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ide: convert ide_sector_read() to asynchronous I/O

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The IDE PIO interface currently uses bdrv_read() to perform reads
synchronously.  Synchronous I/O in the vcpu thread is bad because it
prevents the guest from executing code - it makes the guest
unresponsive.

This patch converts IDE PIO to use bdrv_aio_readv().  We simply need to
use the BUSY_STAT status so the guest knows to wait while we are busy.

The only external user of ide_sector_read() is restart behavior on I/O
errors and it is not affected by this change.  We still need to restart
I/O in the same way.

Migration is also unaffected if I understand the code correctly.  We
continue to use the same transfer function and the BUSY_STAT status
should never be migrated since we flush I/O before migrating device
state.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Tested-by: Richard Davies <richard@arachsys.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2012-03-29 10:31:30 +01:00 committed by Kevin Wolf
parent 592fa07043
commit bef0fd5958
2 changed files with 61 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

82
hw/ide/core.c
View File

@ -471,40 +471,68 @@ static void ide_rw_error(IDEState *s) {
ide_set_irq(s->bus);
}
static void ide_sector_read_cb(void *opaque, int ret)
{
IDEState *s = opaque;
int n;
s->pio_aiocb = NULL;
s->status &= ~BUSY_STAT;
bdrv_acct_done(s->bs, &s->acct);
if (ret != 0) {
if (ide_handle_rw_error(s, -ret, BM_STATUS_PIO_RETRY |
BM_STATUS_RETRY_READ)) {
return;
}
}
n = s->nsector;
if (n > s->req_nb_sectors) {
n = s->req_nb_sectors;
}
/* Allow the guest to read the io_buffer */
ide_transfer_start(s, s->io_buffer, n * BDRV_SECTOR_SIZE, ide_sector_read);
ide_set_irq(s->bus);
ide_set_sector(s, ide_get_sector(s) + n);
s->nsector -= n;
}
void ide_sector_read(IDEState *s)
{
int64_t sector_num;
int ret, n;
int n;
s->status = READY_STAT | SEEK_STAT;
s->error = 0; /* not needed by IDE spec, but needed by Windows */
sector_num = ide_get_sector(s);
n = s->nsector;
if (n == 0) {
/* no more sector to read from disk */
ide_transfer_stop(s);
} else {
#if defined(DEBUG_IDE)
printf("read sector=%" PRId64 "\n", sector_num);
#endif
if (n > s->req_nb_sectors)
n = s->req_nb_sectors;
bdrv_acct_start(s->bs, &s->acct, n * BDRV_SECTOR_SIZE, BDRV_ACCT_READ);
ret = bdrv_read(s->bs, sector_num, s->io_buffer, n);
bdrv_acct_done(s->bs, &s->acct);
if (ret != 0) {
if (ide_handle_rw_error(s, -ret,
BM_STATUS_PIO_RETRY | BM_STATUS_RETRY_READ))
{
return;
}
}
ide_transfer_start(s, s->io_buffer, 512 * n, ide_sector_read);
ide_set_irq(s->bus);
ide_set_sector(s, sector_num + n);
s->nsector -= n;
if (n == 0) {
ide_transfer_stop(s);
return;
}
s->status |= BUSY_STAT;
if (n > s->req_nb_sectors) {
n = s->req_nb_sectors;
}
#if defined(DEBUG_IDE)
printf("sector=%" PRId64 "\n", sector_num);
#endif
s->iov.iov_base = s->io_buffer;
s->iov.iov_len = n * BDRV_SECTOR_SIZE;
qemu_iovec_init_external(&s->qiov, &s->iov, 1);
bdrv_acct_start(s->bs, &s->acct, n * BDRV_SECTOR_SIZE, BDRV_ACCT_READ);
s->pio_aiocb = bdrv_aio_readv(s->bs, sector_num, &s->qiov, n,
ide_sector_read_cb, s);
}
static void dma_buf_commit(IDEState *s)
@ -1765,6 +1793,12 @@ static void ide_reset(IDEState *s)
#ifdef DEBUG_IDE
printf("ide: reset\n");
#endif
if (s->pio_aiocb) {
bdrv_aio_cancel(s->pio_aiocb);
s->pio_aiocb = NULL;
}
if (s->drive_kind == IDE_CFATA)
s->mult_sectors = 0;
else

3
hw/ide/internal.h
View File

@ -385,6 +385,9 @@ struct IDEState {
int cd_sector_size;
int atapi_dma; /* true if dma is requested for the packet cmd */
BlockAcctCookie acct;
BlockDriverAIOCB *pio_aiocb;
struct iovec iov;
QEMUIOVector qiov;
/* ATA DMA state */
int io_buffer_size;
QEMUSGList sg;