From 4158e93f4aced247c8db94a0275fc027da7dc97e Mon Sep 17 00:00:00 2001 From: Roger Pau Monne Date: Mon, 18 Mar 2019 18:37:31 +0100 Subject: [PATCH] xen-mapcache: use MAP_FIXED flag so the mmap address hint is always honored MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Or if it's not possible to honor the hinted address an error is returned instead. This makes it easier to spot the actual failure, instead of failing later on when the caller of xen_remap_bucket realizes the mapping has not been created at the requested address. Also note that at least on FreeBSD using MAP_FIXED will cause mmap to try harder to honor the passed address. Signed-off-by: Roger Pau Monné Reviewed-by: Paul Durrant Acked-by: Anthony PERARD Reviewed-by: Igor Druzhinin Message-Id: <20190318173731.14494-1-roger.pau@citrix.com> Signed-off-by: Anthony PERARD --- hw/i386/xen/xen-mapcache.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/hw/i386/xen/xen-mapcache.c b/hw/i386/xen/xen-mapcache.c index 349f72d00c..254759f776 100644 --- a/hw/i386/xen/xen-mapcache.c +++ b/hw/i386/xen/xen-mapcache.c @@ -184,9 +184,14 @@ static void xen_remap_bucket(MapCacheEntry *entry, pfns[i] = (address_index << (MCACHE_BUCKET_SHIFT-XC_PAGE_SHIFT)) + i; } + /* + * If the caller has requested the mapping at a specific address use + * MAP_FIXED to make sure it's honored. + */ if (!dummy) { vaddr_base = xenforeignmemory_map2(xen_fmem, xen_domid, vaddr, - PROT_READ | PROT_WRITE, 0, + PROT_READ | PROT_WRITE, + vaddr ? MAP_FIXED : 0, nb_pfn, pfns, err); if (vaddr_base == NULL) { perror("xenforeignmemory_map2"); @@ -198,7 +203,8 @@ static void xen_remap_bucket(MapCacheEntry *entry, * mapping immediately due to certain circumstances (i.e. on resume now) */ vaddr_base = mmap(vaddr, size, PROT_READ | PROT_WRITE, - MAP_ANON | MAP_SHARED, -1, 0); + MAP_ANON | MAP_SHARED | (vaddr ? MAP_FIXED : 0), + -1, 0); if (vaddr_base == MAP_FAILED) { perror("mmap"); exit(-1);