From: peterz@infradead.org
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>, Kyle Huey <me@kylehuey.com>,
Thomas Gleixner <tglx@linutronix.de>,
Alexandre Chartre <alexandre.chartre@oracle.com>,
Robert O'Callahan <rocallahan@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>, "Paul E. McKenney" <paulmck@kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Petr Mladek <pmladek@suse.com>,
Steven Rostedt <rostedt@goodmis.org>,
Joel Fernandes <joel@joelfernandes.org>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Juergen Gross <jgross@suse.com>, Brian Gerst <brgerst@gmail.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Will Deacon <will@kernel.org>
Subject: Re: [REGRESSION 5.8] x86/entry: DR0 break-on-write not working
Date: Thu, 20 Aug 2020 10:35:39 +0200 [thread overview]
Message-ID: <20200820083539.GN2674@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200820034636.tl4nq5aiitpfvx62@treble>
On Wed, Aug 19, 2020 at 10:46:36PM -0500, Josh Poimboeuf wrote:
> On Wed, Aug 19, 2020 at 05:14:18PM -0700, Andy Lutomirski wrote:
> > I'm pretty sure you have the buggy sequence of events right, but for
> > the wrong reason. There's nothing wrong with scheduling when
> > delivering SIGTRAP, but it's definitely wrong to blindly save and
> > restore DR7 around scheduling and around ptrace invocations. Remember
> > this is an entry from user mode, so it runs on the user stack.
*groan*, yeah that's broken :/
> Wow, I had no idea user #DB's run on the task stack. The scheduling
> from #DB blew my mind :-) What's the purpose of that?
At the very least that vm86 junk needs to I think. Also -RT needs it to
send signals.
prev parent reply other threads:[~2020-08-20 8:36 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-19 17:53 Kyle Huey
2020-08-19 18:41 ` peterz
2020-08-19 19:28 ` Kyle Huey
2020-08-19 21:35 ` Peter Zijlstra
2020-08-19 22:47 ` Josh Poimboeuf
2020-08-20 0:14 ` Andy Lutomirski
2020-08-20 3:46 ` Josh Poimboeuf
2020-08-20 8:35 ` peterz [this message]
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