[PULL 8/8] tests/qtest/ahci: regression test for ATAPI read vs. drain

["Denis V. Lunev" <den@openvz.org>]

Add /ahci/cdrom/drain/{pio,dma}: issue a multi-sector ATAPI read whose
byte-count limit spans two sectors so the device must rebuffer in the
middle of the DRQ burst, hold the backend read in flight with a
blkdebug delay, and fire x-blockdev-set-iothread -- which runs
bdrv_drain_all_begin() exactly like a guest reset does through
virtio_blk_stop_ioeventfd().

On the unfixed PIO path the nested sector fetch is queued behind the
drain and the main loop wedges, so the test hangs. The DMA variant
never rebuffers and serves as a sanity twin.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Philippe Mathieu-Daudé <philmd@oss.qualcomm.com>
---
 tests/qtest/ahci-test.c | 66 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/tests/qtest/ahci-test.c b/tests/qtest/ahci-test.c
index 58bc04b3ef..71d23fe56a 100644
--- a/tests/qtest/ahci-test.c
+++ b/tests/qtest/ahci-test.c
@@ -1754,6 +1754,70 @@ static void test_atapi_engine_restart_dma(void)
     test_atapi_engine_restart_in_flight(true);
 }
 
+/*
+ * Regression test: a multi-sector ATAPI read fetches its later sectors from
+ * inside the first read's completion; a concurrent drain (as a guest reset
+ * triggers via bdrv_drain_all_begin) must not wedge on that nested read.
+ * blkdebug keeps the read in flight across x-blockdev-set-iothread.
+ */
+static void test_atapi_drain_in_flight(bool dma)
+{
+    AHCIQState *ahci;
+    AHCICommand *cmd;
+    unsigned char *tx;
+    char *iso;
+    int fd;
+    uint8_t port;
+    uint64_t buffer;
+    uint16_t bcl = ATAPI_SECTOR_SIZE * 2;
+    uint64_t iso_size = (uint64_t)ATAPI_SECTOR_SIZE * 3;
+
+    fd = prepare_iso(iso_size, &tx, &iso);
+
+    /* 1s read delay: a wide margin so the drain starts before it completes */
+    ahci = ahci_boot_and_enable(
+        "-blockdev driver=file,node-name=file0,filename=%s,read-only=on "
+        "-blockdev driver=blkdebug,node-name=cd0,image=file0,read-only=on,"
+        "inject-error.0.event=none,inject-error.0.iotype=read,"
+        "inject-error.0.errno=0,inject-error.0.delay-ns=1000000000 "
+        "-M q35 "
+        "-device ide-cd,drive=cd0 ", iso);
+    port = ahci_port_select(ahci);
+
+    buffer = ahci_alloc(ahci, bcl);
+    qtest_memset(ahci->parent->qts, buffer, 0x00, bcl);
+
+    cmd = ahci_atapi_command_create(CMD_ATAPI_READ_10, bcl, dma);
+    ahci_command_adjust(cmd, 0, buffer, bcl, 0);
+    ahci_command_commit(ahci, cmd, port);
+    ahci_command_issue_async(ahci, cmd);
+
+    /* Drain (all nodes) while the delayed read is still in flight. */
+    qtest_qmp_assert_success(ahci->parent->qts,
+        "{ 'execute': 'x-blockdev-set-iothread',"
+        "  'arguments': { 'node-name': 'cd0', 'iothread': null,"
+        "                 'force': true } }");
+
+    /* Round-trip through the device to confirm qemu is still alive. */
+    ahci_px_rreg(ahci, port, AHCI_PX_TFD);
+
+    ahci_command_free(cmd);
+    ahci_free(ahci, buffer);
+    g_free(tx);
+    ahci_shutdown(ahci);
+    remove_iso(fd, iso);
+}
+
+static void test_atapi_drain_pio(void)
+{
+    test_atapi_drain_in_flight(false);
+}
+
+static void test_atapi_drain_dma(void)
+{
+    test_atapi_drain_in_flight(true);
+}
+
 /* Regression test: Test that a READ_CD command with a BCL of 0 but a size of 0
  * completes as a NOP instead of erroring out. */
 static void test_atapi_bcl(void)
@@ -2177,6 +2241,8 @@ int main(int argc, char **argv)
                    test_atapi_engine_restart_pio);
     qtest_add_func("/ahci/cdrom/engine_restart/dma",
                    test_atapi_engine_restart_dma);
+    qtest_add_func("/ahci/cdrom/drain/pio", test_atapi_drain_pio);
+    qtest_add_func("/ahci/cdrom/drain/dma", test_atapi_drain_dma);
 
     ret = g_test_run();
 
-- 
2.53.0