hostmem-file: add offset option

Add an option for hostmem-file to start the memory object at an offset
into the target file. This is useful if multiple memory objects reside
inside the same target file, such as a device node.

In particular, it's useful to map guest memory directly into /dev/mem
for experimentation.

To make this work consistently, also fix up all places in QEMU that
expect fd offsets to be 0.

Signed-off-by: Alexander Graf <graf@amazon.com>
Message-Id: <20230403221421.60877-1-graf@amazon.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
This commit is contained in:
Alexander Graf 2023-04-03 22:14:21 +00:00 committed by David Hildenbrand
parent 886c0453cb
commit 4b870dc4d0
9 changed files with 69 additions and 9 deletions

View file

@ -40,6 +40,7 @@ struct RAMBlock {
QLIST_ENTRY(RAMBlock) next;
QLIST_HEAD(, RAMBlockNotifier) ramblock_notifiers;
int fd;
uint64_t fd_offset;
size_t page_size;
/* dirty bitmap used during migration */
unsigned long *bmap;