[Qemu-devel] [PATCH 2/4] macio: switch pmac_dma_write() over to new offset/len implementation

[Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>]

In particular, this fixes a bug whereby chains of overlapping head/tail chains
would incorrectly write over each other's remainder cache. This is the access
pattern used by OS X/Darwin and fixes an issue with a corrupt Darwin
installation in my local tests.

While we are here, rename the DBDMA_io struct property remainder to
head_remainder for clarification.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
---
 hw/ide/macio.c             |  116 ++++++++++++++++++++------------------------
 include/hw/ppc/mac_dbdma.h |    3 +-
 2 files changed, 55 insertions(+), 64 deletions(-)

diff --git a/hw/ide/macio.c b/hw/ide/macio.c
index f1ac001..92f35e2 100644
--- a/hw/ide/macio.c
+++ b/hw/ide/macio.c
@@ -86,7 +86,7 @@ static void pmac_dma_read(BlockBackend *blk,
         MACIO_DPRINTF("--- DMA unaligned head: sector %ld, "
                       "discarding %ld bytes\n", sector_num, head_bytes);
 
-        qemu_iovec_add(&io->iov, &io->remainder, head_bytes);
+        qemu_iovec_add(&io->iov, &io->head_remainder, head_bytes);
 
         bytes += offset & (align - 1);
         offset = offset & ~(align - 1);
@@ -100,7 +100,7 @@ static void pmac_dma_read(BlockBackend *blk,
         MACIO_DPRINTF("--- DMA unaligned tail: sector %ld, "
                       "discarding bytes %ld\n", sector_num, tail_bytes);
 
-        qemu_iovec_add(&io->iov, &io->remainder, align - tail_bytes);
+        qemu_iovec_add(&io->iov, &io->tail_remainder, align - tail_bytes);
         bytes = ROUND_UP(bytes, align);
     }
 
@@ -117,7 +117,7 @@ static void pmac_dma_read(BlockBackend *blk,
 }
 
 static void pmac_dma_write(BlockBackend *blk,
-                         int64_t sector_num, int nb_sectors,
+                         int64_t offset, int bytes,
                          void (*cb)(void *opaque, int ret), void *opaque)
 {
     DBDMA_io *io = opaque;
@@ -125,90 +125,80 @@ static void pmac_dma_write(BlockBackend *blk,
     IDEState *s = idebus_active_if(&m->bus);
     dma_addr_t dma_addr, dma_len;
     void *mem;
-    int nsector, remainder;
-    int extra = 0;
+    int64_t sector_num;
+    int nsector;
+    uint64_t align = BDRV_SECTOR_SIZE;
+    size_t head_bytes, tail_bytes;
+    bool unaligned_head = false, unaligned_tail = false;
 
     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("--- processing write remainder %x\n", transfer);
-        cpu_physical_memory_read(io->addr,
-                                 &io->remainder + (0x200 - transfer),
-                                 transfer);
+    MACIO_DPRINTF("--- DMA write transfer (0x%" HWADDR_PRIx ",0x%x): "
+                  "sector_num: %ld, nsector: %d\n", io->addr, io->len,
+                  sector_num, nsector);
 
-        io->remainder_len -= transfer;
-        io->len -= transfer;
-        io->addr += transfer;
+    dma_addr = io->addr;
+    dma_len = io->len;
+    mem = dma_memory_map(&address_space_memory, dma_addr, &dma_len,
+                         DMA_DIRECTION_TO_DEVICE);
 
-        s->io_buffer_index += transfer;
-        s->io_buffer_size -= transfer;
+    if (offset & (align - 1)) {
+        head_bytes = offset & (align - 1);
+        sector_num = ((offset & ~(align - 1)) >> 9);
 
-        if (io->remainder_len != 0) {
-            /* Still waiting for remainder */
-            return;
-        }
+        MACIO_DPRINTF("--- DMA unaligned head: pre-reading head sector %ld\n",
+                      sector_num);
 
-        MACIO_DPRINTF("--> prepending bounce buffer with size 0x200\n");
+        blk_pread(s->blk, (sector_num << 9), &io->head_remainder, align);
 
-        /* Sector transfer complete - prepend to request */
-        qemu_iovec_add(&io->iov, &io->remainder, 0x200);
-        extra = 1;
-    }
+        qemu_iovec_add(&io->iov, &io->head_remainder, head_bytes);
+        qemu_iovec_add(&io->iov, mem, io->len);
 
-    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);
+        bytes += offset & (align - 1);
+        offset = offset & ~(align - 1);
+
+        unaligned_head = true;
     }
 
