The patch titled
KVM: fix bogus pagefault on writable pages
has been added to the -mm tree. Its filename is
kvm-fix-bogus-pagefault-on-writable-pages.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: KVM: fix bogus pagefault on writable pages
From: Avi Kivity <avi@xxxxxxxxxxxx>
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@xxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
drivers/kvm/paging_tmpl.h | 2 +-
1 files changed, 1 insertion(+), 1 deletion(-)
diff -puN drivers/kvm/paging_tmpl.h~kvm-fix-bogus-pagefault-on-writable-pages drivers/kvm/paging_tmpl.h
--- a/drivers/kvm/paging_tmpl.h~kvm-fix-bogus-pagefault-on-writable-pages
+++ a/drivers/kvm/paging_tmpl.h
@@ -274,7 +274,7 @@ static int FNAME(fix_write_pf)(struct kv
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) {
_
Patches currently in -mm which might be from avi@xxxxxxxxxxxx are
kvm-add-vm-exit-profiling.patch
kvm-make-sure-there-is-a-vcpu-context-loaded-when.patch
kvm-fix-race-between-mmio-reads-and-injected-interrupts.patch
kvm-x86-emulator-fix-bit-string-instructions.patch
kvm-fix-asm-constraints-with-config_frame_pointer=n.patch
kvm-fix-bogus-pagefault-on-writable-pages.patch
-
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