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SubjectRe: [RFC PATCH 10/10] vhost/vdpa: return configuration bytes read and written to user space
On Tue, Mar 02, 2021 at 12:05:35PM +0800, Jason Wang wrote:
>
>On 2021/2/16 5:44 下午, Stefano Garzarella wrote:
>>vdpa_get_config() and vdpa_set_config() now return the amount
>>of bytes read and written, so let's return them to the user space.
>>
>>We also modify vhost_vdpa_config_validate() to return 0 (bytes read
>>or written) instead of an error, when the buffer length is 0.
>>
>>Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
>>---
>> drivers/vhost/vdpa.c | 26 +++++++++++++++-----------
>> 1 file changed, 15 insertions(+), 11 deletions(-)
>>
>>diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
>>index 21eea2be5afa..b754c53171a7 100644
>>--- a/drivers/vhost/vdpa.c
>>+++ b/drivers/vhost/vdpa.c
>>@@ -191,9 +191,6 @@ static ssize_t vhost_vdpa_config_validate(struct vhost_vdpa *v,
>> struct vdpa_device *vdpa = v->vdpa;
>> u32 size = vdpa->config->get_config_size(vdpa);
>>- if (c->len == 0)
>>- return -EINVAL;
>>-
>> return min(c->len, size);
>> }
>>@@ -204,6 +201,7 @@ static long vhost_vdpa_get_config(struct vhost_vdpa *v,
>> struct vhost_vdpa_config config;
>> unsigned long size = offsetof(struct vhost_vdpa_config, buf);
>> ssize_t config_size;
>>+ long ret;
>> u8 *buf;
>> if (copy_from_user(&config, c, size))
>>@@ -217,15 +215,18 @@ static long vhost_vdpa_get_config(struct vhost_vdpa *v,
>> if (!buf)
>> return -ENOMEM;
>>- vdpa_get_config(vdpa, config.off, buf, config_size);
>>-
>>- if (copy_to_user(c->buf, buf, config_size)) {
>>- kvfree(buf);
>>- return -EFAULT;
>>+ ret = vdpa_get_config(vdpa, config.off, buf, config_size);
>>+ if (ret < 0) {
>>+ ret = -EFAULT;
>>+ goto out;
>> }
>>+ if (copy_to_user(c->buf, buf, config_size))
>>+ ret = -EFAULT;
>>+
>>+out:
>> kvfree(buf);
>>- return 0;
>>+ return ret;
>> }
>> static long vhost_vdpa_set_config(struct vhost_vdpa *v,
>>@@ -235,6 +236,7 @@ static long vhost_vdpa_set_config(struct vhost_vdpa *v,
>> struct vhost_vdpa_config config;
>> unsigned long size = offsetof(struct vhost_vdpa_config, buf);
>> ssize_t config_size;
>>+ long ret;
>> u8 *buf;
>> if (copy_from_user(&config, c, size))
>>@@ -248,10 +250,12 @@ static long vhost_vdpa_set_config(struct vhost_vdpa *v,
>> if (IS_ERR(buf))
>> return PTR_ERR(buf);
>>- vdpa_set_config(vdpa, config.off, buf, config_size);
>>+ ret = vdpa_set_config(vdpa, config.off, buf, config_size);
>>+ if (ret < 0)
>>+ ret = -EFAULT;
>> kvfree(buf);
>>- return 0;
>>+ return ret;
>> }
>
>
>So I wonder whether it's worth to return the number of bytes since we
>can't propogate the result to driver or driver doesn't care about
>that.

Okay, but IIUC user space application that issue VHOST_VDPA_GET_CONFIG
ioctl can use the return value.

Should we change also 'struct virtio_config_ops' to propagate this value
also to virtio drivers?

Thanks,
Stefano

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