Re: [Qemu-devel] [PATCH 1/4] macio: switch pmac_dma_read() over to new offset/len implementation

[John Snow <jsnow@redhat.com>]

On 05/31/2015 04:05 PM, Mark Cave-Ayland wrote:
> For better handling of unaligned block device accesses.
> 
> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> ---
>  hw/ide/macio.c |  102 ++++++++++++++++++++++----------------------------------
>  1 file changed, 40 insertions(+), 62 deletions(-)
> 
> diff --git a/hw/ide/macio.c b/hw/ide/macio.c
> index 585a27b..f1ac001 100644
> --- a/hw/ide/macio.c
> +++ b/hw/ide/macio.c
> @@ -52,7 +52,7 @@ static const int debug_macio = 0;
>  #define MACIO_PAGE_SIZE 4096
>  
>  static void pmac_dma_read(BlockBackend *blk,
> -                          int64_t sector_num, int nb_sectors,
> +                          int64_t offset, unsigned int bytes,
>                            void (*cb)(void *opaque, int ret), void *opaque)
>  {
>      DBDMA_io *io = opaque;
> @@ -60,76 +60,48 @@ static void pmac_dma_read(BlockBackend *blk,
>      IDEState *s = idebus_active_if(&m->bus);
>      dma_addr_t dma_addr, dma_len;
>      void *mem;
> -    int nsector, remainder;
> +    int64_t sector_num;
> +    int nsector;
> +    uint64_t align = BDRV_SECTOR_SIZE;
> +    size_t head_bytes, tail_bytes;
>  
>      qemu_iovec_destroy(&io->iov);
>      qemu_iovec_init(&io->iov, io->len / MACIO_PAGE_SIZE + 1);
>  
> -    if (io->remainder_len > 0) {
> -        /* Return remainder of request */
> -        int transfer = MIN(io->remainder_len, io->len);
> +    sector_num = (offset >> 9);
> +    nsector = (io->len >> 9);
>  
> -        MACIO_DPRINTF("--- DMA read pop     - bounce addr: %p addr: %"
> -                      HWADDR_PRIx " remainder_len: %x\n",
> -                      &io->remainder + (0x200 - transfer), io->addr,
> -                      io->remainder_len);
> +    MACIO_DPRINTF("--- DMA read transfer (0x%" HWADDR_PRIx ",0x%x): "
> +                  "sector_num: %ld, nsector: %d\n", io->addr, io->len,
> +                  sector_num, nsector);
>  
> -        cpu_physical_memory_write(io->addr,
> -                                  &io->remainder + (0x200 - transfer),
> -                                  transfer);
> +    dma_addr = io->addr;
> +    dma_len = io->len;
> +    mem = dma_memory_map(&address_space_memory, dma_addr, &dma_len,
> +                         DMA_DIRECTION_FROM_DEVICE);
>  
> -        io->remainder_len -= transfer;
> -        io->len -= transfer;
> -        io->addr += transfer;
> +    if (offset & (align - 1)) {
> +        head_bytes = offset & (align - 1);
>  
> -        s->io_buffer_index += transfer;
> -        s->io_buffer_size -= transfer;
> +        MACIO_DPRINTF("--- DMA unaligned head: sector %ld, "
> +                      "discarding %ld bytes\n", sector_num, head_bytes);
>  
> -        if (io->remainder_len != 0) {
> -            /* Still waiting for remainder */
> -            return;
> -        }
> +        qemu_iovec_add(&io->iov, &io->remainder, head_bytes);
>  
> -        if (io->len == 0) {
> -            MACIO_DPRINTF("--- finished all read processing; go and finish\n");
> -            cb(opaque, 0);
> -            return;
> -        }
> +        bytes += offset & (align - 1);
> +        offset = offset & ~(align - 1);
>      }
>  
> -    if (s->drive_kind == IDE_CD) {
> -        sector_num = (int64_t)(s->lba << 2) + (s->io_buffer_index >> 9);
> -    } else {
> -        sector_num = ide_get_sector(s) + (s->io_buffer_index >> 9);
> -    }
> +    qemu_iovec_add(&io->iov, mem, io->len);
>  
> -    nsector = ((io->len + 0x1ff) >> 9);
> -    remainder = (nsector << 9) - io->len;
> +    if ((offset + bytes) & (align - 1)) {
> +        tail_bytes = (offset + bytes) & (align - 1);
>  
> -    MACIO_DPRINTF("--- DMA read transfer - addr: %" HWADDR_PRIx " len: %x\n",
> -                  io->addr, io->len);
> -
> -    dma_addr = io->addr;
> -    dma_len = io->len;
> -    mem = dma_memory_map(&address_space_memory, dma_addr, &dma_len,
> -                         DMA_DIRECTION_FROM_DEVICE);
> +        MACIO_DPRINTF("--- DMA unaligned tail: sector %ld, "
> +                      "discarding bytes %ld\n", sector_num, tail_bytes);
>  
> -    if (!remainder) {
> -        MACIO_DPRINTF("--- DMA read aligned - addr: %" HWADDR_PRIx
> -                      " len: %x\n", io->addr, io->len);
> -        qemu_iovec_add(&io->iov, mem, io->len);
> -    } else {
> -        MACIO_DPRINTF("--- DMA read unaligned - addr: %" HWADDR_PRIx
> -                      " len: %x\n", io->addr, io->len);
> -        qemu_iovec_add(&io->iov, mem, io->len);
> -
> -        MACIO_DPRINTF("--- DMA read push    - bounce addr: %p "
> -                      "remainder_len: %x\n",
> -                      &io->remainder + 0x200 - remainder, remainder);
> -        qemu_iovec_add(&io->iov, &io->remainder + 0x200 - remainder,
> -                       remainder);
> -
> -        io->remainder_len = remainder;
> +        qemu_iovec_add(&io->iov, &io->remainder, align - tail_bytes);
> +        bytes = ROUND_UP(bytes, align);
>      }
>  
>      s->io_buffer_size -= io->len;
> @@ -137,11 +109,11 @@ static void pmac_dma_read(BlockBackend *blk,
>  
>      io->len = 0;
>  
> -    MACIO_DPRINTF("--- Block read transfer   - sector_num: %"PRIx64"  "
> -                  "nsector: %x\n",
> -                  sector_num, nsector);
> +    MACIO_DPRINTF("--- Block read transfer - sector_num: %" PRIx64 "  "
> +                  "nsector: %x\n", (offset >> 9), (bytes >> 9));
>  
> -    m->aiocb = blk_aio_readv(blk, sector_num, &io->iov, nsector, cb, io);
> +    m->aiocb = blk_aio_readv(blk, (offset >> 9), &io->iov, (bytes >> 9),
> +                             cb, io);
>  }
>  
>  static void pmac_dma_write(BlockBackend *blk,
> @@ -246,6 +218,7 @@ static void pmac_ide_atapi_transfer_cb(void *opaque, int ret)
>      IDEState *s = idebus_active_if(&m->bus);
>      int64_t sector_num;
>      int nsector, remainder;
> +    int64_t offset;
>  
>      MACIO_DPRINTF("\ns is %p\n", s);
>      MACIO_DPRINTF("io_buffer_index: %x\n", s->io_buffer_index);
> @@ -294,10 +267,13 @@ static void pmac_ide_atapi_transfer_cb(void *opaque, int ret)
>      nsector = (io->len + 0x1ff) >> 9;
>      remainder = io->len & 0x1ff;
>  
> +    /* Calculate current offset */
> +    offset = (int64_t)(s->lba << 11) + s->io_buffer_index;
> +

