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[Qemu-devel] [RFC/BUG] xen-mapcache: buggy invalidate map cache?

From: hrg
Subject: [Qemu-devel] [RFC/BUG] xen-mapcache: buggy invalidate map cache?
Date: Sun, 9 Apr 2017 23:52:34 +0800


In xen_map_cache_unlocked(), map to guest memory maybe in entry->next
instead of first level entry (if map to rom other than guest memory
comes first), while in xen_invalidate_map_cache(), when VM ballooned
out memory, qemu did not invalidate cache entries in linked
list(entry->next), so when VM balloon back in memory, gfns probably
mapped to different mfns, thus if guest asks device to DMA to these
GPA, qemu may DMA to stale MFNs.

So I think in xen_invalidate_map_cache() linked lists should also be
checked and invalidated.

What’s your opinion? Is this a bug? Is my analyze correct?

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