diff options
| author | Alex Williamson <alex.williamson@redhat.com> | 2020-11-02 15:02:00 -0700 |
|---|---|---|
| committer | Alex Williamson <alex.williamson@redhat.com> | 2020-11-03 11:07:40 -0700 |
| commit | 38565c93c8a1306dc5f245572a545fbea908ac41 (patch) | |
| tree | 1411664b0374b6b9726259e95a9f2ca25a0896e7 /drivers/vfio | |
| parent | 8e91cb3812121aca8369d6c4e717ddd072280d0f (diff) | |
| download | linux-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.c | 43 |
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; |