qtest/ahci: add fragmented dma test

Test what happens when we try to use extremely short PRDTs
to accomplish a small data transfer.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-id: 1424905602-24715-7-git-send-email-jsnow@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

tests/ahci-test.c

@@ -851,6 +851,63 @@ static void test_identify(void)
     ahci_shutdown(ahci);
 }
 
+/**
+ * Fragmented DMA test: Perform a standard 4K DMA read/write
+ * test, but make sure the physical regions are fragmented to
+ * be very small, each just 32 bytes, to see how AHCI performs
+ * with chunks defined to be much less than a sector.
+ */
+static void test_dma_fragmented(void)
+{
+    AHCIQState *ahci;
+    AHCICommand *cmd;
+    uint8_t px;
+    size_t bufsize = 4096;
+    unsigned char *tx = g_malloc(bufsize);
+    unsigned char *rx = g_malloc0(bufsize);
+    unsigned i;
+    uint64_t ptr;
+
+    ahci = ahci_boot_and_enable();
+    px = ahci_port_select(ahci);
+    ahci_port_clear(ahci, px);
+
+    /* create pattern */
+    for (i = 0; i < bufsize; i++) {
+        tx[i] = (bufsize - i);
+    }
+
+    /* Create a DMA buffer in guest memory, and write our pattern to it. */
+    ptr = guest_alloc(ahci->parent->alloc, bufsize);
+    g_assert(ptr);
+    memwrite(ptr, tx, bufsize);
+
+    cmd = ahci_command_create(CMD_WRITE_DMA);
+    ahci_command_adjust(cmd, 0, ptr, bufsize, 32);
+    ahci_command_commit(ahci, cmd, px);
+    ahci_command_issue(ahci, cmd);
+    ahci_command_verify(ahci, cmd);
+    g_free(cmd);
+
+    cmd = ahci_command_create(CMD_READ_DMA);
+    ahci_command_adjust(cmd, 0, ptr, bufsize, 32);
+    ahci_command_commit(ahci, cmd, px);
+    ahci_command_issue(ahci, cmd);
+    ahci_command_verify(ahci, cmd);
+    g_free(cmd);
+
+    /* Read back the guest's receive buffer into local memory */
+    memread(ptr, rx, bufsize);
+    guest_free(ahci->parent->alloc, ptr);
+
+    g_assert_cmphex(memcmp(tx, rx, bufsize), ==, 0);
+
+    ahci_shutdown(ahci);
+
+    g_free(rx);
+    g_free(tx);
+}
+
 /******************************************************************************/
 /* AHCI I/O Test Matrix Definitions                                           */
 
@@ -1054,6 +1111,8 @@ int main(int argc, char **argv)
         }
     }
 
+    qtest_add_func("/ahci/io/dma/lba28/fragmented", test_dma_fragmented);
+
     ret = g_test_run();
 
     /* Cleanup */