On Fri, Jan 25, 2019 at 01:48:26PM +0100, Thomas Huth wrote: > On 2019-01-25 12:58, Liu, Changpeng wrote: > > > > > >> -----Original Message----- > >> From: Thomas Huth [mailto:th...@redhat.com] > >> Sent: Friday, January 25, 2019 4:49 PM > >> To: Stefano Garzarella <sgarz...@redhat.com>; Michael S. Tsirkin > >> <m...@redhat.com>; Liu, Changpeng <changpeng....@intel.com> > >> Cc: qemu-devel@nongnu.org; Laurent Vivier <lviv...@redhat.com>; Kevin Wolf > >> <kw...@redhat.com>; qemu-bl...@nongnu.org; Max Reitz > >> <mre...@redhat.com>; Stefan Hajnoczi <stefa...@redhat.com>; Paolo Bonzini > >> <pbonz...@redhat.com> > >> Subject: Re: [Qemu-devel] [PATCH RFC 2/2] tests/virtio-blk: add test for > >> WRITE_ZEROES command > >> > >> On 2019-01-25 09:16, Stefano Garzarella wrote: > >>> On Fri, Jan 25, 2019 at 07:07:35AM +0100, Thomas Huth wrote: > >>>> On 2019-01-25 07:01, Thomas Huth wrote: > >>>>> On 2019-01-24 18:23, Stefano Garzarella wrote: > >>>>>> If the WRITE_ZEROES feature is enabled, we check this > >>>>>> command in the test_basic(). > >>>>>> > >>>>>> Signed-off-by: Stefano Garzarella <sgarz...@redhat.com> > >>>>>> --- > >>>>>> tests/virtio-blk-test.c | 63 +++++++++++++++++++++++++++++++++++++++++ > >>>>>> 1 file changed, 63 insertions(+) > >>>>>> > >>>>>> diff --git a/tests/virtio-blk-test.c b/tests/virtio-blk-test.c > >>>>>> index 04c608764b..8cabbcb85a 100644 > >>>>>> --- a/tests/virtio-blk-test.c > >>>>>> +++ b/tests/virtio-blk-test.c > >>>>>> @@ -231,6 +231,69 @@ static void test_basic(QVirtioDevice *dev, > >> QGuestAllocator *alloc, > >>>>>> > >>>>>> guest_free(alloc, req_addr); > >>>>>> > >>>>>> + if (features & (1u << VIRTIO_BLK_F_WRITE_ZEROES)) { > >>>>>> + struct virtio_blk_discard_write_zeroes *dwz_hdr; > >>>>>> + void *expected; > >>>>>> + > >>>>>> + /* > >>>>>> + * WRITE_ZEROES request on the same sector of previous test > >>>>>> where > >>>>>> + * we wrote "TEST". > >>>>>> + */ > >>>>>> + req.type = VIRTIO_BLK_T_WRITE_ZEROES; > >>>>>> + req.data = g_malloc0(512); > >>>>> > >>>>> Wouldn't it be more interesting to do a memset(req.data, 0xaa, 512) or > >>>>> something similar here, to see whether zeroes or 0xaa is written? > >>>> > >>>> Ah, never mind, I thought req.data would be a sector buffer here, but > >>>> looking at the lines below, it apparently is something different. > >>>> > >>>> Why do you allocate 512 bytes here? I'd rather expect > >>>> g_malloc0(sizeof(struct virtio_blk_discard_write_zeroes)) here. ... and > >>>> then you could also use a local "struct virtio_blk_discard_write_zeroes > >>>> dwz_hdr" variable instead of a pointer, and drop the g_malloc0() > >>>> completely? > >>>> > >>> > >>> Hi Thomas, > >>> it was my initial implementation, but on the first test I discovered > >>> that virtio_blk_request() has an assert on the data_size and it requires > >>> a multiple of 512 bytes. > >>> Then I looked at the virtio-spec #1, and it seems that data should be > >>> multiple of 512 bytes also if it contains the struct > >>> virtio_blk_discard_write_zeroes. (I'm not sure) > >>> > >>> Anyway I tried to allocate only the space for that struct, commented the > >>> assert and the test works well. > >>> > >>> How do you suggest to proceed? > >> > >> Wow, that's a tough question. Looking at the virtio spec, I agree with > >> you, it looks like struct virtio_blk_discard_write_zeroes should be > >> padded to 512 bytes here. But when I look at the Linux sources > >> (drivers/block/virtio_blk.c), I fail to see that they are doing the > >> padding there (but maybe I'm just too blind). > >> > >> Looking at the QEMU sources, it seems like it can deal with both and > >> always sets the status right behind the last byte: > >> > >> req->in = (void *)in_iov[in_num - 1].iov_base > >> + in_iov[in_num - 1].iov_len > >> - sizeof(struct virtio_blk_inhdr); > >> > >> Anyway, I think the virtio spec should be clearer here to avoid bad > >> implementations in the future, so maybe Changpeng or Michael could > >> update the spec here a little bit? > > The data for Discard and Write Zeroes commands are struct > > virtio_blk_discard_write_zeroes > > aligned, that means you can pass 16 bytes aligned data, based on the > > segments number supported, > > this is also aligned with NVMe specification and the SCSI specification. > > Ok, thanks, so the "u8 data[][512];" is wrong in the virtio spec in this > case? See: > > https://github.com/oasis-tcs/virtio-spec/blob/master/content.tex#L3944 > > At least this should be mentioned in the description of the data field, > I think. > > Thomas
OK. Is it a multiple of 512 for all other operations?
