thr3ads.net - Linux Virtualization - [PATCH v2 2/2] virtio-pci: check name when counting MSI-X vectors [Jan 2020]

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Daniel Verkamp

2020-Jan-03 18:40 UTC

[PATCH v2 1/2] virtio-balloon: initialize all vq callbacks

Ensure that elements of the callbacks array that correspond to
unavailable features are set to NULL; previously, they would be left
uninitialized.

Since the corresponding names array elements were explicitly set to
NULL, the uninitialized callback pointers would not actually be
dereferenced; however, the uninitialized callbacks elements would still
be read in vp_find_vqs_msix() and used to calculate the number of MSI-X
vectors required.

Cc: stable at vger.kernel.org
Fixes: 86a559787e6f ("virtio-balloon:
VIRTIO_BALLOON_F_FREE_PAGE_HINT")
Reviewed-by: Cornelia Huck <cohuck at redhat.com>
Signed-off-by: Daniel Verkamp <dverkamp at chromium.org>
---

v1:
https://lists.linuxfoundation.org/pipermail/virtualization/2019-December/044829.html

Changes from v1:
- Clarified "array" in commit message to "callbacks array"

 drivers/virtio/virtio_balloon.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 93f995f6cf36..8e400ece9273 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -475,7 +475,9 @@ static int init_vqs(struct virtio_balloon *vb)
 	names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
 	callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
 	names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
+	callbacks[VIRTIO_BALLOON_VQ_STATS] = NULL;
 	names[VIRTIO_BALLOON_VQ_STATS] = NULL;
+	callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
 	names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
 
 	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
-- 
2.24.1.735.g03f4e72817-goog

Daniel Verkamp

2020-Jan-03 18:40 UTC

head link

[PATCH v2 2/2] virtio-pci: check name when counting MSI-X vectors

VQs without a name specified are not valid; they are skipped in the
later loop that assigns MSI-X vectors to queues, but the per_vq_vectors
loop above that counts the required number of vectors previously still
counted any queue with a non-NULL callback as needing a vector.

Add a check to the per_vq_vectors loop so that vectors with no name are
not counted to make the two loops consistent.  This prevents
over-counting unnecessary vectors (e.g. for features which were not
negotiated with the device).

Cc: stable at vger.kernel.org
Fixes: 86a559787e6f ("virtio-balloon:
VIRTIO_BALLOON_F_FREE_PAGE_HINT")
Reviewed-by: Cornelia Huck <cohuck at redhat.com>
Signed-off-by: Daniel Verkamp <dverkamp at chromium.org>
---

v1:
https://lists.linuxfoundation.org/pipermail/virtualization/2019-December/044828.html

 drivers/virtio/virtio_pci_common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_pci_common.c
b/drivers/virtio/virtio_pci_common.c
index f2862f66c2ac..222d630c41fc 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -294,7 +294,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev,
unsigned nvqs,
 		/* Best option: one for change interrupt, one per vq. */
 		nvectors = 1;
 		for (i = 0; i < nvqs; ++i)
-			if (callbacks[i])
+			if (names[i] && callbacks[i])
 				++nvectors;
 	} else {
 		/* Second best: one for change, shared for all vqs. */
-- 
2.24.1.735.g03f4e72817-goog

Wang, Wei W

2020-Jan-05 12:24 UTC

head link

[PATCH v2 1/2] virtio-balloon: initialize all vq callbacks

On Saturday, January 4, 2020 2:41 AM, Daniel Verkamp
wrote:> Subject: [PATCH v2 1/2] virtio-balloon: initialize all vq callbacks
> 
> Ensure that elements of the callbacks array that correspond to unavailable
> features are set to NULL; previously, they would be left uninitialized.
> 
> Since the corresponding names array elements were explicitly set to NULL,
> the uninitialized callback pointers would not actually be dereferenced;
> however, the uninitialized callbacks elements would still be read in 
> vp_find_vqs_msix() and used to calculate the number of MSI-X vectors
> required.
The above description doesn't seem true after your second patch gets
applied.
 > Cc: stable at vger.kernel.org
> Fixes: 86a559787e6f ("virtio-balloon:
> VIRTIO_BALLOON_F_FREE_PAGE_HINT")
> Reviewed-by: Cornelia Huck <cohuck at redhat.com>
> Signed-off-by: Daniel Verkamp <dverkamp at chromium.org>
> ---
> 
> v1:
> https://lists.linuxfoundation.org/pipermail/virtualization/2019-December/04
> 4829.html
> 
> Changes from v1:
> - Clarified "array" in commit message to "callbacks
array"
> 
>  drivers/virtio/virtio_balloon.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/virtio/virtio_balloon.c
b/drivers/virtio/virtio_balloon.c
> index 93f995f6cf36..8e400ece9273 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -475,7 +475,9 @@ static int init_vqs(struct virtio_balloon *vb)
>  	names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
>  	callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
>  	names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
> +	callbacks[VIRTIO_BALLOON_VQ_STATS] = NULL;
>  	names[VIRTIO_BALLOON_VQ_STATS] = NULL;
> +	callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
Could you remove other redundant NULL initialization well?
https://lists.linuxfoundation.org/pipermail/virtualization/2019-December/044837.html

