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authorAlex Williamson <alex.williamson@redhat.com>2020-11-02 15:02:00 -0700
committerAlex Williamson <alex.williamson@redhat.com>2020-11-03 11:07:40 -0700
commit38565c93c8a1306dc5f245572a545fbea908ac41 (patch)
tree1411664b0374b6b9726259e95a9f2ca25a0896e7 /drivers/vfio
parent8e91cb3812121aca8369d6c4e717ddd072280d0f (diff)
downloadlinux-38565c93c8a1306dc5f245572a545fbea908ac41.tar.bz2
vfio/pci: Implement ioeventfd thread handler for contended memory lock
The ioeventfd is called under spinlock with interrupts disabled, therefore if the memory lock is contended defer code that might sleep to a thread context. Fixes: bc93b9ae0151 ("vfio-pci: Avoid recursive read-lock usage") Link: https://bugzilla.kernel.org/show_bug.cgi?id=209253#c1 Reported-by: Ian Pilcher <arequipeno@gmail.com> Tested-by: Ian Pilcher <arequipeno@gmail.com> Tested-by: Justin Gatzen <justin.gatzen@gmail.com> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Diffstat (limited to 'drivers/vfio')
-rw-r--r--drivers/vfio/pci/vfio_pci_rdwr.c43
1 files changed, 35 insertions, 8 deletions
diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c b/drivers/vfio/pci/vfio_pci_rdwr.c
index 9e353c484ace..a0b5fc8e46f4 100644
--- a/drivers/vfio/pci/vfio_pci_rdwr.c
+++ b/drivers/vfio/pci/vfio_pci_rdwr.c
@@ -356,34 +356,60 @@ ssize_t vfio_pci_vga_rw(struct vfio_pci_device *vdev, char __user *buf,
return done;
}
-static int vfio_pci_ioeventfd_handler(void *opaque, void *unused)
+static void vfio_pci_ioeventfd_do_write(struct vfio_pci_ioeventfd *ioeventfd,
+ bool test_mem)
{
- struct vfio_pci_ioeventfd *ioeventfd = opaque;
-
switch (ioeventfd->count) {
case 1:
- vfio_pci_iowrite8(ioeventfd->vdev, ioeventfd->test_mem,
+ vfio_pci_iowrite8(ioeventfd->vdev, test_mem,
ioeventfd->data, ioeventfd->addr);
break;
case 2:
- vfio_pci_iowrite16(ioeventfd->vdev, ioeventfd->test_mem,
+ vfio_pci_iowrite16(ioeventfd->vdev, test_mem,
ioeventfd->data, ioeventfd->addr);
break;
case 4:
- vfio_pci_iowrite32(ioeventfd->vdev, ioeventfd->test_mem,
+ vfio_pci_iowrite32(ioeventfd->vdev, test_mem,
ioeventfd->data, ioeventfd->addr);
break;
#ifdef iowrite64
case 8:
- vfio_pci_iowrite64(ioeventfd->vdev, ioeventfd->test_mem,
+ vfio_pci_iowrite64(ioeventfd->vdev, test_mem,
ioeventfd->data, ioeventfd->addr);
break;
#endif
}
+}
+
+static int vfio_pci_ioeventfd_handler(void *opaque, void *unused)
+{
+ struct vfio_pci_ioeventfd *ioeventfd = opaque;
+ struct vfio_pci_device *vdev = ioeventfd->vdev;
+
+ if (ioeventfd->test_mem) {
+ if (!down_read_trylock(&vdev->memory_lock))
+ return 1; /* Lock contended, use thread */
+ if (!__vfio_pci_memory_enabled(vdev)) {
+ up_read(&vdev->memory_lock);
+ return 0;
+ }
+ }
+
+ vfio_pci_ioeventfd_do_write(ioeventfd, false);
+
+ if (ioeventfd->test_mem)
+ up_read(&vdev->memory_lock);
return 0;
}
+static void vfio_pci_ioeventfd_thread(void *opaque, void *unused)
+{
+ struct vfio_pci_ioeventfd *ioeventfd = opaque;
+
+ vfio_pci_ioeventfd_do_write(ioeventfd, ioeventfd->test_mem);
+}
+
long vfio_pci_ioeventfd(struct vfio_pci_device *vdev, loff_t offset,
uint64_t data, int count, int fd)
{
@@ -457,7 +483,8 @@ long vfio_pci_ioeventfd(struct vfio_pci_device *vdev, loff_t offset,
ioeventfd->test_mem = vdev->pdev->resource[bar].flags & IORESOURCE_MEM;
ret = vfio_virqfd_enable(ioeventfd, vfio_pci_ioeventfd_handler,
- NULL, NULL, &ioeventfd->virqfd, fd);
+ vfio_pci_ioeventfd_thread, NULL,
+ &ioeventfd->virqfd, fd);
if (ret) {
kfree(ioeventfd);
goto out_unlock;