[Xen-devel] Re: [PATCH] fix pgd_lock deadlock

To:	Jan Beulich <JBeulich@xxxxxxxxxx>
Subject:	[Xen-devel] Re: [PATCH] fix pgd_lock deadlock
From:	Andrea Arcangeli <aarcange@xxxxxxxxxx>
Date:	Tue, 22 Feb 2011 14:49:56 +0100
Cc:	Jeremy Fitzhardinge <jeremy@xxxxxxxx>, "Xen-devel@xxxxxxxxxxxxxxxxxxx" <Xen-devel@xxxxxxxxxxxxxxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, the arch/x86 maintainers <x86@xxxxxxxxxx>, Hugh Dickins <hughd@xxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Larry Woodman <lwoodman@xxxxxxxxxx>, Andi Kleen <andi@xxxxxxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Johannes Weiner <jweiner@xxxxxxxxxx>
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On Tue, Feb 22, 2011 at 07:48:54AM +0000, Jan Beulich wrote:
> A possible alternative would be to acquire the page table lock
> in vmalloc_sync_all() only in the Xen case (perhaps by storing
> NULL into page->index in pgd_set_mm() when not running on
> Xen). This is utilizing the fact that there aren't (supposed to
> be - for non-pvops this is definitely the case) any TLB flush IPIs
> under Xen, and hence the race you're trying to fix doesn't
> exist there (while non-Xen doesn't need the extra locking).

That's sure ok with me. Can we use a global runtime to check if the
guest is running under Xen paravirt, instead of passing that info
through page->something?

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[Xen-devel] Re: [PATCH] fix pgd_lock deadlock