linux-kernel - [PATCH] Fix lazy mode vmalloc synchronization for paravirt

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Message-ID: <46CB91BC.2010808@vmware.com>
Date:	Tue, 21 Aug 2007 18:30:36 -0700
From:	Zachary Amsden <zach@...are.com>
To:	Virtualization Mailing List <virtualization@...ts.osdl.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...l.org>,
	Chris Wright <chrisw@...s-sol.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Jeremy Fitzhardinge <jeremy@...p.org>, Andi Kleen <ak@...e.de>,
	Andrew Morton <akpm@...l.org>
CC:	Ben Collins <ben.collins@...ntu.com>
Subject: [PATCH] Fix lazy mode vmalloc synchronization for paravirt

Found this looping Ubuntu installs with VMI.

If unlucky enough to hit a vmalloc sync fault during a lazy mode 
operation (from an IRQ handler for a module which was not yet populated 
in current page directory, or from inside copy_one_pte, which touches 
swap_map, and hit in an unused 4M region), the required PDE update would 
never get flushed, causing an infinite page fault loop.

This bug affects any paravirt-ops backend which uses lazy updates, I 
believe that makes it a bug in Xen, VMI and lguest.  It only happens on 
LOWMEM kernels.

Currently for 2.6.23, but we'll want to backport to -stable as well.

Zach

View attachment "i386-linus-vmalloc-paravirt-fix.patch" of type "text/x-patch" (824 bytes)