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scsi-disk: lazily allocate bounce buffer 

It will not be needed for reads and writes if the HBA provides a sglist.
In addition, this lets scsi-disk refuse commands with an excessive
allocation length, as well as limit memory on usual well-behaved guests.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Paolo Bonzini 2011-09-16 16:40:04 +02:00 committed by Kevin Wolf
parent 103b40f51e
commit 7285477ab1
1 changed files with 33 additions and 11 deletions
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44
hw/scsi-disk.c
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@ -55,6 +55,7 @@ typedef struct SCSIDiskReq {
/* Both sector and sector_count are in terms of qemu 512 byte blocks. */
uint64_t sector;
uint32_t sector_count;
uint32_t buflen;
struct iovec iov;
QEMUIOVector qiov;
uint32_t status;
@ -78,13 +79,15 @@ struct SCSIDiskState
};
static int scsi_handle_rw_error(SCSIDiskReq *r, int error, int type);
static int scsi_disk_emulate_command(SCSIDiskReq *r, uint8_t *outbuf);
static int scsi_disk_emulate_command(SCSIDiskReq *r);
static void scsi_free_request(SCSIRequest *req)
{
SCSIDiskReq *r = DO_UPCAST(SCSIDiskReq, req, req);
qemu_vfree(r->iov.iov_base);
if (r->iov.iov_base) {
qemu_vfree(r->iov.iov_base);
}
}
/* Helper function for command completion with sense. */
@ -110,7 +113,13 @@ static void scsi_cancel_io(SCSIRequest *req)
static uint32_t scsi_init_iovec(SCSIDiskReq *r)
{
r->iov.iov_len = MIN(r->sector_count * 512, SCSI_DMA_BUF_SIZE);
SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
if (!r->iov.iov_base) {
r->buflen = SCSI_DMA_BUF_SIZE;
r->iov.iov_base = qemu_blockalign(s->bs, r->buflen);
}
r->iov.iov_len = MIN(r->sector_count * 512, r->buflen);
qemu_iovec_init_external(&r->qiov, &r->iov, 1);
return r->qiov.size / 512;
}
@ -323,7 +332,7 @@ static void scsi_dma_restart_bh(void *opaque)
scsi_write_data(&r->req);
break;
case SCSI_REQ_STATUS_RETRY_FLUSH:
ret = scsi_disk_emulate_command(r, r->iov.iov_base);
ret = scsi_disk_emulate_command(r);
if (ret == 0) {
scsi_req_complete(&r->req, GOOD);
}
@ -838,13 +847,31 @@ static int scsi_disk_emulate_start_stop(SCSIDiskReq *r)
return 0;
}
static int scsi_disk_emulate_command(SCSIDiskReq *r, uint8_t *outbuf)
static int scsi_disk_emulate_command(SCSIDiskReq *r)
{
SCSIRequest *req = &r->req;
SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, req->dev);
uint64_t nb_sectors;
uint8_t *outbuf;
int buflen = 0;
if (!r->iov.iov_base) {
/*
* FIXME: we shouldn't return anything bigger than 4k, but the code
* requires the buffer to be as big as req->cmd.xfer in several
* places. So, do not allow CDBs with a very large ALLOCATION
* LENGTH. The real fix would be to modify scsi_read_data and
* dma_buf_read, so that they return data beyond the buflen
* as all zeros.
*/
if (req->cmd.xfer > 65536) {
goto illegal_request;
}
r->buflen = MAX(4096, req->cmd.xfer);
r->iov.iov_base = qemu_blockalign(s->bs, r->buflen);
}
outbuf = r->iov.iov_base;
switch (req->cmd.buf[0]) {
case TEST_UNIT_READY:
if (s->tray_open || !bdrv_is_inserted(s->bs))
@ -995,11 +1022,9 @@ static int32_t scsi_send_command(SCSIRequest *req, uint8_t *buf)
SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, req->dev);
int32_t len;
uint8_t command;
uint8_t *outbuf;
int rc;
command = buf[0];
outbuf = (uint8_t *)r->iov.iov_base;
DPRINTF("Command: lun=%d tag=0x%x data=0x%02x", req->lun, req->tag, buf[0]);
#ifdef DEBUG_SCSI
@ -1028,7 +1053,7 @@ static int32_t scsi_send_command(SCSIRequest *req, uint8_t *buf)
case GET_CONFIGURATION:
case SERVICE_ACTION_IN_16:
case VERIFY_10:
rc = scsi_disk_emulate_command(r, outbuf);
rc = scsi_disk_emulate_command(r);
if (rc < 0) {
return 0;
}
@ -1279,11 +1304,8 @@ static SCSIRequest *scsi_new_request(SCSIDevice *d, uint32_t tag,
{
SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, d);
SCSIRequest *req;
SCSIDiskReq *r;
req = scsi_req_alloc(&scsi_disk_reqops, &s->qdev, tag, lun, hba_private);
r = DO_UPCAST(SCSIDiskReq, req, req);
r->iov.iov_base = qemu_blockalign(s->bs, SCSI_DMA_BUF_SIZE);
return req;
}