> -----Original Message-----
> From: Roger Pau Monne [mailto:roger....@citrix.com]
> Sent: 18 March 2019 15:46
> To: qemu-devel@nongnu.org
> Cc: Roger Pau Monne <roger....@citrix.com>; Stefano Stabellini
> <sstabell...@kernel.org>; Anthony
> Perard <anthony.per...@citrix.com>; Paul Durrant <paul.durr...@citrix.com>;
> Igor Druzhinin
> <igor.druzhi...@citrix.com>; Paolo Bonzini <pbonz...@redhat.com>; Richard
> Henderson <r...@twiddle.net>;
> Eduardo Habkost <ehabk...@redhat.com>; Michael S. Tsirkin <m...@redhat.com>;
> Marcel Apfelbaum
> <marcel.apfelb...@gmail.com>; xen-de...@lists.xenproject.org
> Subject: [PATCH v2] xen-mapcache: use MAP_FIXED flag so the mmap address hint
> is always honored
>
> 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 <roger....@citrix.com>
Reviewed-by: Paul Durrant <paul.durr...@citrix.com>
> ---
> Cc: Stefano Stabellini <sstabell...@kernel.org>
> Cc: Anthony Perard <anthony.per...@citrix.com>
> Cc: Paul Durrant <paul.durr...@citrix.com>
> Cc: Igor Druzhinin <igor.druzhi...@citrix.com>
> Cc: Paolo Bonzini <pbonz...@redhat.com>
> Cc: Richard Henderson <r...@twiddle.net>
> Cc: Eduardo Habkost <ehabk...@redhat.com>
> Cc: "Michael S. Tsirkin" <m...@redhat.com>
> Cc: Marcel Apfelbaum <marcel.apfelb...@gmail.com>
> Cc: xen-de...@lists.xenproject.org
> ---
> Changes since v1:
> - Use MAP_FIXED for the dummy mmap call also if a specific virtual
> address is requested.
> ---
> 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..23de5517db 100644
> --- a/hw/i386/xen/xen-mapcache.c
> +++ b/hw/i386/xen/xen-mapcache.c
> @@ -185,8 +185,13 @@ static void xen_remap_bucket(MapCacheEntry *entry,
> }
>
> if (!dummy) {
> + /*
> + * If the caller has requested the mapping at a specific address use
> + * MAP_FIXED to make sure it's honored.
> + */
> 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);
> --
> 2.17.2 (Apple Git-113)
