski
2019-03-21 18:28               ` Peter Zijlstra
2019-03-21 18:55                 ` Steven Rostedt
2019-03-21 19:31                   ` Peter Zijlstra
2019-03-21 19:50                     ` Steven Rostedt
2019-03-21 20:03                       ` Peter Zijlstra
2019-03-21 20:11                         ` Steven Rostedt
2019-03-21 18:18             ` Linus Torvalds
2019-03-21 18:20               ` Andy Lutomirski
2019-03-21 18:25                 ` Linus Torvalds
2019-03-21 18:37                   ` Peter Zijlstra
2019-03-21 18:39                     ` Andy Lutomirski
2019-03-21 20:00                       ` Andrew Cooper
2019-03-21 20:35                         ` Steven Rostedt
2019-03-21 18:38                   ` Andy Lutomirski
2019-03-21 18:42                     ` Peter Zijlstra
2019-03-21 18:22               ` hpa
2019-03-22  5:54               ` Juergen Gross
2019-03-21 18:27             ` Peter Zijlstra
2019-03-21 18:28               ` Andy Lutomirski
2019-03-21 18:33                 ` Peter Zijlstra [this message]
2019-03-21 13:04   ` Steven Rostedt
2019-04-17  1:52 ` He Zhe

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