Best,
Wei

Wang, Wei W

2020-Jan-05 12:27 UTC

head link

[PATCH v2 2/2] virtio-pci: check name when counting MSI-X vectors

On Saturday, January 4, 2020 2:41 AM, Daniel Verkamp
wrote:> Subject: [PATCH v2 2/2] virtio-pci: check name when counting MSI-X vectors
> 
> VQs without a name specified are not valid; they are skipped in the later
loop
> that assigns MSI-X vectors to queues, but the per_vq_vectors loop above
that
> counts the required number of vectors previously still counted any queue
with a
> non-NULL callback as needing a vector.
> 
> Add a check to the per_vq_vectors loop so that vectors with no name are not
> counted to make the two loops consistent.  This prevents over-counting
> unnecessary vectors (e.g. for features which were not negotiated with the
> device).
> 
> Cc: stable at vger.kernel.org
> Fixes: 86a559787e6f ("virtio-balloon:
VIRTIO_BALLOON_F_FREE_PAGE_HINT")
> Reviewed-by: Cornelia Huck <cohuck at redhat.com>
> Signed-off-by: Daniel Verkamp <dverkamp at chromium.org>
> ---
> 
> v1:
>
https://lists.linuxfoundation.org/pipermail/virtualization/2019-December/0448
> 28.html
> 
>  drivers/virtio/virtio_pci_common.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/virtio/virtio_pci_common.c
> b/drivers/virtio/virtio_pci_common.c
> index f2862f66c2ac..222d630c41fc 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -294,7 +294,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev,
> unsigned nvqs,
>  		/* Best option: one for change interrupt, one per vq. */
>  		nvectors = 1;
>  		for (i = 0; i < nvqs; ++i)
> -			if (callbacks[i])
> +			if (names[i] && callbacks[i])
>  				++nvectors;
>  	} else {
>  		/* Second best: one for change, shared for all vqs. */
> --
> 2.24.1.735.g03f4e72817-goog
Reviewed-by: Wang, Wei W <wei.w.wang at intel.com>

Best,
Wei

Michael S. Tsirkin

2020-Jan-05 13:25 UTC

head link

[PATCH v2 1/2] virtio-balloon: initialize all vq callbacks

On Sun, Jan 05, 2020 at 12:24:11PM +0000, Wang, Wei W
wrote:> On Saturday, January 4, 2020 2:41 AM, Daniel Verkamp wrote:
> > Subject: [PATCH v2 1/2] virtio-balloon: initialize all vq callbacks
> > 
> > Ensure that elements of the callbacks array that correspond to
unavailable
> > features are set to NULL; previously, they would be left
uninitialized.
> > 
> > Since the corresponding names array elements were explicitly set to
NULL,
> > the uninitialized callback pointers would not actually be
dereferenced;
> > however, the uninitialized callbacks elements would still be read in 
> > vp_find_vqs_msix() and used to calculate the number of MSI-X vectors
> > required.
> 
> The above description doesn't seem true after your second patch gets
applied.
>  
> > Cc: stable at vger.kernel.org
> > Fixes: 86a559787e6f ("virtio-balloon:
> > VIRTIO_BALLOON_F_FREE_PAGE_HINT")
> > Reviewed-by: Cornelia Huck <cohuck at redhat.com>
> > Signed-off-by: Daniel Verkamp <dverkamp at chromium.org>
> > ---
> > 
> > v1:
> >
https://lists.linuxfoundation.org/pipermail/virtualization/2019-December/04
> > 4829.html
> > 
> > Changes from v1:
> > - Clarified "array" in commit message to "callbacks
array"
> > 
> >  drivers/virtio/virtio_balloon.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/virtio/virtio_balloon.c
b/drivers/virtio/virtio_balloon.c
> > index 93f995f6cf36..8e400ece9273 100644
> > --- a/drivers/virtio/virtio_balloon.c
> > +++ b/drivers/virtio/virtio_balloon.c
> > @@ -475,7 +475,9 @@ static int init_vqs(struct virtio_balloon *vb)
> >  	names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
> >  	callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
> >  	names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
> > +	callbacks[VIRTIO_BALLOON_VQ_STATS] = NULL;
> >  	names[VIRTIO_BALLOON_VQ_STATS] = NULL;
> > +	callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
> 
> Could you remove other redundant NULL initialization well?
>
https://lists.linuxfoundation.org/pipermail/virtualization/2019-December/044837.html
> 
> Best,
> Wei
I queued as is, can be tweaked by a patch on top.

-- 
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