From: "Dr. David Alan Gilbert"
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 4010
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
Red Hat bug: https://bugzilla.redhat.com/show_bug.cgi?id=1449037
Signed-off-by: Dr. David Alan Gilbert
---
migration/ram.c | 5 -
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/migration/ram.c b/migration/ram.c
index 293d27ce83..cea8924c02 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1305,6 +1305,8 @@ 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
*
@@ -1328,7 +1330,8 @@ 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--;
--
2.13.0
