From: Alex Williamson alex.williamson@redhat.com
[ Upstream commit 38565c93c8a1306dc5f245572a545fbea908ac41 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/vfio/pci/vfio_pci_rdwr.c | 43 ++++++++++++++++++++++++++------ 1 file changed, 35 insertions(+), 8 deletions(-)
diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c b/drivers/vfio/pci/vfio_pci_rdwr.c index 9e353c484ace2..a0b5fc8e46f4d 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;