On 05/23/2016 06:54 AM, Paolo Bonzini wrote:
> Using pread/pwrite or io_submit has the advantage of eliminating the
> bounce buffer, but drops the SCSI status. This keeps the guest from
> seeing unit attention codes, as well as statuses such as RESERVATION
> CONFLICT. Because we know scsi-block operates on an SBC device we can
> still use the DMA helpers with SG_IO; just remember to patch the CDBs
> if the transfer is split into multiple segments.
>
> This means that scsi-block will always use the thread-pool unfortunately,
> instead of respecting aio=native.
>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> hw/scsi/scsi-disk.c | 214
> +++++++++++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 196 insertions(+), 18 deletions(-)
>
> diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
> index f823781..c0eefc0 100644
> --- a/hw/scsi/scsi-disk.c
> +++ b/hw/scsi/scsi-disk.c
> @@ -83,6 +83,7 @@ typedef struct SCSIDiskReq {
> struct iovec iov;
> QEMUIOVector qiov;
> BlockAcctCookie acct;
> + unsigned char *status;
> } SCSIDiskReq;
>
> #define SCSI_DISK_F_REMOVABLE 0
> @@ -190,6 +191,15 @@ static bool scsi_disk_req_check_error(SCSIDiskReq *r,
> int ret, bool acct_failed)
> return scsi_handle_rw_error(r, -ret, acct_failed);
> }
>
> + if (r->status && *r->status) {
> + if (acct_failed) {
> + SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
Another use of DO_UPCAST(); would container_of() be better?
> +
> +static BlockAIOCB *scsi_block_do_sgio(SCSIBlockReq *req,
> + int64_t offset, QEMUIOVector *iov,
> + int direction,
> + BlockCompletionFunc *cb, void *opaque)
> +{
> + sg_io_hdr_t *io_header = &req->io_header;
> + SCSIDiskReq *r = &req->req;
> + SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
> + int nb_logical_blocks;
> + uint64_t lba;
> + BlockAIOCB *aiocb;
> +
> + /* This is not supported yet. It can only happen if the guest does
> + * reads and writes that are not aligned to one logical sectors
s/one // ?
> + * _and_ cover multiple MemoryRegions.
> + */
> + assert(offset % s->qdev.blocksize == 0);
> + assert(iov->size % s->qdev.blocksize == 0);
Is asserting for something an ill-behaved guest can do the right behavior?
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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