| Message ID | CANq1E4QmEMMJ+NCeC7ZUhJkcn3v20=Wdf-JrMge2ajk88QQ7NQ@mail.gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Dec 10, 2015 at 11:28:58AM +0100, David Herrmann wrote: > Hi > > On Mon, Nov 30, 2015 at 3:17 AM, Kirill A. Shutemov > <kirill@shutemov.name> wrote: > > There are few defects in vga_get() related to signal hadning: > > > > - we shouldn't check for pending signals for TASK_UNINTERRUPTIBLE > > case; > > > > - if we found pending signal we must remove ourself from wait queue > > and change task state back to running; > > > > - -ERESTARTSYS is more appropriate, I guess. > > > > Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name> > > --- > > > > Alex, I try to get KVM with VGA passthrough working properly. I have i915 > > (HD 4600) on the host and GTX 580 for the guest. The guest GPU is not > > capabale of EFI, so I have to use x-vga=on. It's kinda work with your > > patch for i915.enable_hd_vgaarb=1. But guest refuse to initialize the GPU > > after KVM was not shut down correctly, resulting in host crash like this: > > > > BUG: unable to handle kernel paging request at ffff880870187ed8 > > IP: [<ffff880870187ed8>] 0xffff880870187ed8 > > PGD 2129067 PUD 80000008400001e3 > > Oops: 0011 [#1] PREEMPT SMP > > Modules linked in: iwlmvm iwlwifi > > CPU: 6 PID: 3983 Comm: qemu-system-x86 Not tainted 4.3.0-gentoo #6 > > Hardware name: Gigabyte Technology Co., Ltd. Z87X-UD7 TH/Z87X-UD7 TH-CF, BIOS F5a 06/12/2014 > > task: ffff88087a910000 ti: ffff8808632c0000 task.ti: ffff8808632c0000 > > RIP: 0010:[<ffff880870187ed8>] [<ffff880870187ed8>] 0xffff880870187ed8 > > RSP: 0018:ffff8808632c3d08 EFLAGS: 00010006 > > RAX: ffff880870187db0 RBX: 0000000070187f58 RCX: 0000000000000000 > > RDX: 0000000000000000 RSI: 0000000000000003 RDI: ffff880870187db0 > > RBP: ffff8808632c3d48 R08: 0000000000000000 R09: 0000000000000000 > > R10: 00000000000103c0 R11: 0000000000000293 R12: ffffffff81ea03c8 > > R13: ffffffff8104c7cb R14: 0000000000000000 R15: 0000000000000003 > > FS: 00007f984f9b2700(0000) GS:ffff88089f380000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: ffff880870187ed8 CR3: 00000008645f8000 CR4: 00000000001426e0 > > Stack: > > ffffffff810cc83d 00000000632c3d28 0000000000000000 ffffffff81ea03c0 > > 0000000000000046 0000000000000003 0000000000000000 0000000000000000 > > ffff8808632c3d80 ffffffff810cca44 ffff88087af63800 0000000000000286 > > Call Trace: > > [<ffffffff810cc83d>] ? __wake_up_common+0x4d/0x80 > > [<ffffffff810cca44>] __wake_up+0x34/0x50 > > [<ffffffff815d99e3>] __vga_put+0x73/0xd0 > > [<ffffffff815d9db4>] vga_put+0x54/0x80 > > [<ffffffff8169d042>] vfio_pci_vga_rw+0x1d2/0x220 > > [<ffffffff8169a7f3>] vfio_pci_rw+0x33/0x60 > > [<ffffffff8169abf7>] vfio_pci_write+0x17/0x20 > > [<ffffffff816966a6>] vfio_device_fops_write+0x26/0x30 > > [<ffffffff811a4b23>] __vfs_write+0x23/0xe0 > > [<ffffffff811a4a53>] ? __vfs_read+0x23/0xd0 > > [<ffffffff811b6e35>] ? do_vfs_ioctl+0x2b5/0x490 > > [<ffffffff811a5194>] vfs_write+0xa4/0x190 > > [<ffffffff811a5fa6>] SyS_pwrite64+0x66/0xa0 > > [<ffffffff819a17d7>] entry_SYSCALL_64_fastpath+0x12/0x6a > > Code: 88 ff ff e0 7e 18 70 08 88 ff ff 00 8c 57 76 08 88 ff ff 20 7f 18 70 08 88 ff ff 08 7f 18 70 08 88 ff ff 