Messages in this thread Patch in this message | | | Subject | [PATCH 5/5] KVM: Fix bogus pagefault on writable pages | From | Avi Kivity <> | Date | Thu, 11 Jan 2007 10:07:30 -0000 |
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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>
Index: linux-2.6/drivers/kvm/paging_tmpl.h =================================================================== --- linux-2.6.orig/drivers/kvm/paging_tmpl.h +++ linux-2.6/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) { - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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