* [PATCH 4/4] kvm tools: Fix virtio console hangs by removing IRQ injection for tx path
@ 2011-05-08 2:38 Asias He
2011-05-08 6:22 ` Ingo Molnar
0 siblings, 1 reply; 3+ messages in thread
From: Asias He @ 2011-05-08 2:38 UTC (permalink / raw)
To: Pekka Enberg, Cyrill Gorcunov, Ingo Molnar, Sasha Levin,
Prasad Joshi
Cc: kvm, Asias He
As virtio spec says:
"""
Because this is high importance and low bandwidth, the current Linux
implementation polls for the buffer to be used, rather than waiting
for an interrupt, simplifying the implementation signicantly.
"""
drivers/char/virtio_console.c
send_buf() {
...
/* Tell Host to go! */
virtqueue_kick(out_vq);
...
while (!virtqueue_get_buf(out_vq, &len))
cpu_relax();
...
}
The console hangs can simply be reproduced by yes command which
gives tremendous console IOs and IRQs.
[ 16.786440] irq 4: nobody cared (try booting with the "irqpoll" option)
[ 16.786440] Pid: 1437, comm: yes Tainted: G W 2.6.39-rc6+ #56
[ 16.786440] Call Trace:
[ 16.786440] [<c16578eb>] __report_bad_irq+0x30/0x89
[ 16.786440] [<c10980e6>] note_interrupt+0x118/0x17a
[ 16.786440] [<c1096e7d>] handle_irq_event_percpu+0x168/0x179
[ 16.786440] [<c1096eba>] handle_irq_event+0x2c/0x46
[ 16.786440] [<c1098516>] ? unmask_irq+0x1e/0x1e
[ 16.786440] [<c1098566>] handle_level_irq+0x50/0x6e
[ 16.786440] <IRQ> [<c102fa69>] ? do_IRQ+0x35/0x7f
[ 16.786440] [<c1665ea9>] ? common_interrupt+0x29/0x30
[ 16.786440] [<c16610d6>] ? _raw_spin_unlock_irqrestore+0x7/0x28
[ 16.786440] [<c1364f65>] ? hvc_write+0x88/0x9e
[ 16.786440] [<c1355500>] ? do_output_char+0x88/0x18a
[ 16.786440] [<c1355631>] ? process_output+0x2f/0x42
[ 16.786440] [<c1355af6>] ? n_tty_write+0x211/0x2dc
[ 16.786440] [<c1059d77>] ? try_to_wake_up+0x226/0x226
[ 16.786440] [<c13534a4>] ? tty_write+0x15e/0x1d1
[ 16.786440] [<c12c1644>] ? security_file_permission+0x22/0x26
[ 16.786440] [<c13558e5>] ? process_echoes+0x241/0x241
[ 16.786440] [<c10dd9d2>] ? vfs_write+0x84/0xd7
[ 16.786440] [<c1353346>] ? tty_write_lock+0x3d/0x3d
[ 16.786440] [<c10ddb92>] ? sys_write+0x3b/0x5d
[ 16.786440] [<c166594c>] ? sysenter_do_call+0x12/0x22
[ 16.786440] handlers:
[ 16.786440] [<c1351397>] (vp_interrupt+0x0/0x3a)
[ 16.786440] Disabling IRQ #4
Signed-off-by: Asias He <asias.hejun@gmail.com>
---
tools/kvm/virtio/console.c | 2 --
1 files changed, 0 insertions(+), 2 deletions(-)
diff --git a/tools/kvm/virtio/console.c b/tools/kvm/virtio/console.c
index f5449ba..1fecf37 100644
--- a/tools/kvm/virtio/console.c
+++ b/tools/kvm/virtio/console.c
@@ -171,8 +171,6 @@ static void virtio_console_handle_callback(struct kvm *self, void *param)
len = term_putc_iov(CONSOLE_VIRTIO, iov, out);
virt_queue__set_used_elem(vq, head, len);
}
-
- virt_queue__trigger_irq(vq, virtio_console_pci_device.irq_line, &cdev.isr, self);
}
static bool virtio_console_pci_io_out(struct kvm *self, u16 port, void *data, int size, u32 count)
--
1.7.5.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH 4/4] kvm tools: Fix virtio console hangs by removing IRQ injection for tx path
2011-05-08 2:38 [PATCH 4/4] kvm tools: Fix virtio console hangs by removing IRQ injection for tx path Asias He
@ 2011-05-08 6:22 ` Ingo Molnar
2011-05-08 12:59 ` Asias He
0 siblings, 1 reply; 3+ messages in thread
From: Ingo Molnar @ 2011-05-08 6:22 UTC (permalink / raw)
To: Asias He; +Cc: Pekka Enberg, Cyrill Gorcunov, Sasha Levin, Prasad Joshi, kvm
* Asias He <asias.hejun@gmail.com> wrote:
> As virtio spec says:
>
> """
> Because this is high importance and low bandwidth, the current Linux
> implementation polls for the buffer to be used, rather than waiting
> for an interrupt, simplifying the implementation signicantly.