94 51 1a 81 ff ff ff ff <09> 00 00 00 00 00 00 00 01 8c 57 76 08 88 ff ff 00 8c 57 76 08 > > RIP [<ffff880870187ed8>] 0xffff880870187ed8 > > RSP <ffff8808632c3d08> > > CR2: ffff880870187ed8 > > > > The patch fixes the crash, but doesn't help with getting GPU in guest > > working again. > > > > Any ideas? > > > > --- > > drivers/gpu/vga/vgaarb.c | 6 ++++-- > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c > > index 3166e4bc4eb6..9abcaa53bd25 100644 > > --- a/drivers/gpu/vga/vgaarb.c > > +++ b/drivers/gpu/vga/vgaarb.c > > @@ -395,8 +395,10 @@ int vga_get(struct pci_dev *pdev, unsigned int rsrc, int interruptible) > > set_current_state(interruptible ? > > TASK_INTERRUPTIBLE : > > TASK_UNINTERRUPTIBLE); > > - if (signal_pending(current)) { > > - rc = -EINTR; > > + if (interruptible && signal_pending(current)) { > > + __set_current_state(TASK_RUNNING); > > + remove_wait_queue(&vga_wait_queue, &wait); > > + rc = -ERESTARTSYS; > > break; > > All 3 points are valid, and the patch looks good to me: > > Reviewed-by: David Herrmann <dh.herrmann@gmail.com> > > However, there seems to be a race between vga_lock and putting the > thread asleep. I'm not sure I understand the race you're talking about. Could you elaborate?
Hi On Mon, Dec 14, 2015 at 9:19 AM, Kirill A. Shutemov <kirill@shutemov.name> wrote: > On Thu, Dec 10, 2015 at 11:28:58AM +0100, David Herrmann wrote: >> Hi >> >> On Mon, Nov 30, 2015 at 3:17 AM, Kirill A. Shutemov >> <kirill@shutemov.name> wrote: >> > There are few defects in vga_get() related to signal hadning: >> > >> > - we shouldn't check for pending signals for TASK_UNINTERRUPTIBLE >> > case; >> > >> > - if we found pending signal we must remove ourself from wait queue >> > and change task state back to running; >> > >> > - -ERESTARTSYS is more appropriate, I guess. >> > >> > Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name> >> > --- >> > >> > Alex, I try to get KVM with VGA passthrough working properly. I have i915 >> > (HD 4600) on the host and GTX 580 for the guest. The guest GPU is not >> > capabale of EFI, so I have to use x-vga=on. It's kinda work with your >> > patch for i915.enable_hd_vgaarb=1. But guest refuse to initialize the GPU >> > after KVM was not shut down correctly, resulting in host crash like this: >> > >> > BUG: unable to handle kernel paging request at ffff880870187ed8 >> > IP: [<ffff880870187ed8>] 0xffff880870187ed8 >> > PGD 2129067 PUD 80000008400001e3 >> > Oops: 0011 [#1] PREEMPT SMP >> > Modules linked in: iwlmvm iwlwifi >> > CPU: 6 PID: 3983 Comm: qemu-system-x86 Not tainted 4.3.0-gentoo #6 >> > Hardware name: Gigabyte Technology Co., Ltd. Z87X-UD7 TH/Z87X-UD7 TH-CF, BIOS F5a 06/12/2014 >> > task: ffff88087a910000 ti: ffff8808632c0000 task.ti: ffff8808632c0000 >> > RIP: 0010:[<ffff880870187ed8>] [<ffff880870187ed8>] 0xffff880870187ed8 >> > RSP: 0018:ffff8808632c3d08 EFLAGS: 00010006 >> > RAX: ffff880870187db0 RBX: 0000000070187f58 RCX: 0000000000000000 >> > RDX: 0000000000000000 RSI: 0000000000000003 RDI: ffff880870187db0 >> > RBP: ffff8808632c3d48 R08: 0000000000000000 R09: 0000000000000000 >> > R10: 00000000000103c0 R11: 0000000000000293 R12: ffffffff81ea03c8 >> > R13: ffffffff8104c7cb R14: 0000000000000000 