Red Hat Bugzilla – Bug 249813
Kernel triggers thousands of PTWR fixups on pte_clear()
Last modified: 2007-11-16 20:14:56 EST
pte_clear() is defined in 2.6.9-55.EL as set_pte(...,0). This clears the upper
word before the lower word which means for MFN>4G the PTE value is temporarily
invalid as far as Xen's page type tracking is concerned because the P bit is set
when the top bits are cleared:
(XEN) mm.c:649:d25 Error getting mfn 1f20e (pfn 5555555555555555) from L1 entry
000000001f20e063 for dom25
(XEN) mm.c:3295:d25 ptwr_emulate: fixing up invalid PAE PTE 000000001f20e063
(XEN) printk: 4246 messages suppressed.
The fix is to define pte_clear to clear the lower word first
Thanks for pointing out these bugs, Ian.
This particular one already had a patch submitted internally on May 30th 2007, I
assume that one is already in our tree.
Chris, can this patch go into MODIFIED?
Yeah, this has now been committed to our internal CVS, so MODIFIED it is.
Thanks for the bug report, Ian.
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