-    nsector = (io->len >> 9);
-    remainder = io->len - (nsector << 9);
+    if ((offset + bytes) & (align - 1)) {
+        tail_bytes = (offset + bytes) & (align - 1);
+        sector_num = (((offset + bytes) & ~(align - 1)) >> 9);
 
-    MACIO_DPRINTF("--- DMA write transfer - addr: %" HWADDR_PRIx " len: %x\n",
-                  io->addr, io->len);
-    MACIO_DPRINTF("xxx remainder: %x\n", remainder);
-    MACIO_DPRINTF("xxx sector_num: %"PRIx64"   nsector: %x\n",
-                  sector_num, nsector);
+        MACIO_DPRINTF("--- DMA unaligned tail: pre-reading tail sector %ld\n",
+                      sector_num);
 
-    dma_addr = io->addr;
-    dma_len = io->len;
-    mem = dma_memory_map(&address_space_memory, dma_addr, &dma_len,
-                         DMA_DIRECTION_TO_DEVICE);
+        blk_pread(s->blk, (sector_num << 9), &io->tail_remainder, align);
 
-    if (!remainder) {
-        MACIO_DPRINTF("--- DMA write aligned - addr: %" HWADDR_PRIx
-                      " len: %x\n", io->addr, io->len);
-        qemu_iovec_add(&io->iov, mem, io->len);
-    } else {
-        /* Write up to last complete sector */
-        MACIO_DPRINTF("--- DMA write unaligned - addr: %" HWADDR_PRIx
-                      " len: %x\n", io->addr, (nsector << 9));
-        qemu_iovec_add(&io->iov, mem, (nsector << 9));
+        if (!unaligned_head) {
+            qemu_iovec_add(&io->iov, mem, io->len);
+        }
 
-        MACIO_DPRINTF("--- DMA write read    - bounce addr: %p "
-                      "remainder_len: %x\n", &io->remainder, remainder);
-        cpu_physical_memory_read(io->addr + (nsector << 9), &io->remainder,
-                                 remainder);
+        qemu_iovec_add(&io->iov, &io->tail_remainder + tail_bytes,
+                       align - tail_bytes);
+
+        bytes = ROUND_UP(bytes, align);
 
-        io->remainder_len = 0x200 - remainder;
+        unaligned_tail = true;
+    }
 
-        MACIO_DPRINTF("xxx remainder_len: %x\n", io->remainder_len);
+    if (!unaligned_head && !unaligned_tail) {
+        qemu_iovec_add(&io->iov, mem, io->len);
     }
 
-    s->io_buffer_size -= ((nsector + extra) << 9);
-    s->io_buffer_index += ((nsector + extra) << 9);
+    s->io_buffer_size -= io->len;
+    s->io_buffer_index += io->len;
 
     io->len = 0;
 
-    MACIO_DPRINTF("--- Block write transfer   - sector_num: %"PRIx64"  "
-                  "nsector: %x\n", sector_num, nsector + extra);
+    MACIO_DPRINTF("--- Block write transfer - sector_num: %" PRIx64 "  "
+                  "nsector: %x\n", (offset >> 9), (bytes >> 9));
 
-    m->aiocb = blk_aio_writev(blk, sector_num, &io->iov, nsector + extra, cb,
-                              io);
+    m->aiocb = blk_aio_writev(blk, (offset >> 9), &io->iov, (bytes >> 9),
+                              cb, io);
 }
 
 static void pmac_ide_atapi_transfer_cb(void *opaque, int ret)
@@ -340,7 +330,7 @@ static void pmac_ide_transfer_cb(void *opaque, int ret)
         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);
+        pmac_dma_write(s->blk, offset, io->len, pmac_ide_transfer_cb, io);
         break;
     case IDE_DMA_TRIM:
         MACIO_DPRINTF("TRIM command issued!");
diff --git a/include/hw/ppc/mac_dbdma.h b/include/hw/ppc/mac_dbdma.h
index c580327..7f247fa 100644
--- a/include/hw/ppc/mac_dbdma.h
+++ b/include/hw/ppc/mac_dbdma.h
@@ -40,7 +40,8 @@ struct DBDMA_io {
     /* DMA is in progress, don't start another one */
     bool processing;
     /* unaligned last sector of a request */
-    uint8_t remainder[0x200];
+    uint8_t head_remainder[0x200];
+    uint8_t tail_remainder[0x200];
     int remainder_len;
     QEMUIOVector iov;
 };
-- 
1.7.10.4