2022-10-21 06:34:13

by Huang, Shaoqin

Subject: [PATCH 0/2] virtio: use helper function is_power_of_2()

From: Shaoqin Huang <[email protected]>

Use helper function is_power_of_2() to check if num is power of two.
Minor readability improvement.

Shaoqin Huang (2):
virtio_pci: use helper function is_power_of_2()
virtio_ring: use helper function is_power_of_2()

drivers/virtio/virtio_pci_modern.c | 2 +-
drivers/virtio/virtio_ring.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

--
2.34.1

2022-10-21 06:34:29

by Huang, Shaoqin

Subject: [PATCH 1/2] virtio_pci: use helper function is_power_of_2()

From: Shaoqin Huang <[email protected]>

Use helper function is_power_of_2() to check if num is power of two.
Minor readability improvement.

Signed-off-by: Shaoqin Huang <[email protected]>
---
drivers/virtio/virtio_pci_modern.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
index c3b9f2761849..207294bd7b9d 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c
@@ -310,7 +310,7 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
if (!num || vp_modern_get_queue_enable(mdev, index))
return ERR_PTR(-ENOENT);

- if (num & (num - 1)) {
+ if (!is_power_of_2(num)) {
dev_warn(&vp_dev->pci_dev->dev, "bad queue size %u", num);
return ERR_PTR(-EINVAL);
}
--
2.34.1

2022-10-21 06:35:00

by Huang, Shaoqin

Subject: [PATCH 2/2] virtio_ring: use helper function is_power_of_2()

From: Shaoqin Huang <[email protected]>

Use helper function is_power_of_2() to check if num is power of two.
Minor readability improvement.

Signed-off-by: Shaoqin Huang <[email protected]>
---
drivers/virtio/virtio_ring.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 2e7689bb933b..723c4e29e1d3 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1052,7 +1052,7 @@ static int vring_alloc_queue_split(struct vring_virtqueue_split *vring_split,
dma_addr_t dma_addr;

/* We assume num is a power of 2. */
- if (num & (num - 1)) {
+ if (!is_power_of_2(num)) {
dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
return -EINVAL;
}
--
2.34.1

2022-10-21 09:02:48

by Philippe Mathieu-Daudé

Subject: Re: [PATCH 1/2] virtio_pci: use helper function is_power_of_2()

On 21/10/22 08:27, [email protected] wrote:
> From: Shaoqin Huang <[email protected]>
>
> Use helper function is_power_of_2() to check if num is power of two.
> Minor readability improvement.
>
> Signed-off-by: Shaoqin Huang <[email protected]>
> ---
> drivers/virtio/virtio_pci_modern.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Philippe Mathieu-Daudé <[email protected]>

2022-10-21 09:09:40

by Philippe Mathieu-Daudé

Subject: Re: [PATCH 2/2] virtio_ring: use helper function is_power_of_2()

On 21/10/22 08:27, [email protected] wrote:
> From: Shaoqin Huang <[email protected]>
>
> Use helper function is_power_of_2() to check if num is power of two.
> Minor readability improvement.
>
> Signed-off-by: Shaoqin Huang <[email protected]>
> ---
> drivers/virtio/virtio_ring.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 2e7689bb933b..723c4e29e1d3 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -1052,7 +1052,7 @@ static int vring_alloc_queue_split(struct vring_virtqueue_split *vring_split,
> dma_addr_t dma_addr;
>
> /* We assume num is a power of 2. */
> - if (num & (num - 1)) {
> + if (!is_power_of_2(num)) {
> dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
> return -EINVAL;
> }

This makes the following code unreachable:

if (!num)
return -ENOMEM;

Do we want to move it earlier or remove it?

Regards,

Phil.

2022-10-22 12:53:14

by Huang, Shaoqin

Subject: Re: [PATCH 2/2] virtio_ring: use helper function is_power_of_2()

On 10/21/2022 4:53 PM, Philippe Mathieu-Daudé wrote:
> On 21/10/22 08:27, [email protected] wrote:
>> From: Shaoqin Huang <[email protected]>
>>
>> Use helper function is_power_of_2() to check if num is power of two.
>> Minor readability improvement.
>>
>> Signed-off-by: Shaoqin Huang <[email protected]>
>> ---
>>   drivers/virtio/virtio_ring.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
>> index 2e7689bb933b..723c4e29e1d3 100644
>> --- a/drivers/virtio/virtio_ring.c
>> +++ b/drivers/virtio/virtio_ring.c
>> @@ -1052,7 +1052,7 @@ static int vring_alloc_queue_split(struct
>> vring_virtqueue_split *vring_split,
>>       dma_addr_t dma_addr;
>>       /* We assume num is a power of 2. */
>> -    if (num & (num - 1)) {
>> +    if (!is_power_of_2(num)) {
>>           dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
>>           return -EINVAL;
>>       }
>
> This makes the following code unreachable:
>
>     if (!num)
>         return -ENOMEM;
>
> Do we want to move it earlier or remove it?
>

I think the following code can still be executed if num > 0, and if
there if no enough memory, the allocation of the vring will failed and
will decrease the num by divide 2, this will makes num equal to 0. And
then trigger the check and return -ENOMEM.

> Regards,
>
> Phil.

2022-10-24 12:36:24

by Xuan Zhuo

Subject: Re: [PATCH 1/2] virtio_pci: use helper function is_power_of_2()

On Thu, 20 Oct 2022 23:27:33 -0700, [email protected] wrote:
> From: Shaoqin Huang <[email protected]>
>
> Use helper function is_power_of_2() to check if num is power of two.
> Minor readability improvement.
>
> Signed-off-by: Shaoqin Huang <[email protected]>

Reviewed-by: Xuan Zhuo <[email protected]>

> ---
> drivers/virtio/virtio_pci_modern.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> index c3b9f2761849..207294bd7b9d 100644
> --- a/drivers/virtio/virtio_pci_modern.c
> +++ b/drivers/virtio/virtio_pci_modern.c
> @@ -310,7 +310,7 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
> if (!num || vp_modern_get_queue_enable(mdev, index))
> return ERR_PTR(-ENOENT);
>
> - if (num & (num - 1)) {
> + if (!is_power_of_2(num)) {
> dev_warn(&vp_dev->pci_dev->dev, "bad queue size %u", num);
> return ERR_PTR(-EINVAL);
> }
> --
> 2.34.1
>
> _______________________________________________
> Virtualization mailing list
> [email protected]
> https://lists.linuxfoundation.org/mailman/listinfo/virtualization

2022-10-24 12:41:03

by Xuan Zhuo

Subject: Re: [PATCH 2/2] virtio_ring: use helper function is_power_of_2()

On Thu, 20 Oct 2022 23:27:34 -0700, [email protected] wrote:
> From: Shaoqin Huang <[email protected]>
>
> Use helper function is_power_of_2() to check if num is power of two.
> Minor readability improvement.
>
> Signed-off-by: Shaoqin Huang <[email protected]>
Reviewed-by: Xuan Zhuo <[email protected]>
> ---
> drivers/virtio/virtio_ring.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 2e7689bb933b..723c4e29e1d3 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -1052,7 +1052,7 @@ static int vring_alloc_queue_split(struct vring_virtqueue_split *vring_split,
> dma_addr_t dma_addr;
>
> /* We assume num is a power of 2. */
> - if (num & (num - 1)) {
> + if (!is_power_of_2(num)) {
> dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
> return -EINVAL;
> }
> --
> 2.34.1
>
> _______________________________________________
> Virtualization mailing list
> [email protected]
> https://lists.linuxfoundation.org/mailman/listinfo/virtualization