Bike shedding: Worth an ATAPI_BLOCK_SIZE_BITS define or similar? I guess
we don't really currently try to avoid magic constants for 512, 2048,
etc etc anywhere else, so ... nevermind. Just a project for a different
day. Forget I said anything.

>      MACIO_DPRINTF("nsector: %d   remainder: %x\n", nsector, remainder);
>      MACIO_DPRINTF("sector: %"PRIx64"   %zx\n", sector_num, io->iov.size / 512);
>  
> -    pmac_dma_read(s->blk, sector_num, nsector, pmac_ide_atapi_transfer_cb, io);
> +    pmac_dma_read(s->blk, offset, io->len, pmac_ide_atapi_transfer_cb, io);
>      return;
>  
>  done:
> @@ -315,6 +291,7 @@ static void pmac_ide_transfer_cb(void *opaque, int ret)
>      IDEState *s = idebus_active_if(&m->bus);
>      int64_t sector_num;
>      int nsector, remainder;
> +    int64_t offset;
>  
>      MACIO_DPRINTF("pmac_ide_transfer_cb\n");
>  
> @@ -349,6 +326,7 @@ static void pmac_ide_transfer_cb(void *opaque, int ret)
>  
>      /* Calculate number of sectors */
>      sector_num = ide_get_sector(s) + (s->io_buffer_index >> 9);
> +    offset = (ide_get_sector(s) << 9) + s->io_buffer_index;
>      nsector = (io->len + 0x1ff) >> 9;
>      remainder = io->len & 0x1ff;
>  
> @@ -359,7 +337,7 @@ static void pmac_ide_transfer_cb(void *opaque, int ret)
>  
>      switch (s->dma_cmd) {
>      case IDE_DMA_READ:
> -        pmac_dma_read(s->blk, sector_num, nsector, pmac_ide_transfer_cb, io);
> +        pmac_dma_read(s->blk, offset, io->len, pmac_ide_transfer_cb, io);
>          break;
>      case IDE_DMA_WRITE:
>          pmac_dma_write(s->blk, sector_num, nsector, pmac_ide_transfer_cb, io);
>