[Qemu-devel] [PATCH v2 2/2] ide-test: Check what happens with bus mastering disabled

[Kevin Wolf <kwolf@redhat.com>]

The main goal is that qemu doesn't crash.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 tests/ide-test.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/tests/ide-test.c b/tests/ide-test.c
index 7307f1d..bc824a8 100644
--- a/tests/ide-test.c
+++ b/tests/ide-test.c
@@ -81,6 +81,7 @@ enum {
     CMD_IDENTIFY    = 0xec,
 
     CMDF_ABORT      = 0x100,
+    CMDF_NO_BM      = 0x200,
 };
 
 enum {
@@ -192,6 +193,11 @@ static int send_dma_request(int cmd, uint64_t sector, int nb_sectors,
         g_assert_not_reached();
     }
 
+    if (flags & CMDF_NO_BM) {
+        qpci_config_writew(dev, PCI_COMMAND,
+                           PCI_COMMAND_IO | PCI_COMMAND_MEMORY);
+    }
+
     /* Select device 0 */
     outb(IDE_BASE + reg_device, 0 | LBA);
 
@@ -352,6 +358,25 @@ static void test_bmdma_long_prdt(void)
     assert_bit_clear(inb(IDE_BASE + reg_status), DF | ERR);
 }
 
+static void test_bmdma_no_busmaster(void)
+{
+    uint8_t status;
+
+    /* No PRDT_EOT, each entry addr 0/size 64k, and in theory qemu shouldn't be
+     * able to access it anyway because the Bus Master bit in the PCI command
+     * register isn't set. This is complete nonsense, but it used to be pretty
+     * good at confusing and occasionally crashing qemu. */
+    PrdtEntry prdt[4096] = { };
+
+    status = send_dma_request(CMD_READ_DMA | CMDF_NO_BM, 0, 512,
+                              prdt, ARRAY_SIZE(prdt));
+
+    /* Not entirely clear what the expected result is, but this is what we get
+     * in practice. At least we want to be aware of any changes. */
+    g_assert_cmphex(status, ==, BM_STS_ACTIVE | BM_STS_INTR);
+    assert_bit_clear(inb(IDE_BASE + reg_status), DF | ERR);
+}
+
 static void test_bmdma_setup(void)
 {
     ide_test_start(
@@ -493,6 +518,7 @@ int main(int argc, char **argv)
     qtest_add_func("/ide/bmdma/simple_rw", test_bmdma_simple_rw);
     qtest_add_func("/ide/bmdma/short_prdt", test_bmdma_short_prdt);
     qtest_add_func("/ide/bmdma/long_prdt", test_bmdma_long_prdt);
+    qtest_add_func("/ide/bmdma/no_busmaster", test_bmdma_no_busmaster);
     qtest_add_func("/ide/bmdma/teardown", test_bmdma_teardown);
 
     qtest_add_func("/ide/flush", test_flush);
-- 
1.8.1.4