Re: [PATCH 4/4] kvm tools: Fix virtio console hangs by removing IRQ injection for tx path
* Asias He asias.he...@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: GW 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.he...@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
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Re: [PATCH 4/4] kvm tools: Fix virtio console hangs by removing IRQ injection for tx path
On 05/08/2011 02:22 PM, Ingo Molnar wrote:
* Asias He asias.he...@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: GW 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.he...@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
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[PATCH 4/4] kvm tools: Fix virtio console hangs by removing IRQ injection for tx path
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: GW 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.he...@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
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