linux-kernel - Re: [PATCH v2 1/3] x86/entry/64: Refactor IRQ stacks and make them NMI-safe

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Date:	Mon, 17 Aug 2015 14:18:27 +0300
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Andy Lutomirski <luto@...nel.org>
Cc:	X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Brian Gerst <brgerst@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>, Willy Tarreau <w@....eu>,
	Borislav Petkov <bp@...en8.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v2 1/3] x86/entry/64: Refactor IRQ stacks and make them NMI-safe

On Sat, Jul 25, 2015 at 8:57 AM, Andy Lutomirski <luto@...nel.org> wrote:
> This will allow IRQ stacks to nest inside NMIs or similar entries
> that can happen during IRQ stack setup or teardown.
>
> The Xen code here has a confusing comment.
>
> The new macros won't work correctly if they're invoked with IRQs on.
> Add a check under CONFIG_DEBUG_ENTRY to detect that.
>

> +/*
> + * Enters the IRQ stack if we're not already using it.  NMI-safe.  Clobbers
> + * flags and puts old RSP into old_rsp, and leaves all other GPRs alone.
> + * Requires kernel GSBASE.
> + *
> + * The invariant is that, if irq_count != 1, then the IRQ stack is in use.
> + */

I might be wrong, but shouldn't be this read as 'if irq_count != -1' ?

-- 
With Best Regards,
Andy Shevchenko
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