From: Avi Kivity <avi@qumranet.com>
Date: Tue, 23 Jan 2007 04:40:40 +0000 (-0800)
Subject: [PATCH] KVM: fix bogus pagefault on writable pages
X-Git-Tag: v2.6.20-rc6~37
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fc3dffe12148b9612870eb21b24f2aecefa9ea24;p=pandora-kernel.git

[PATCH] KVM: fix bogus pagefault on writable pages

If a page is marked as dirty in the guest pte, set_pte_common() can set the
writable bit on newly-instantiated shadow pte.  This optimization avoids
a write fault after the initial read fault.

However, if a write fault instantiates the pte, fix_write_pf() incorrectly
reports the fault as a guest page fault, and the guest oopses on what appears
to be a correctly-mapped page.

Fix is to detect the condition and only report a guest page fault on a user
access to a kernel page.

With the fix, a kvm guest can survive a whole night of running the kernel
hacker's screensaver (make -j9 in a loop).

Signed-off-by: Avi Kivity <avi@qumranet.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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