From 45e6cee42b98d10e2e14885ab656541a9ffd5187 Mon Sep 17 00:00:00 2001 From: David Gibson Date: Tue, 4 Dec 2012 11:38:39 +1100 Subject: [PATCH] migration: Fix madvise breakage if host and guest have different page sizes madvise(DONTNEED) will throw away the contents of the whole page at the given address, even if the given length is less than the page size. One can argue about whether that's the correct behaviour, but that's what it's done for a long time in Linux at least. That means that the madvise() in ram_load(), on a setup where TARGET_PAGE_SIZE is smaller than the host page size, can throw away data in guest pages adjacent to the one it's actually processing right now, leading to guest memory corruption on an incoming migration. This patch therefore, disables the madvise() if the host page size is larger than TARGET_PAGE_SIZE. This means we don't get the benefits of that madvise() in this case, but a more complete fix is more difficult to accomplish. This at least fixes the guest memory corruption. Signed-off-by: David Gibson Reported-by: Alexey Kardashevskiy Signed-off-by: Anthony Liguori --- arch_init.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch_init.c b/arch_init.c index b75a4c5580..83dcc53ff5 100644 --- a/arch_init.c +++ b/arch_init.c @@ -840,7 +840,8 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id) memset(host, ch, TARGET_PAGE_SIZE); #ifndef _WIN32 if (ch == 0 && - (!kvm_enabled() || kvm_has_sync_mmu())) { + (!kvm_enabled() || kvm_has_sync_mmu()) && + getpagesize() <= TARGET_PAGE_SIZE) { qemu_madvise(host, TARGET_PAGE_SIZE, QEMU_MADV_DONTNEED); } #endif -- 2.11.0