Messages in this thread | | | Subject | Re: [RFC PATCH 10/10] vhost/vdpa: return configuration bytes read and written to user space | From | Jason Wang <> | Date | Mon, 8 Mar 2021 11:59:12 +0800 |
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On 2021/3/5 4:37 下午, Stefano Garzarella wrote: > On Thu, Mar 04, 2021 at 04:31:22PM +0800, Jason Wang wrote: >> >> On 2021/3/2 10:06 下午, Stefano Garzarella wrote: >>> 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. >> >> >> Yes, but it looks to it's too late to change since it's a userspace >> noticble behaviour. > > Yeah, this is a good point. > I looked at QEMU and we only check if the value is not negative, so it > should work, but for other applications it could be a real change. > > Do we leave it as is?
Yes, I think we'd better be conservative here.
Thanks
> >> >> >>> >>> Should we change also 'struct virtio_config_ops' to propagate this >>> value also to virtio drivers? >> >> >> I think not, the reason is the driver doesn't expect the get()/set() >> can fail... > > Got it. > > Thanks, > Stefano >
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