[PATCH v8] virtio-pci: fix use of a released vector

[Michael S. Tsirkin]

From: Cindy Lu <lulu@redhat.com>

During the booting process of the non-standard image, the behavior of the
called function in qemu is as follows:

1. vhost_net_stop() was triggered by guest image. This will call the function
virtio_pci_set_guest_notifiers() with assgin= false,
virtio_pci_set_guest_notifiers(） will release the irqfd for vector 0

2. virtio_reset() was triggered, this will set configure vector to 
VIRTIO_NO_VECTOR

3.vhost_net_start() was called (at this time, the configure vector is
still VIRTIO_NO_VECTOR) and then call virtio_pci_set_guest_notifiers() with
assgin=true, so the irqfd for vector 0 is still not "init" during this process

4. The system continues to boot and sets the vector back to 0. After that
msix_fire_vector_notifier() was triggered to unmask the vector 0 and  meet the 
crash

To fix the issue, we need to support changing the vector after 
VIRTIO_CONFIG_S_DRIVER_OK is set.

(gdb) bt
0  __pthread_kill_implementation (threadid=<optimized out>, 
signo=signo@entry=6, no_tid=no_tid@entry=0)
    at pthread_kill.c:44
1  0x00007fc87148ec53 in __pthread_kill_internal (signo=6, threadid=<optimized 
out>) at pthread_kill.c:78
2  0x00007fc87143e956 in __GI_raise (sig=sig@entry=6) at 
../sysdeps/posix/raise.c:26
3  0x00007fc8714287f4 in __GI_abort () at abort.c:79
4  0x00007fc87142871b in __assert_fail_base
    (fmt=0x7fc8715bbde0 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", 
assertion=0x5606413efd53 "ret == 0", file=0x5606413ef87d 
"../accel/kvm/kvm-all.c", line=1837, function=<optimized out>) at assert.c:92
5  0x00007fc871437536 in __GI___assert_fail
    (assertion=0x5606413efd53 "ret == 0", file=0x5606413ef87d 
"../accel/kvm/kvm-all.c", line=1837, function=0x5606413f06f0 
<__PRETTY_FUNCTION__.19> "kvm_irqchip_commit_routes") at assert.c:101
6  0x0000560640f884b5 in kvm_irqchip_commit_routes (s=0x560642cae1f0) at 
../accel/kvm/kvm-all.c:1837
7  0x0000560640c98f8e in virtio_pci_one_vector_unmask
    (proxy=0x560643c65f00, queue_no=4294967295, vector=0, msg=..., 
n=0x560643c6e4c8)
    at ../hw/virtio/virtio-pci.c:1005
8  0x0000560640c99201 in virtio_pci_vector_unmask (dev=0x560643c65f00, 
vector=0, msg=...)
    at ../hw/virtio/virtio-pci.c:1070
9  0x0000560640bc402e in msix_fire_vector_notifier (dev=0x560643c65f00, 
vector=0, is_masked=false)
    at ../hw/pci/msix.c:120
10 0x0000560640bc40f1 in msix_handle_mask_update (dev=0x560643c65f00, vector=0, 
was_masked=true)
    at ../hw/pci/msix.c:140
11 0x0000560640bc4503 in msix_table_mmio_write (opaque=0x560643c65f00, addr=12, 
val=0, size=4)
    at ../hw/pci/msix.c:231
12 0x0000560640f26d83 in memory_region_write_accessor
    (mr=0x560643c66540, addr=12, value=0x7fc86b7bc628, size=4, shift=0, 
mask=4294967295, attrs=...)
    at ../system/memory.c:497
13 0x0000560640f270a6 in access_with_adjusted_size

