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migration: Fix non-multiple of page size migration

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Unfortunately it's legal to create a VM with a RAM size that's
not a multiple of the underlying host page or huge page size.
Recently I'd changed things to always send host sized pages,
and that breaks if we have say a 1025MB guest on 2MB hugepages.

Unfortunately we can't just make that illegal since it would break
migration from/to existing oddly configured VMs.

Symptom: qemu-system-x86_64: Illegal RAM offset 40100000
     as it transmits the fraction of the hugepage after the end
     of the RAMBlock (may also cause a crash on the source
     - possibly due to clearing bits after the bitmap)

Reported-by:  Yumei Huang <yuhuang@redhat.com>
Red Hat bug: https://bugzilla.redhat.com/show_bug.cgi?id=1449037

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Dr. David Alan Gilbert 2017-05-17 17:58:09 +01:00 committed by Juan Quintela
parent 56821559f0
commit 1eb3fc0a0b
1 changed files with 4 additions and 1 deletions
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5
migration/ram.c
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@ -1312,6 +1312,8 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss,
* a host page in which case the remainder of the hostpage is sent.
* Only dirty target pages are sent. Note that the host page size may
* be a huge page for this block.
* The saving stops at the boundary of the used_length of the block
* if the RAMBlock isn't a multiple of the host page size.
*
* Returns the number of pages written or negative on error
*
@ -1335,7 +1337,8 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,
pages += tmppages;
pss->page++;
} while (pss->page & (pagesize_bits - 1));
} while ((pss->page & (pagesize_bits - 1)) &&
offset_in_ramblock(pss->block, pss->page << TARGET_PAGE_BITS));
/* The offset we leave with is the last one we looked at */
pss->page--;