Message ID | 1332486440-12512-1-git-send-email-zhihuili@linux.vnet.ibm.com |
---|---|
State | New |
Headers | show |
On Fri, Mar 23, 2012 at 03:07:20PM +0800, Li Zhi Hui wrote: > Replace bdrv_* to bdrv_aio_* functions in pio mode in fdc.c. > > Signed-off-by: Li Zhi Hui <zhihuili@linux.vnet.ibm.com> > --- > hw/fdc.c | 117 +++++++++++++++++++++++++++++++++++++++++++++++-------------- > 1 files changed, 90 insertions(+), 27 deletions(-) I have posted detailed comments below. The high-level point is to look back at the datasheet because the information needed to implement asynchronous I/O is only available there. Since hw/fdc.c is synchronous today it omits steps in the request lifecycle that are necessary for asynchronous I/O. It is impossible to do asynchronous I/O by refactoring hw/fdc.c, it won't produce the semantics from the datasheet. You need to study the request lifecycle in the datasheet and use that information to implement asynchronous I/O in hw/fdc.c. > diff --git a/hw/fdc.c b/hw/fdc.c > index a0236b7..5e855fd 100644 > --- a/hw/fdc.c > +++ b/hw/fdc.c > @@ -1301,12 +1301,42 @@ static int fdctrl_transfer_handler (void *opaque, int nchan, > return len; > } > > +enum { > + FD_DATA_IDLE, > + FD_DATA_WORKING, > + FD_DATA_FIN, > +}; > + > +int data_status[MAX_FD]; This would need to be a FDCtrl field so that each FDrive on each fdc instance has it's own data_status. If you leave it global then it's not possible to use multiple fdc devices at the same time. > + > +static void fdctrl_read_pio_cb(void *opaque, int ret) > +{ > + FDCtrl *fdctrl = opaque; > + FDrive *cur_drv; > + > + if (ret < 0) { > + cur_drv = get_cur_drv(fdctrl); > + FLOPPY_DPRINTF("error getting sector %d\n", > + fd_sector(cur_drv)); > + /* Sure, image size is too small... */ > + memset(fdctrl->fifo, 0, FD_SECTOR_LEN); > + data_status[fdctrl->cur_drv] = FD_DATA_IDLE; > + goto end; > + } > + data_status[fdctrl->cur_drv] = FD_DATA_FIN; > + > +end: > + return; > +} > + > /* Data register : 0x05 */ > static uint32_t fdctrl_read_data(FDCtrl *fdctrl) > { > FDrive *cur_drv; > uint32_t retval = 0; > int pos; > + QEMUIOVector qiov; > + struct iovec iov; > > cur_drv = get_cur_drv(fdctrl); > fdctrl->dsr &= ~FD_DSR_PWRDOWN; > @@ -1318,17 +1348,30 @@ static uint32_t fdctrl_read_data(FDCtrl *fdctrl) > if (fdctrl->msr & FD_MSR_NONDMA) { > pos %= FD_SECTOR_LEN; > if (pos == 0) { > - if (fdctrl->data_pos != 0) > - if (!fdctrl_seek_to_next_sect(fdctrl, cur_drv)) { > - FLOPPY_DPRINTF("error seeking to next sector %d\n", > - fd_sector(cur_drv)); > - return 0; > + switch (data_status[fdctrl->cur_drv]) { > + case FD_DATA_IDLE: > + if (fdctrl->data_pos != 0) { > + if (!fdctrl_seek_to_next_sect(fdctrl, cur_drv)) { > + FLOPPY_DPRINTF("error seeking to next sector %d\n", > + fd_sector(cur_drv)); > + goto end; > + } > } > - if (bdrv_read(cur_drv->bs, fd_sector(cur_drv), fdctrl->fifo, 1) < 0) { > - FLOPPY_DPRINTF("error