R15: 0000000000000003 >> > FS: 00007f984f9b2700(0000) GS:ffff88089f380000(0000) knlGS:0000000000000000 >> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> > CR2: ffff880870187ed8 CR3: 00000008645f8000 CR4: 00000000001426e0 >> > Stack: >> > ffffffff810cc83d 00000000632c3d28 0000000000000000 ffffffff81ea03c0 >> > 0000000000000046 0000000000000003 0000000000000000 0000000000000000 >> > ffff8808632c3d80 ffffffff810cca44 ffff88087af63800 0000000000000286 >> > Call Trace: >> > [<ffffffff810cc83d>] ? __wake_up_common+0x4d/0x80 >> > [<ffffffff810cca44>] __wake_up+0x34/0x50 >> > [<ffffffff815d99e3>] __vga_put+0x73/0xd0 >> > [<ffffffff815d9db4>] vga_put+0x54/0x80 >> > [<ffffffff8169d042>] vfio_pci_vga_rw+0x1d2/0x220 >> > [<ffffffff8169a7f3>] vfio_pci_rw+0x33/0x60 >> > [<ffffffff8169abf7>] vfio_pci_write+0x17/0x20 >> > [<ffffffff816966a6>] vfio_device_fops_write+0x26/0x30 >> > [<ffffffff811a4b23>] __vfs_write+0x23/0xe0 >> > [<ffffffff811a4a53>] ? __vfs_read+0x23/0xd0 >> > [<ffffffff811b6e35>] ? do_vfs_ioctl+0x2b5/0x490 >> > [<ffffffff811a5194>] vfs_write+0xa4/0x190 >> > [<ffffffff811a5fa6>] SyS_pwrite64+0x66/0xa0 >> > [<ffffffff819a17d7>] entry_SYSCALL_64_fastpath+0x12/0x6a >> > Code: 88 ff ff e0 7e 18 70 08 88 ff ff 00 8c 57 76 08 88 ff ff 20 7f 18 70 08 88 ff ff 08 7f 18 70 08 88 ff ff 94 51 1a 81 ff ff ff ff <09> 00 00 00 00 00 00 00 01 8c 57 76 08 88 ff ff 00 8c 57 76 08 >> > RIP [<ffff880870187ed8>] 0xffff880870187ed8 >> > RSP <ffff8808632c3d08> >> > CR2: ffff880870187ed8 >> > >> > The patch fixes the crash, but doesn't help with getting GPU in guest >> > working again. >> > >> > Any ideas? >> > >> > --- >> > drivers/gpu/vga/vgaarb.c | 6 ++++-- >> > 1 file changed, 4 insertions(+), 2 deletions(-) >> > >> > diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c >> > index 3166e4bc4eb6..9abcaa53bd25 100644 >> > --- a/drivers/gpu/vga/vgaarb.c >> > +++ b/drivers/gpu/vga/vgaarb.c >> > @@ -395,8 +395,10 @@ int vga_get(struct pci_dev *pdev, unsigned int rsrc, int interruptible) >> > set_current_state(interruptible ? >> > TASK_INTERRUPTIBLE : >> > TASK_UNINTERRUPTIBLE); >> > - if (signal_pending(current)) { >> > - rc = -EINTR; >> > + if (interruptible && signal_pending(current)) { >> > + __set_current_state(TASK_RUNNING); >> > + remove_wait_queue(&vga_wait_queue, &wait); >> > + rc = -ERESTARTSYS; >> > break; >> >> All 3 points are valid, and the patch looks good to me: >> >> Reviewed-by: David Herrmann <dh.herrmann@gmail.com> >> >> However, there seems to be a race between vga_lock and putting the >> thread asleep. > > I'm not sure I understand the race you're talking about. > Could you elaborate? Normal wake-up race. You have to check the condition you wait for *after* linking your wait-queue and setting your thread-state. In the current code, if the wake-up happens between spin_unlock_irqrestore() and add_wait_queue(), you will never get woken up. Thanks David
