nvme: Fix spurious interrupts

[Qemu-devel] [PATCH] nvme: Fix spurious interrupts

Posted by Keith Busch 6 years, 11 months ago

The code had asserted an interrupt every time it was requested to check
for new completion queue entries.This can result in spurious interrupts
seen by the guest OS.

Fix this by asserting an interrupt only if there are un-acknowledged
completion queue entries available.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Keith Busch <keith.busch@intel.com>
---
 hw/block/nvme.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/hw/block/nvme.c b/hw/block/nvme.c
index 9fbe5673cb..7c8c63e8f5 100644
--- a/hw/block/nvme.c
+++ b/hw/block/nvme.c
@@ -272,7 +272,9 @@ static void nvme_post_cqes(void *opaque)
             sizeof(req->cqe));
         QTAILQ_INSERT_TAIL(&sq->req_list, req, entry);
     }
-    nvme_irq_assert(n, cq);
+    if (cq->tail != cq->head) {
+        nvme_irq_assert(n, cq);
+    }
 }
 
 static void nvme_enqueue_req_completion(NvmeCQueue *cq, NvmeRequest *req)
-- 
2.14.4

Re: [Qemu-devel] [PATCH] nvme: Fix spurious interrupts

Posted by Guenter Roeck 6 years, 11 months ago

On Mon, Nov 26, 2018 at 10:17:45AM -0700, Keith Busch wrote:
> The code had asserted an interrupt every time it was requested to check
> for new completion queue entries.This can result in spurious interrupts
> seen by the guest OS.
> 
> Fix this by asserting an interrupt only if there are un-acknowledged
> completion queue entries available.
> 
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Signed-off-by: Keith Busch <keith.busch@intel.com>

Tested-by: Guenter Roeck <linux@roeck-us.net>

> ---
>  hw/block/nvme.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/block/nvme.c b/hw/block/nvme.c
> index 9fbe5673cb..7c8c63e8f5 100644
> --- a/hw/block/nvme.c
> +++ b/hw/block/nvme.c
> @@ -272,7 +272,9 @@ static void nvme_post_cqes(void *opaque)
>              sizeof(req->cqe));
>          QTAILQ_INSERT_TAIL(&sq->req_list, req, entry);
>      }
> -    nvme_irq_assert(n, cq);
> +    if (cq->tail != cq->head) {
> +        nvme_irq_assert(n, cq);
> +    }
>  }
>  
>  static void nvme_enqueue_req_completion(NvmeCQueue *cq, NvmeRequest *req)
> -- 
> 2.14.4
>

Re: [Qemu-devel] [PATCH] nvme: Fix spurious interrupts

Posted by Kevin Wolf 6 years, 11 months ago

Am 26.11.2018 um 18:17 hat Keith Busch geschrieben:
> The code had asserted an interrupt every time it was requested to check
> for new completion queue entries.This can result in spurious interrupts
> seen by the guest OS.
> 
> Fix this by asserting an interrupt only if there are un-acknowledged
> completion queue entries available.
> 
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Signed-off-by: Keith Busch <keith.busch@intel.com>

Thanks, applied to the block branch.

Kevin