getting sector %d\n", > - fd_sector(cur_drv)); > - /* Sure, image size is too small... */ > - memset(fdctrl->fifo, 0, FD_SECTOR_LEN); > + iov.iov_base = fdctrl->fifo; > + iov.iov_len = FD_SECTOR_LEN; > + qemu_iovec_init_external(&qiov, &iov, 1); > + bdrv_aio_readv(cur_drv->bs, fd_sector(cur_drv), > + &qiov, 1, fdctrl_read_pio_cb, fdctrl); > + data_status[fdctrl->cur_drv] = FD_DATA_WORKING; > + goto end; > + case FD_DATA_WORKING: > + goto end; > + case FD_DATA_FIN: > + data_status[fdctrl->cur_drv] = FD_DATA_IDLE; > + break; > + default: > + data_status[fdctrl->cur_drv] = FD_DATA_IDLE; > + goto end; > } Does this approach follow the datasheet? You are returning 0 on each "goto end" so the guest will think it is reading zeroes from the floppy. When fdctrl_read_data() gets called we *must* have valid data in the fifo - or be able to tell the guest to wait using status register bits. > } > } > @@ -1347,6 +1390,7 @@ static uint32_t fdctrl_read_data(FDCtrl *fdctrl) > } > FLOPPY_DPRINTF("data register: 0x%02x\n", retval); > > +end: > return retval; > } > > @@ -1759,10 +1803,38 @@ static const struct { > /* Associate command to an index in the 'handlers' array */ > static uint8_t command_to_handler[256]; > > +static void fdctrl_write_pio_cb(void *opaque, int ret) > +{ > + FDCtrl *fdctrl = opaque; > + FDrive *cur_drv; > + > + cur_drv = get_cur_drv(fdctrl); > + if (ret < 0) { > + FLOPPY_ERROR("writing sector %d\n", fd_sector(cur_drv)); > + goto end; > + } > + if (!fdctrl_seek_to_next_sect(fdctrl, cur_drv)) { > + FLOPPY_DPRINTF("error seeking to next sector %d\n", > + fd_sector(cur_drv)); > + goto end; > + } > + /* Switch from transfer mode to status mode > + * then from status mode to command mode > + */ > + if (fdctrl->data_pos == fdctrl->data_len) { > + fdctrl_stop_transfer(fdctrl, FD_SR0_SEEK, 0x00, 0x00); > + } > + > +end: > + return; > +} > + > static void fdctrl_write_data(FDCtrl *fdctrl, uint32_t value) > { > FDrive *cur_drv; > int pos; > + QEMUIOVector qiov; > + struct iovec iov; bdrv_aio_*() does not copy qiov, it just takes a reference. This means qiov/iov's lifetime must extend beyond bdrv_aio_*() completion. It's not safe to allocate these variables on the stack since fdctrl_write_data() will return. I suggest making qiov/iov FDCtrl fields because I think a floppy controller can only perform one request at a time. > > /* Reset mode */ > if (!(fdctrl->dor & FD_DOR_nRESET)) { > @@ -1780,25 +1852,16 @@ static void fdctrl_write_data(FDCtrl *fdctrl, uint32_t value) > pos = fdctrl->data_pos++; > pos %= FD_SECTOR_LEN; > fdctrl->fifo[pos] = value; > - if (pos == FD_SECTOR_LEN - 1 || > - fdctrl->data_pos == fdctrl->data_len) { > + if ((pos == FD_SECTOR_LEN - 1) || > + (fdctrl->data_pos == fdctrl->data_len)) { > cur_drv = get_cur_drv(fdctrl); > - if (bdrv_write(cur_drv->bs, fd_sector(cur_drv), fdctrl->fifo, 1) < 0) { > - FLOPPY_ERROR("writing sector %d\n", fd_sector(cur_drv)); > - return; > - } > - if (!fdctrl_seek_to_next_sect(fdctrl, cur_drv)) { > - FLOPPY_DPRINTF("error seeking to next sector %d\n", > - fd_sector(cur_drv)); > - return; > - } > + iov.iov_base = fdctrl->fifo; > + iov.iov_len = FD_SECTOR_LEN; > + qemu_iovec_init_external(&qiov, &iov, 1); > + bdrv_aio_writev(cur_drv->bs, fd_sector(cur_drv), > + &qiov, 1, fdctrl_write_pio_cb, fdctrl); > + return; > } > - /* Switch from transfer mode to status mode > - * then from status mode to command mode > - */ > - if (fdctrl->data_pos == fdctrl->data_len) > - fdctrl_stop_transfer(fdctrl, FD_SR0_SEEK, 0x00, 0x00); > - return; > } > if (fdctrl->data_pos == 0) { > /* Command */ fdctrl_write_data() fills the fifo and submits bdrv_aio_write() requests but doesn't tell the guest to stop writing more data to the fifo. The guest may continue to call fdctrl_write_data() before we've completed the last sector write. So the guest can overwrite the fifo and the write will be corrupted. Does the floppy controller datasheet describe a status bit which is used to indicate that the fifo is busy? Previously we didn't need to use it because bdrv_write() was "atomic", but now we need to tell the guest to wait while we write the sector. Stefan
diff --git a/hw/fdc.c b/hw/fdc.c index a0236b7..5e855fd 100644 --- a/hw/fdc.c +++ b/hw/fdc.c @@ -1301,12 +1301,42 @@ static int fdctrl_transfer_handler (void *opaque, int nchan, return len; } +enum { + FD_DATA_IDLE, + FD_DATA_WORKING, + FD_DATA_FIN, +}; + +int data_status[MAX_FD]; + +static void fdctrl_read_pio_cb(void *opaque, int ret) +{ + FDCtrl *fdctrl = opaque; + FDrive *cur_drv; + + if (ret < 0) { + cur_drv = get_cur_drv(fdctrl); + FLOPPY_DPRINTF("error getting sector %d\n", + fd_sector(cur_drv)); + /* Sure, image size is too small... */ + memset(fdctrl->fifo, 0, FD_SECTOR_LEN); + data_status[fdctrl->cur_drv] = FD_DATA_IDLE; + goto end; + } + data_status[fdctrl->cur_drv] = FD_DATA_FIN; + +end: + return; +} + /* Data register : 0x05 */ static uint32_t fdctrl_read_data(FDCtrl *fdctrl) { FDrive *cur_drv; uint32_t retval = 0; int pos; + QEMUIOVector qiov; + struct iovec iov; cur_drv = get_cur_drv(fdctrl); fdctrl->dsr &= ~FD_DSR_PWRDOWN; @@ -1318,17 +1348,30 @@ static uint32_t fdctrl_read_data(FDCtrl *fdctrl) if (fdctrl->msr & FD_MSR_NONDMA) { pos %= FD_SECTOR_LEN; if (pos == 0) { - if (fdctrl->data_pos != 0) - if (!fdctrl_seek_to_next_sect(fdctrl, cur_drv)) { - FLOPPY_DPRINTF("error seeking to next sector %d\n", - fd_sector(cur_drv)); - return 0; + switch (data_status[fdctrl->cur_drv]) { + case FD_DATA_IDLE: + if (fdctrl->data_pos != 0) { + if (!fdctrl_seek_to_next_sect(fdctrl, cur_drv)) { + FLOPPY_DPRINTF("error seeking to next sector %d\n", + fd_sector(cur_drv)); + goto end; + } } - if (bdrv_read(cur_drv->bs, fd_sector(cur_drv), fdctrl->fifo, 1) < 0) { - FLOPPY_DPRINTF("error getting sector %d\n", - fd_sector(cur_drv)); - /* Sure, image size is too small... */ - memset(fdctrl->fifo, 0, FD_SECTOR_LEN); + iov.iov_base = fdctrl->fifo; + iov.iov_len = FD_SECTOR_LEN; + qemu_iovec_init_external(&qiov, &iov, 1); + bdrv_aio_readv(cur_drv->bs, fd_sector(cur_drv), + &qiov, 1, fdctrl_read_pio_cb, fdctrl); + data_status[fdctrl->cur_drv] = FD_DATA_WORKING; + goto end; + case FD_DATA_WORKING: + goto end; + case FD_DATA_FIN: + data_status[fdctrl->cur_drv] = FD_DATA_IDLE; + break; + default: + data_status[fdctrl->cur_drv] = FD_DATA_IDLE; + goto end; } } } @@ -1347,6 +1390,7 @@ static uint32_t fdctrl_read_data(FDCtrl *fdctrl) } FLOPPY_DPRINTF("data register: 0x%02x\n", retval); +end: return retval; } @@ -1759,10 +1803,38 @@ static const struct { /* Associate command to an index in the 'handlers' array */ static uint8_t command_to_handler[256]; +static void fdctrl_write_pio_cb(void *opaque, int ret) +{ + FDCtrl *fdctrl = opaque; + FDrive *cur_drv; + + cur_drv = get_cur_drv(fdctrl); + if (ret < 0) { + FLOPPY_ERROR("writing sector %d\n", fd_sector(cur_drv)); + goto end; + } + if (!fdctrl_seek_to_next_sect(fdctrl, cur_drv)) { + FLOPPY_DPRINTF("error seeking to next sector %d\n", + fd_sector(cur_drv)); + goto end; + } + /* Switch from transfer mode to status mode + * then from status mode to command mode + */ + if (fdctrl->data_pos == fdctrl->data_len) { + fdctrl_stop_transfer(fdctrl, FD_SR0_SEEK, 0x00, 0x00); + } + +end: + return; +} + static void fdctrl_write_data(FDCtrl *fdctrl, uint32_t value) { FDrive *cur_drv; int pos; + QEMUIOVector qiov; + struct iovec iov; /* Reset mode */ if (!(fdctrl->dor & FD_DOR_nRESET)) { @@ -1780,25 +1852,16 @@ static void fdctrl_write_data(FDCtrl *fdctrl, uint32_t value) pos = fdctrl->data_pos++; pos %= FD_SECTOR_LEN; fdctrl->fifo[pos] = value; - if (pos == FD_SECTOR_LEN - 1 || - fdctrl->data_pos == fdctrl->data_len) { + if ((pos == FD_SECTOR_LEN - 1) || + (fdctrl->data_pos == fdctrl->data_len)) { cur_drv = get_cur_drv(fdctrl); - if (bdrv_write(cur_drv->bs, fd_sector(cur_drv), fdctrl->fifo, 1) < 0) { - FLOPPY_ERROR("writing sector %d\n", fd_sector(cur_drv)); - return; - } - if (!fdctrl_seek_to_next_sect(fdctrl, cur_drv)) { - FLOPPY_DPRINTF("error seeking to next sector %d\n", - fd_sector(cur_drv)); - return; - } + iov.iov_base = fdctrl->fifo; + iov.iov_len = FD_SECTOR_LEN; + qemu_iovec_init_external(&qiov, &iov, 1); + bdrv_aio_writev(cur_drv->bs, fd_sector(cur_drv), + &qiov, 1, fdctrl_write_pio_cb, fdctrl); + return; } - /* Switch from transfer mode to status mode - * then from status mode to command mode - */ - if (fdctrl->data_pos == fdctrl->data_len) - fdctrl_stop_transfer(fdctrl, FD_SR0_SEEK, 0x00, 0x00); - return; } if (fdctrl->data_pos == 0) { /* Command */
Replace bdrv_* to bdrv_aio_* functions in pio mode in fdc.c. Signed-off-by: Li Zhi Hui <zhihuili@linux.vnet.ibm.com> --- hw/fdc.c | 117 +++++++++++++++++++++++++++++++++++++++++++++++-------------- 1 files changed, 90 insertions(+), 27 deletions(-)