[Qemu-devel] [PATCH] RFC: hcd-ohci: add dma error handling

[Alexey Kardashevskiy <aik@ozlabs.ru>]

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Current hcd-ohci does not handle DMA errors which can actually
happen.

However it is not clear what approach should be used here -
for example, get_dwords returns positive number saying that there
is no error as all the callers consider the return value as fail
if it is less than zero. Normally you would expect bool=true/int=0
as success and bool=false/int=-1 as fail.

Any suggestion?

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 hw/usb/hcd-ohci.c | 77 +++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 52 insertions(+), 25 deletions(-)

diff --git a/hw/usb/hcd-ohci.c b/hw/usb/hcd-ohci.c
index a096ecf..48297da 100644
--- a/hw/usb/hcd-ohci.c
+++ b/hw/usb/hcd-ohci.c
@@ -508,7 +508,9 @@ static inline int get_dwords(OHCIState *ohci,
     addr += ohci->localmem_base;
 
     for (i = 0; i < num; i++, buf++, addr += sizeof(*buf)) {
-        dma_memory_read(ohci->as, addr, buf, sizeof(*buf));
+        if (dma_memory_read(ohci->as, addr, buf, sizeof(*buf))) {
+            return -1;
+        }
         *buf = le32_to_cpu(*buf);
     }
 
@@ -525,7 +527,9 @@ static inline int put_dwords(OHCIState *ohci,
 
     for (i = 0; i < num; i++, buf++, addr += sizeof(*buf)) {
         uint32_t tmp = cpu_to_le32(*buf);
-        dma_memory_write(ohci->as, addr, &tmp, sizeof(tmp));
+        if (dma_memory_write(ohci->as, addr, &tmp, sizeof(tmp))) {
+            return -1;
+        }
     }
 
     return 1;
@@ -540,7 +544,9 @@ static inline int get_words(OHCIState *ohci,
     addr += ohci->localmem_base;
 
     for (i = 0; i < num; i++, buf++, addr += sizeof(*buf)) {
-        dma_memory_read(ohci->as, addr, buf, sizeof(*buf));
+        if (dma_memory_read(ohci->as, addr, buf, sizeof(*buf))) {
+            return -1;
+        }
         *buf = le16_to_cpu(*buf);
     }
 
@@ -557,7 +563,9 @@ static inline int put_words(OHCIState *ohci,
 
     for (i = 0; i < num; i++, buf++, addr += sizeof(*buf)) {
         uint16_t tmp = cpu_to_le16(*buf);
-        dma_memory_write(ohci->as, addr, &tmp, sizeof(tmp));
+        if (dma_memory_write(ohci->as, addr, &tmp, sizeof(tmp))) {
+            return -1;
+        }
     }
 
     return 1;
@@ -585,8 +593,8 @@ static inline int ohci_read_iso_td(OHCIState *ohci,
 static inline int ohci_read_hcca(OHCIState *ohci,
                                  dma_addr_t addr, struct ohci_hcca *hcca)
 {
-    dma_memory_read(ohci->as, addr + ohci->localmem_base, hcca, sizeof(*hcca));
-    return 1;
+    return dma_memory_read(ohci->as, addr + ohci->localmem_base,
+                           hcca, sizeof(*hcca)) ? -1 : 0;
 }
 
 static inline int ohci_put_ed(OHCIState *ohci,
@@ -617,16 +625,15 @@ static inline int ohci_put_iso_td(OHCIState *ohci,
 static inline int ohci_put_hcca(OHCIState *ohci,
                                 dma_addr_t addr, struct ohci_hcca *hcca)
 {
-    dma_memory_write(ohci->as,
-                     addr + ohci->localmem_base + HCCA_WRITEBACK_OFFSET,
-                     (char *)hcca + HCCA_WRITEBACK_OFFSET,
-                     HCCA_WRITEBACK_SIZE);
-    return 1;
+    return dma_memory_write(ohci->as,
+                            addr + ohci->localmem_base + HCCA_WRITEBACK_OFFSET,
+                            (char *)hcca + HCCA_WRITEBACK_OFFSET,
+                            HCCA_WRITEBACK_SIZE) ? -1 : 0;
 }
 
 /* Read/Write the contents of a TD from/to main memory.  */
-static void ohci_copy_td(OHCIState *ohci, struct ohci_td *td,
-                         uint8_t *buf, int len, DMADirection dir)
+static int ohci_copy_td(OHCIState *ohci, struct ohci_td *td,
+                        uint8_t *buf, int len, DMADirection dir)
 {
     dma_addr_t ptr, n;
 
@@ -634,18 +641,26 @@ static void ohci_copy_td(OHCIState *ohci, struct ohci_td *td,
     n = 0x1000 - (ptr & 0xfff);
     if (n > len)
         n = len;
-    dma_memory_rw(ohci->as, ptr + ohci->localmem_base, buf, n, dir);
-    if (n == len)
-        return;
+
+    if (dma_memory_rw(ohci->as, ptr + ohci->localmem_base, buf, n, dir)) {
+        return -1;
+    }
+    if (n == len) {
+        return 0;
+    }
     ptr = td->be & ~0xfffu;
     buf += n;
-    dma_memory_rw(ohci->as, ptr + ohci->localmem_base, buf, len - n, dir);
+    if (dma_memory_rw(ohci->as, ptr + ohci->localmem_base, buf,
+                      len - n, dir)) {
+        return -1;
+    }
+    return 0;
 }
 
 /* Read/Write the contents of an ISO TD from/to main memory.  */
-static void ohci_copy_iso_td(OHCIState *ohci,
-                             uint32_t start_addr, uint32_t end_addr,
-                             uint8_t *buf, int len, DMADirection dir)
+static int ohci_copy_iso_td(OHCIState *ohci,
+                            uint32_t start_addr, uint32_t end_addr,
+                            uint8_t *buf, int len, DMADirection dir)
 {
     dma_addr_t ptr, n;
 
@@ -653,12 +668,20 @@ static void ohci_copy_iso_td(OHCIState *ohci,
     n = 0x1000 - (ptr & 0xfff);
     if (n > len)
         n = len;
-    dma_memory_rw(ohci->as, ptr + ohci->localmem_base, buf, n, dir);
-    if (n == len)
-        return;
+
+    if (dma_memory_rw(ohci->as, ptr + ohci->localmem_base, buf, n, dir)) {
+        return -1;
+    }
+    if (n == len) {
+        return 0;
+    }
     ptr = end_addr & ~0xfffu;
     buf += n;
-    dma_memory_rw(ohci->as, ptr + ohci->localmem_base, buf, len - n, dir);
+    if (dma_memory_rw(ohci->as, ptr + ohci->localmem_base, buf,
+                      len - n, dir)) {
+        return -1;
+    }
+    return 0;
 }
 
 static void ohci_process_lists(OHCIState *ohci, int completion);
@@ -1236,7 +1259,11 @@ static void ohci_frame_boundary(void *opaque)
     OHCIState *ohci = opaque;
     struct ohci_hcca hcca;
 
-    ohci_read_hcca(ohci, ohci->hcca, &hcca);
+    if (ohci_read_hcca(ohci, ohci->hcca, &hcca)) {
+        fprintf(stderr, "usb-ohci: HCCA read error at %x\n", ohci->hcca);
+        /* TODO: Add signaling of DMA errors to the guest */
+        return;
+    }
 
     /* Process all the lists at the end of the frame */
     if (ohci->ctl & OHCI_CTL_PLE) {
-- 
1.8.3.2