On Thu, Oct 15, 2020 at 10:00:15AM +0200, David Hildenbrand wrote: >On 15.10.20 06:02, Wei Yang wrote: >> On Mon, Oct 12, 2020 at 02:52:56PM +0200, David Hildenbrand wrote: >>> We actually need one byte less (next_mb_id is exclusive, first_mb_id is >>> inclusive). Simplify. >>> >>> Cc: "Michael S. Tsirkin" <[email protected]> >>> Cc: Jason Wang <[email protected]> >>> Cc: Pankaj Gupta <[email protected]> >>> Signed-off-by: David Hildenbrand <[email protected]> >>> --- >>> drivers/virtio/virtio_mem.c | 4 ++-- >>> 1 file changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c >>> index a1f5bf7a571a..670b3faf412d 100644 >>> --- a/drivers/virtio/virtio_mem.c >>> +++ b/drivers/virtio/virtio_mem.c >>> @@ -257,8 +257,8 @@ static enum virtio_mem_mb_state >>> virtio_mem_mb_get_state(struct virtio_mem *vm, >>> */ >>> static int virtio_mem_mb_state_prepare_next_mb(struct virtio_mem *vm) >>> { >>> - unsigned long old_bytes = vm->next_mb_id - vm->first_mb_id + 1; >>> - unsigned long new_bytes = vm->next_mb_id - vm->first_mb_id + 2; >>> + unsigned long old_bytes = vm->next_mb_id - vm->first_mb_id; >>> + unsigned long new_bytes = old_bytes + 1; >> >> This is correct. >> >> So this looks more like a fix? > >We allocate an additional new page "one memory block too early". > >So we would allocate the first page for blocks 0..510, and already >allocate the second page with block 511, although we could have fit it >into the first page. Block 512 will then find that the second page is >already there and simply use the second page. > >So as we do it consistently, nothing will go wrong - that's why I >avoided using the "fix" terminology. >
Yes, my feeling is this is not a simplification. Instead this is a more precise calculation. How about use this subject? virtio-mem: more precise calculation in virtio_mem_mb_state_prepare_next_mb() >Thanks! > >-- >Thanks, > >David / dhildenb -- Wei Yang Help you, Help me
