[Qemu-devel] [PATCH] dma/rc4030: do multiple calls to address_space_rw when doing DMA transfers

["Hervé Poussineau" <hpoussin@reactos.org>]

This workarounds a bug in memory management.

To reproduce the problem, try to start the Windows NT 4.0/MIPS installer.
After loading some files, you should see a screen saying
"To set up Windows NT now, press ENTER."
However, you're welcomed with an IRQL_NOT_LESS_OR_EQUAL bugcheck or an
Unknown Hard Error c0000221.

Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>
---
 hw/dma/rc4030.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/hw/dma/rc4030.c b/hw/dma/rc4030.c
index 3efa6de..d265d6c 100644
--- a/hw/dma/rc4030.c
+++ b/hw/dma/rc4030.c
@@ -681,6 +681,7 @@ static void rc4030_do_dma(void *opaque, int n, uint8_t *buf, int len, int is_wri
     rc4030State *s = opaque;
     hwaddr dma_addr;
     int dev_to_mem;
+    int i;
 
     s->dma_regs[n][DMA_REG_ENABLE] &= ~(DMA_FLAG_TC_INTR | DMA_FLAG_MEM_INTR | DMA_FLAG_ADDR_INTR);
 
@@ -699,8 +700,22 @@ static void rc4030_do_dma(void *opaque, int n, uint8_t *buf, int len, int is_wri
     dma_addr = s->dma_regs[n][DMA_REG_ADDRESS];
 
     /* Read/write data at right place */
+#if 1 /* workaround for a bug in memory management */
+    for (i = 0; i < len; ) {
+        int ncpy = DMA_PAGESIZE - (dma_addr & (DMA_PAGESIZE - 1));
+        if (ncpy > len - i) {
+            ncpy = len - i;
+        }
+        address_space_rw(&s->dma_as, dma_addr, MEMTXATTRS_UNSPECIFIED,
+                         buf + i, ncpy, is_write);
+
+        dma_addr += ncpy;
+        i += ncpy;
+    }
+#else
     address_space_rw(&s->dma_as, dma_addr, MEMTXATTRS_UNSPECIFIED,
                      buf, len, is_write);
+#endif
 
     s->dma_regs[n][DMA_REG_ENABLE] |= DMA_FLAG_TC_INTR;
     s->dma_regs[n][DMA_REG_COUNT] -= len;
-- 
2.1.4