On Mon, Dec 14, 2015 at 11:20:00AM +0100, David Herrmann wrote: > Hi > > On Mon, Dec 14, 2015 at 9:19 AM, Kirill A. Shutemov > <kirill@shutemov.name> wrote: > > On Thu, Dec 10, 2015 at 11:28:58AM +0100, David Herrmann wrote: > >> Hi > >> > >> On Mon, Nov 30, 2015 at 3:17 AM, Kirill A. Shutemov > >> <kirill@shutemov.name> wrote: > >> > There are few defects in vga_get() related to signal hadning: > >> > > >> > - we shouldn't check for pending signals for TASK_UNINTERRUPTIBLE > >> > case; > >> > > >> > - if we found pending signal we must remove ourself from wait queue > >> > and change task state back to running; > >> > > >> > - -ERESTARTSYS is more appropriate, I guess. > >> > > >> > Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name> > >> > --- > >> > > >> > Alex, I try to get KVM with VGA passthrough working properly. I have i915 > >> > (HD 4600) on the host and GTX 580 for the guest. The guest GPU is not > >> > capabale of EFI, so I have to use x-vga=on. It's kinda work with your > >> > patch for i915.enable_hd_vgaarb=1. But guest refuse to initialize the GPU > >> > after KVM was not shut down correctly, resulting in host crash like this: > >> > > >> > BUG: unable to handle kernel paging request at ffff880870187ed8 > >> > IP: [<ffff880870187ed8>] 0xffff880870187ed8 > >> > PGD 2129067 PUD 80000008400001e3 > >> > Oops: 0011 [#1] PREEMPT SMP > >> > Modules linked in: iwlmvm iwlwifi > >> > CPU: 6 PID: 3983 Comm: qemu-system-x86 Not tainted 4.3.0-gentoo #6 > >> > Hardware name: Gigabyte Technology Co., Ltd. Z87X-UD7 TH/Z87X-UD7 TH-CF, BIOS F5a 06/12/2014 > >> > task: ffff88087a910000 ti: ffff8808632c0000 task.ti: ffff8808632c0000 > >> > RIP: 0010:[<ffff880870187ed8>] [<ffff880870187ed8>] 0xffff880870187ed8 > >> > RSP: 0018:ffff8808632c3d08 EFLAGS: 00010006 > >> > RAX: ffff880870187db0 RBX: 0000000070187f58 RCX: 0000000000000000 > >> > RDX: 0000000000000000 RSI: 0000000000000003 RDI: ffff880870187db0 > >> > RBP: ffff8808632c3d48 R08: 0000000000000000 R09: 0000000000000000 > >> > R10: 00000000000103c0 R11: 0000000000000293 R12: ffffffff81ea03c8 > >> > R13: ffffffff8104c7cb R14: 0000000000000000 R15: 0000000000000003 > >> > FS: 00007f984f9b2700(0000) GS:ffff88089f380000(0000) knlGS:0000000000000000 > >> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > >> > CR2: ffff880870187ed8 CR3: 00000008645f8000 CR4: 00000000001426e0 > >> > Stack: > >> > ffffffff810cc83d 00000000632c3d28 0000000000000000 ffffffff81ea03c0 > >> > 0000000000000046 0000000000000003 0000000000000000 0000000000000000 > >> > ffff8808632c3d80 ffffffff810cca44 ffff88087af63800 0000000000000286 > >> > Call Trace: > >> > [<ffffffff810cc83d>] ? __wake_up_common+0x4d/0x80 > >> > [<ffffffff810cca44>] __wake_up+0x34/0x50 > >> > [<ffffffff815d99e3>] __vga_put+0x73/0xd0 > >> > [<ffffffff815d9db4>] vga_put+0x54/0x80 > >> > [<ffffffff8169d042>] vfio_pci_vga_rw+0x1d2/0x220 > >> > [<ffffffff8169a7f3>] vfio_pci_rw+0x33/0x60 > >> > [<ffffffff8169abf7>] vfio_pci_write+0x17/0x20 > >> > [<ffffffff816966a6>] vfio_device_fops_write+0x26/0x30 > >> > [<ffffffff811a4b23>] __vfs_write+0x23/0xe0 > >> > [<ffffffff811a4a53>] ? __vfs_read+0x23/0xd0 > >> > [<ffffffff811b6e35>] ? do_vfs_ioctl+0x2b5/0x490 > >> > [<ffffffff811a5194>] vfs_write+0xa4/0x190 > >> > [<ffffffff811a5fa6>] SyS_pwrite64+0x66/0xa0 > >> > [<ffffffff819a17d7>] entry_SYSCALL_64_fastpath+0x12/0x6a > >> > Code: 88 ff ff e0 7e 18 70 08 88 ff ff 00 8c 57 76 08 88 ff ff 20 7f 18 70 08 88 ff ff 08 7f 18 70 08 88 ff ff 94 51 1a 81 ff ff ff ff <09> 00 00 00 00 00 00 