> """
>
> drivers/char/virtio_console.c
> send_buf() {
> ...
> /* Tell Host to go! */
> virtqueue_kick(out_vq);
> ...
> while (!virtqueue_get_buf(out_vq, &len))
> cpu_relax();
> ...
> }
>
> The console hangs can simply be reproduced by yes command which
> gives tremendous console IOs and IRQs.
>
> [ 16.786440] irq 4: nobody cared (try booting with the "irqpoll" option)
> [ 16.786440] Pid: 1437, comm: yes Tainted: G W 2.6.39-rc6+ #56
> [ 16.786440] Call Trace:
> [ 16.786440] [<c16578eb>] __report_bad_irq+0x30/0x89
> [ 16.786440] [<c10980e6>] note_interrupt+0x118/0x17a
> [ 16.786440] [<c1096e7d>] handle_irq_event_percpu+0x168/0x179
> [ 16.786440] [<c1096eba>] handle_irq_event+0x2c/0x46
> [ 16.786440] [<c1098516>] ? unmask_irq+0x1e/0x1e
> [ 16.786440] [<c1098566>] handle_level_irq+0x50/0x6e
> [ 16.786440] <IRQ> [<c102fa69>] ? do_IRQ+0x35/0x7f
> [ 16.786440] [<c1665ea9>] ? common_interrupt+0x29/0x30
> [ 16.786440] [<c16610d6>] ? _raw_spin_unlock_irqrestore+0x7/0x28
> [ 16.786440] [<c1364f65>] ? hvc_write+0x88/0x9e
> [ 16.786440] [<c1355500>] ? do_output_char+0x88/0x18a
> [ 16.786440] [<c1355631>] ? process_output+0x2f/0x42
> [ 16.786440] [<c1355af6>] ? n_tty_write+0x211/0x2dc
> [ 16.786440] [<c1059d77>] ? try_to_wake_up+0x226/0x226
> [ 16.786440] [<c13534a4>] ? tty_write+0x15e/0x1d1
> [ 16.786440] [<c12c1644>] ? security_file_permission+0x22/0x26
> [ 16.786440] [<c13558e5>] ? process_echoes+0x241/0x241
> [ 16.786440] [<c10dd9d2>] ? vfs_write+0x84/0xd7
> [ 16.786440] [<c1353346>] ? tty_write_lock+0x3d/0x3d
> [ 16.786440] [<c10ddb92>] ? sys_write+0x3b/0x5d
> [ 16.786440] [<c166594c>] ? sysenter_do_call+0x12/0x22
> [ 16.786440] handlers:
> [ 16.786440] [<c1351397>] (vp_interrupt+0x0/0x3a)
> [ 16.786440] Disabling IRQ #4
Hm, why is irq #4 active if the guest-side virtio console driver does not
handle it?
> Signed-off-by: Asias He <asias.hejun@gmail.com>
> ---
> tools/kvm/virtio/console.c | 2 --
> 1 files changed, 0 insertions(+), 2 deletions(-)
>
> diff --git a/tools/kvm/virtio/console.c b/tools/kvm/virtio/console.c
> index f5449ba..1fecf37 100644
> --- a/tools/kvm/virtio/console.c
> +++ b/tools/kvm/virtio/console.c
> @@ -171,8 +171,6 @@ static void virtio_console_handle_callback(struct kvm *self, void *param)
> len = term_putc_iov(CONSOLE_VIRTIO, iov, out);
> virt_queue__set_used_elem(vq, head, len);
> }
> -
> - virt_queue__trigger_irq(vq, virtio_console_pci_device.irq_line, &cdev.isr, self);
> }
I think this at least requires a comment at that place, that we intentionally
skip notifying the guest, because Linux guests do not use the console IRQ.
Does the guest-side virtio driver *ever* use the irq?
Thanks,
Ingo
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH 4/4] kvm tools: Fix virtio console hangs by removing IRQ injection for tx path
2011-05-08 6:22 ` Ingo Molnar
@ 2011-05-08 12:59 ` Asias He
0 siblings, 0 replies; 3+ messages in thread
From: Asias He @ 2011-05-08 12:59 UTC (permalink / raw)
To: Ingo Molnar; +Cc: Pekka Enberg, Cyrill Gorcunov, Sasha Levin, Prasad Joshi, kvm
On 05/08/2011 02:22 PM, Ingo Molnar wrote:
>
> * Asias He <asias.hejun@gmail.com> wrote:
>
>> As virtio spec says:
>>
>> """
>> Because this is high importance and low bandwidth, the current Linux
>> implementation polls for the buffer to be used, rather than waiting
>> for an interrupt, simplifying the implementation signicantly.
