Commit bef0fd59 authored by Stefan Hajnoczi's avatar Stefan Hajnoczi Committed by Kevin Wolf
Browse files

ide: convert ide_sector_read() to asynchronous I/O 



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: default avatarStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: default avatarZhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Tested-by: default avatarRichard Davies <richard@arachsys.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 592fa070

hw/ide/core.c

+55 −21
Original line number Diff line number Diff line
@@ -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 {

        return;

    }



    s->status |= BUSY_STAT;



    if (n > s->req_nb_sectors) {

        n = s->req_nb_sectors;

    }



#if defined(DEBUG_IDE)

        printf("read sector=%" PRId64 "\n", sector_num);

    printf("sector=%" PRId64 "\n", sector_num);

#endif

        if (n > s->req_nb_sectors)

            n = s->req_nb_sectors;



    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);

        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;

    }

    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

hw/ide/internal.h

+3 −0
Original line number Diff line number Diff line
@@ -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;