From: Borislav Petkov <bp@alien8.de>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Brian Gerst <brgerst@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>, Willy Tarreau <w@1wt.eu>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 1/3] x86/entry/64: Refactor IRQ stacks and make then NMI-safe
Date: Fri, 24 Jul 2015 12:25:03 +0200 [thread overview]
Message-ID: <20150724102503.GA19090@nazgul.tnic> (raw)
In-Reply-To: <CALCETrUtaTGA0uq5t_VbbPB-VwOp_vswdUjenZZOS0JNdKMqCA@mail.gmail.com>
On Thu, Jul 23, 2015 at 11:08:39PM -0700, Andy Lutomirski wrote:
> To be obviously safe against any local exception, we want a single
> instruction that will change %rsp and some in-memory flag at the same
> time. There aren't a whole lot of candidates. Cmpxchg isn't useful
> (cmpxchg with a memory operand doesn't modify its register operand).
Why would you even need that?
You do LOCK; CMPXCHG on a per_cpu variable and then test ZF? I.e., use
it as a mutex in asm. With ZF=1, you switch stacks, with ZF=0, you
busy-wait ...
Or am I missing something?
This way you serialize all irq stack switchers...
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
--
next prev parent reply other threads:[~2015-07-24 10:25 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-23 22:37 [PATCH 0/3] x86_64: Make int3 non-magical Andy Lutomirski
2015-07-23 22:37 ` [PATCH 1/3] x86/entry/64: Refactor IRQ stacks and make then NMI-safe Andy Lutomirski
2015-07-24 6:08 ` Andy Lutomirski
2015-07-24 10:25 ` Borislav Petkov [this message]
2015-07-24 18:02 ` Andy Lutomirski
2015-07-25 4:16 ` Borislav Petkov
2015-07-25 4:28 ` Andy Lutomirski
2015-07-25 4:32 ` Borislav Petkov
2015-07-25 4:59 ` Andy Lutomirski
2015-07-25 8:39 ` Borislav Petkov
2015-07-25 17:56 ` Linus Torvalds
2015-07-25 17:59 ` Andy Lutomirski
2015-07-25 18:12 ` Linus Torvalds
2015-08-05 8:59 ` Ingo Molnar
2015-08-05 18:24 ` Andy Lutomirski
2015-08-05 18:27 ` Steven Rostedt
2015-08-05 18:32 ` Andy Lutomirski
2015-08-22 13:55 ` Ingo Molnar
2015-07-23 22:37 ` [PATCH 2/3] x86/entry/64: Teach idtentry to use the IRQ stack Andy Lutomirski
2015-07-23 22:37 ` [PATCH 3/3] x86/entry/64: Move #BP from IST to " Andy Lutomirski
2015-07-24 11:02 ` Borislav Petkov
2015-07-23 22:39 ` [PATCH 0/3] x86_64: Make int3 non-magical Andy Lutomirski
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