00 01 8c 57 76 08 88 ff ff 00 8c 57 76 08 > >> > RIP [<ffff880870187ed8>] 0xffff880870187ed8 > >> > RSP <ffff8808632c3d08> > >> > CR2: ffff880870187ed8 > >> > > >> > The patch fixes the crash, but doesn't help with getting GPU in guest > >> > working again. > >> > > >> > Any ideas? > >> > > >> > --- > >> > drivers/gpu/vga/vgaarb.c | 6 ++++-- > >> > 1 file changed, 4 insertions(+), 2 deletions(-) > >> > > >> > diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c > >> > index 3166e4bc4eb6..9abcaa53bd25 100644 > >> > --- a/drivers/gpu/vga/vgaarb.c > >> > +++ b/drivers/gpu/vga/vgaarb.c > >> > @@ -395,8 +395,10 @@ int vga_get(struct pci_dev *pdev, unsigned int rsrc, int interruptible) > >> > set_current_state(interruptible ? > >> > TASK_INTERRUPTIBLE : > >> > TASK_UNINTERRUPTIBLE); > >> > - if (signal_pending(current)) { > >> > - rc = -EINTR; > >> > + if (interruptible && signal_pending(current)) { > >> > + __set_current_state(TASK_RUNNING); > >> > + remove_wait_queue(&vga_wait_queue, &wait); > >> > + rc = -ERESTARTSYS; > >> > break; > >> > >> All 3 points are valid, and the patch looks good to me: > >> > >> Reviewed-by: David Herrmann <dh.herrmann@gmail.com> > >> > >> However, there seems to be a race between vga_lock and putting the > >> thread asleep. > > > > I'm not sure I understand the race you're talking about. > > Could you elaborate? > > Normal wake-up race. You have to check the condition you wait for > *after* linking your wait-queue and setting your thread-state. In the > current code, if the wake-up happens between spin_unlock_irqrestore() > and add_wait_queue(), you will never get woken up. Ah, I see. Your patch looks good to me to fix the issue.
diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c index a0b4334..82cf1e3 100644 --- a/drivers/gpu/vga/vgaarb.c +++ b/drivers/gpu/vga/vgaarb.c @@ -359,8 +359,8 @@ static void __vga_put int vga_get(struct pci_dev *pdev, unsigned int rsrc, int interruptible) { struct vga_device *vgadev, *conflict; + DECLARE_WAITQUEUE(wait, current); unsigned long flags; - wait_queue_t wait; int rc = 0; vga_check_first_use(); @@ -371,6 +371,11 @@ int vga_get return 0; for (;;) { + add_wait_queue(&vga_wait_queue, &wait); + set_current_state(interruptible ? + TASK_INTERRUPTIBLE : + TASK_UNINTERRUPTIBLE); + spin_lock_irqsave(&vga_lock, flags); vgadev = vgadev_find(pdev); if (vgadev == NULL) { @@ -383,25 +388,22 @@ int vga_get(struct pci_dev *pdev, unsigned int rsrc, int interruptible) if (conflict == NULL) break; - /* We have a conflict, we wait until somebody kicks the * work queue. Currently we have one work queue that we * kick each time some resources are released, but it would * be fairly easy to have a per device one so that we only * need to attach to the conflicting device */ - init_waitqueue_entry(&wait, current); - add_wait_queue(&vga_wait_queue, &wait); - set_current_state(interruptible ? - TASK_INTERRUPTIBLE : - TASK_UNINTERRUPTIBLE); - if (signal_pending(current)) { - rc = -EINTR; + if (interruptible && signal_pending(current)) { + rc = -ERESTARTSYS; break; } schedule(); remove_wait_queue(&vga_wait_queue, &wait); } + + __set_current_state(TASK_RUNNING); + remove_wait_queue(&vga_wait_queue, &wait); return rc; }