git.ipfire.org Git - thirdparty/kernel/stable-queue.git/blob

   1 From ef3bbb2d3a2ef48c5d4280b619a63bf796d613f7 Mon Sep 17 00:00:00 2001
   2 From: Sasha Levin <sashal@kernel.org>
   3 Date: Mon, 2 Nov 2020 15:02:00 -0700
   4 Subject: vfio/pci: Implement ioeventfd thread handler for contended memory
   5  lock
   6
   7 From: Alex Williamson <alex.williamson@redhat.com>
   8
   9 [ Upstream commit 38565c93c8a1306dc5f245572a545fbea908ac41 ]
  10
  11 The ioeventfd is called under spinlock with interrupts disabled,
  12 therefore if the memory lock is contended defer code that might
  13 sleep to a thread context.
  14
  15 Fixes: bc93b9ae0151 ("vfio-pci: Avoid recursive read-lock usage")
  16 Link: https://bugzilla.kernel.org/show_bug.cgi?id=209253#c1
  17 Reported-by: Ian Pilcher <arequipeno@gmail.com>
  18 Tested-by: Ian Pilcher <arequipeno@gmail.com>
  19 Tested-by: Justin Gatzen <justin.gatzen@gmail.com>
  20 Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
  21 Signed-off-by: Sasha Levin <sashal@kernel.org>
  22 ---
  23  drivers/vfio/pci/vfio_pci_rdwr.c | 43 ++++++++++++++++++++++++++------
  24  1 file changed, 35 insertions(+), 8 deletions(-)
  25
  26 diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c b/drivers/vfio/pci/vfio_pci_rdwr.c
  27 index 9e353c484ace2..a0b5fc8e46f4d 100644
  28 --- a/drivers/vfio/pci/vfio_pci_rdwr.c
  29 +++ b/drivers/vfio/pci/vfio_pci_rdwr.c
  30 @@ -356,34 +356,60 @@ ssize_t vfio_pci_vga_rw(struct vfio_pci_device *vdev, char __user *buf,
  31         return done;
  32  }
  33
  34 -static int vfio_pci_ioeventfd_handler(void *opaque, void *unused)
  35 +static void vfio_pci_ioeventfd_do_write(struct vfio_pci_ioeventfd *ioeventfd,
  36 +                                       bool test_mem)
  37  {
  38 -       struct vfio_pci_ioeventfd *ioeventfd = opaque;
  39 -
  40         switch (ioeventfd->count) {
  41         case 1:
  42 -               vfio_pci_iowrite8(ioeventfd->vdev, ioeventfd->test_mem,
  43 +               vfio_pci_iowrite8(ioeventfd->vdev, test_mem,
  44                                   ioeventfd->data, ioeventfd->addr);
  45                 break;
  46         case 2:
  47 -               vfio_pci_iowrite16(ioeventfd->vdev, ioeventfd->test_mem,
  48 +               vfio_pci_iowrite16(ioeventfd->vdev, test_mem,
  49                                    ioeventfd->data, ioeventfd->addr);
  50                 break;
  51         case 4:
  52 -               vfio_pci_iowrite32(ioeventfd->vdev, ioeventfd->test_mem,
  53 +               vfio_pci_iowrite32(ioeventfd->vdev, test_mem,
  54                                    ioeventfd->data, ioeventfd->addr);
  55                 break;
  56  #ifdef iowrite64
  57         case 8:
  58 -               vfio_pci_iowrite64(ioeventfd->vdev, ioeventfd->test_mem,
  59 +               vfio_pci_iowrite64(ioeventfd->vdev, test_mem,
  60                                    ioeventfd->data, ioeventfd->addr);
  61                 break;
  62  #endif
  63         }
  64 +}
  65 +
  66 +static int vfio_pci_ioeventfd_handler(void *opaque, void *unused)
  67 +{
  68 +       struct vfio_pci_ioeventfd *ioeventfd = opaque;
  69 +       struct vfio_pci_device *vdev = ioeventfd->vdev;
  70 +
  71 +       if (ioeventfd->test_mem) {
  72 +               if (!down_read_trylock(&vdev->memory_lock))
  73 +                       return 1; /* Lock contended, use thread */
  74 +               if (!__vfio_pci_memory_enabled(vdev)) {
  75 +                       up_read(&vdev->memory_lock);
  76 +                       return 0;
  77 +               }
  78 +       }
  79 +
  80 +       vfio_pci_ioeventfd_do_write(ioeventfd, false);
  81 +
  82 +       if (ioeventfd->test_mem)
  83 +               up_read(&vdev->memory_lock);
  84
  85         return 0;
  86  }
  87
  88 +static void vfio_pci_ioeventfd_thread(void *opaque, void *unused)
  89 +{
  90 +       struct vfio_pci_ioeventfd *ioeventfd = opaque;
  91 +
  92 +       vfio_pci_ioeventfd_do_write(ioeventfd, ioeventfd->test_mem);
  93 +}
  94 +
  95  long vfio_pci_ioeventfd(struct vfio_pci_device *vdev, loff_t offset,
  96                         uint64_t data, int count, int fd)
  97  {
  98 @@ -457,7 +483,8 @@ long vfio_pci_ioeventfd(struct vfio_pci_device *vdev, loff_t offset,
  99         ioeventfd->test_mem = vdev->pdev->resource[bar].flags & IORESOURCE_MEM;
 100
 101         ret = vfio_virqfd_enable(ioeventfd, vfio_pci_ioeventfd_handler,
 102 -                                NULL, NULL, &ioeventfd->virqfd, fd);
 103 +                                vfio_pci_ioeventfd_thread, NULL,
 104 +                                &ioeventfd->virqfd, fd);
 105         if (ret) {
 106                 kfree(ioeventfd);
 107                 goto out_unlock;
 108 --
 109 2.27.0
 110