From 1eb3fc0a0b61b5d22adee2a9add3162a6c03a47e Mon Sep 17 00:00:00 2001 From: "Dr. David Alan Gilbert" Date: Wed, 17 May 2017 17:58:09 +0100 Subject: [PATCH] migration: Fix non-multiple of page size migration 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 Red Hat bug: https://bugzilla.redhat.com/show_bug.cgi?id=1449037 Signed-off-by: Dr. David Alan Gilbert Reviewed-by: Juan Quintela Signed-off-by: Juan Quintela --- migration/ram.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/migration/ram.c b/migration/ram.c index f59fdd41a4..59459efe18 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -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--;