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由 David Vrabel 提交于
This reverts commit a9c8e4be. PTEs in Xen PV guests must contain machine addresses if _PAGE_PRESENT is set and pseudo-physical addresses is _PAGE_PRESENT is clear. This is because during a domain save/restore (migration) the page table entries are "canonicalised" and uncanonicalised". i.e., MFNs are converted to PFNs during domain save so that on a restore the page table entries may be rewritten with the new MFNs on the destination. This canonicalisation is only done for PTEs that are present. This change resulted in writing PTEs with MFNs if _PAGE_PROTNONE (or _PAGE_NUMA) was set but _PAGE_PRESENT was clear. These PTEs would be migrated as-is which would result in unexpected behaviour in the destination domain. Either a) the MFN would be translated to the wrong PFN/page; b) setting the _PAGE_PRESENT bit would clear the PTE because the MFN is no longer owned by the domain; or c) the present bit would not get set. Symptoms include "Bad page" reports when munmapping after migrating a domain. Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com> Acked-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: <stable@vger.kernel.org> [3.12+]
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