>> """
>>
>> drivers/char/virtio_console.c
>> send_buf() {
>> ...
>> /* Tell Host to go! */
>> virtqueue_kick(out_vq);
>> ...
>> while (!virtqueue_get_buf(out_vq, &len))
>> cpu_relax();
>> ...
>> }
>>
>> The console hangs can simply be reproduced by yes command which
>> gives tremendous console IOs and IRQs.
>>
>> [ 16.786440] irq 4: nobody cared (try booting with the "irqpoll" option)
>> [ 16.786440] Pid: 1437, comm: yes Tainted: G W 2.6.39-rc6+ #56
>> [ 16.786440] Call Trace:
>> [ 16.786440] [<c16578eb>] __report_bad_irq+0x30/0x89
>> [ 16.786440] [<c10980e6>] note_interrupt+0x118/0x17a
>> [ 16.786440] [<c1096e7d>] handle_irq_event_percpu+0x168/0x179
>> [ 16.786440] [<c1096eba>] handle_irq_event+0x2c/0x46
>> [ 16.786440] [<c1098516>] ? unmask_irq+0x1e/0x1e
>> [ 16.786440] [<c1098566>] handle_level_irq+0x50/0x6e
>> [ 16.786440] <IRQ> [<c102fa69>] ? do_IRQ+0x35/0x7f
>> [ 16.786440] [<c1665ea9>] ? common_interrupt+0x29/0x30
>> [ 16.786440] [<c16610d6>] ? _raw_spin_unlock_irqrestore+0x7/0x28
>> [ 16.786440] [<c1364f65>] ? hvc_write+0x88/0x9e
>> [ 16.786440] [<c1355500>] ? do_output_char+0x88/0x18a
>> [ 16.786440] [<c1355631>] ? process_output+0x2f/0x42
>> [ 16.786440] [<c1355af6>] ? n_tty_write+0x211/0x2dc
>> [ 16.786440] [<c1059d77>] ? try_to_wake_up+0x226/0x226
>> [ 16.786440] [<c13534a4>] ? tty_write+0x15e/0x1d1
>> [ 16.786440] [<c12c1644>] ? security_file_permission+0x22/0x26
>> [ 16.786440] [<c13558e5>] ? process_echoes+0x241/0x241
>> [ 16.786440] [<c10dd9d2>] ? vfs_write+0x84/0xd7
>> [ 16.786440] [<c1353346>] ? tty_write_lock+0x3d/0x3d
>> [ 16.786440] [<c10ddb92>] ? sys_write+0x3b/0x5d
>> [ 16.786440] [<c166594c>] ? sysenter_do_call+0x12/0x22
>> [ 16.786440] handlers:
>> [ 16.786440] [<c1351397>] (vp_interrupt+0x0/0x3a)
>> [ 16.786440] Disabling IRQ #4
>
> Hm, why is irq #4 active if the guest-side virtio console driver does not
> handle it?
>
>> Signed-off-by: Asias He <asias.hejun@gmail.com>
>> ---
>> tools/kvm/virtio/console.c | 2 --
>> 1 files changed, 0 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/kvm/virtio/console.c b/tools/kvm/virtio/console.c
>> index f5449ba..1fecf37 100644
>> --- a/tools/kvm/virtio/console.c
>> +++ b/tools/kvm/virtio/console.c
>> @@ -171,8 +171,6 @@ static void virtio_console_handle_callback(struct kvm *self, void *param)
>> len = term_putc_iov(CONSOLE_VIRTIO, iov, out);
>> virt_queue__set_used_elem(vq, head, len);
>> }
>> -
>> - virt_queue__trigger_irq(vq, virtio_console_pci_device.irq_line, &cdev.isr, self);
>> }
>
> I think this at least requires a comment at that place, that we intentionally
> skip notifying the guest, because Linux guests do not use the console IRQ.
Will do.
> Does the guest-side virtio driver *ever* use the irq?
Yes. They use IRQ at least for the RX path.
> Thanks,
>
> Ingo
>
--
Best Regards,
Asias He
^ permalink raw reply [flat|nested] 3+ messages in thread
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2011-05-08 2:38 [PATCH 4/4] kvm tools: Fix virtio console hangs by removing IRQ injection for tx path Asias He
2011-05-08 6:22 ` Ingo Molnar
2011-05-08 12:59 ` Asias He
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