     (addr=12, value=0x7fc86b7bc628, size=4, access_size_min=1, 
access_size_max=4, access_fn=0x560640f26c8d <memory_region_write_accessor>, 
mr=0x560643c66540, attrs=...) at ../system/memory.c:573
14 0x0000560640f2a2b5 in memory_region_dispatch_write (mr=0x560643c66540, 
addr=12, data=0, op=MO_32, attrs=...)
    at ../system/memory.c:1521
15 0x0000560640f37bac in flatview_write_continue
    (fv=0x7fc65805e0b0, addr=4273803276, attrs=..., ptr=0x7fc871e9c028, len=4, 
addr1=12, l=4, mr=0x560643c66540)
    at ../system/physmem.c:2714
16 0x0000560640f37d0f in flatview_write
    (fv=0x7fc65805e0b0, addr=4273803276, attrs=..., buf=0x7fc871e9c028, len=4) 
at ../system/physmem.c:2756
17 0x0000560640f380bf in address_space_write
    (as=0x560642161ae0 <address_space_memory>, addr=4273803276, attrs=..., 
buf=0x7fc871e9c028, len=4)
    at ../system/physmem.c:2863
18 0x0000560640f3812c in address_space_rw
    (as=0x560642161ae0 <address_space_memory>, addr=4273803276, attrs=..., 
buf=0x7fc871e9c028, len=4, is_write=true) at ../system/physmem.c:2873
--Type <RET> for more, q to quit, c to continue without paging--
19 0x0000560640f8aa55 in kvm_cpu_exec (cpu=0x560642f205e0) at 
../accel/kvm/kvm-all.c:2915
20 0x0000560640f8d731 in kvm_vcpu_thread_fn (arg=0x560642f205e0) at 
../accel/kvm/kvm-accel-ops.c:51
21 0x00005606411949f4 in qemu_thread_start (args=0x560642f292b0) at 
../util/qemu-thread-posix.c:541
22 0x00007fc87148cdcd in start_thread (arg=<optimized out>) at 
pthread_create.c:442
23 0x00007fc871512630 in clone3 () at 
../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
(gdb)

MST: coding style and typo fixups

Fixes: f9a09ca3ea ("vhost: add support for configure interrupt")
Cc: qemu-stable@nongnu.org
Signed-off-by: Cindy Lu <lulu@redhat.com>
Message-Id: <20240412062750.475180-1-lulu@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/virtio/virtio-pci.c | 37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

v7->v8:
more cleanups, suggested by Philip

still untested, i just got involved to help address coding style
issues

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index cb6940fc0e..cb159fd078 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1424,6 +1424,38 @@ static int virtio_pci_add_mem_cap(VirtIOPCIProxy *proxy,
     return offset;
 }
 
+static void virtio_pci_set_vector(VirtIODevice *vdev,
+                                  VirtIOPCIProxy *proxy,
+                                  int queue_no, uint16_t old_vector,
+                                  uint16_t new_vector)
+{
+    bool kvm_irqfd = (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
+        msix_enabled(&proxy->pci_dev) && kvm_msi_via_irqfd_enabled();
+
+    if (new_vector == old_vector) {
+        return;
+    }
+
+    /*
+     * If the device uses irqfd and the vector changes after DRIVER_OK is
+     * set, we need to release the old vector and set up the new one.
+     * Otherwise just need to set the new vector on the device.
+     */
+    if (kvm_irqfd && old_vector != VIRTIO_NO_VECTOR) {
+        kvm_virtio_pci_vector_release_one(proxy, queue_no);
+    }
+    /* Set the new vector on the device. */
+    if (queue_no == VIRTIO_CONFIG_IRQ_IDX) {
+        vdev->config_vector = new_vector;
+    } else {
+        virtio_queue_set_vector(vdev, queue_no, new_vector);
+    }
+    /* If the new vector changed need to set it up. */
+    if (kvm_irqfd && new_vector != VIRTIO_NO_VECTOR) {
+        kvm_virtio_pci_vector_use_one(proxy, queue_no);
+    }
+}
+
 int virtio_pci_add_shm_cap(VirtIOPCIProxy *proxy,
                            uint8_t bar, uint64_t offset, uint64_t length,
                            uint8_t id)
@@ -1570,7 +1602,8 @@ static void virtio_pci_common_write(void *opaque, hwaddr 
addr,
         } else {
             val = VIRTIO_NO_VECTOR;
         }
-        vdev->config_vector = val;
+        virtio_pci_set_vector(vdev, proxy, VIRTIO_CONFIG_IRQ_IDX,
+                              vdev->config_vector, val);
         break;
     case VIRTIO_PCI_COMMON_STATUS:
         if (!(val & VIRTIO_CONFIG_S_DRIVER_OK)) {
@@ -1610,7 +1643,7 @@ static void virtio_pci_common_write(void *opaque, hwaddr 
addr,
         } else {
             val = VIRTIO_NO_VECTOR;
         }
-        virtio_queue_set_vector(vdev, vdev->queue_sel, val);
+        virtio_pci_set_vector(vdev, proxy, vdev->queue_sel, vector, val);
         break;
     case VIRTIO_PCI_COMMON_Q_ENABLE:
         if (val == 1) {
-- 
MST