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authorAvi Kivity <avi@qumranet.com>2007-01-22 20:40:40 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-01-23 07:52:06 -0800
commitfc3dffe12148b9612870eb21b24f2aecefa9ea24 (patch)
tree67a7671e73e5e962355885ffa7a25821c27247e7
parent038e51de2e7ae2c8e9d8a0b15231f8509875dc33 (diff)
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[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>
-rw-r--r--drivers/kvm/paging_tmpl.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/kvm/paging_tmpl.h b/drivers/kvm/paging_tmpl.h
index 2dbf4307ed9..6bc41950fbb 100644
--- a/drivers/kvm/paging_tmpl.h
+++ b/drivers/kvm/paging_tmpl.h
@@ -274,7 +274,7 @@ static int FNAME(fix_write_pf)(struct kvm_vcpu *vcpu,
struct kvm_mmu_page *page;
if (is_writeble_pte(*shadow_ent))
- return 0;
+ return !user || (*shadow_ent & PT_USER_MASK);
writable_shadow = *shadow_ent & PT_SHADOW_WRITABLE_MASK;
if (user) {