by Jason Wang

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Subject: Re: [PATCH v2 12/17] vdpa_sim: add get_config callback in vdpasim_dev_attr

On 2020/11/30 下午10:14, Stefano Garzarella wrote:
> On Mon, Nov 30, 2020 at 11:25:31AM +0800, Jason Wang wrote:
>>
>> On 2020/11/26 下午10:49, Stefano Garzarella wrote:
>>> The get_config callback can be used by the device to fill the
>>> config structure.
>>> The callback will be invoked in vdpasim_get_config() before copying
>>> bytes into caller buffer.
>>>
>>> Move vDPA-net config updates from vdpasim_set_features() in the
>>> new vdpasim_net_get_config() callback.
>>>
>>> Signed-off-by: Stefano Garzarella <[email protected]>
>>> ---
>>> drivers/vdpa/vdpa_sim/vdpa_sim.c | 33 +++++++++++++++++++-------------
>>> 1 file changed, 20 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c
>>> b/drivers/vdpa/vdpa_sim/vdpa_sim.c
>>> index c07ddf6af720..8b87ce0485b6 100644
>>> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
>>> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
>>> @@ -58,6 +58,8 @@ struct vdpasim_virtqueue {
>>> #define VDPASIM_NET_FEATURES    (VDPASIM_FEATURES | \
>>>                   (1ULL << VIRTIO_NET_F_MAC))
>>> +struct vdpasim;
>>> +
>>> struct vdpasim_dev_attr {
>>>      u64 supported_features;
>>>      size_t config_size;
>>> @@ -65,6 +67,7 @@ struct vdpasim_dev_attr {
>>>      u32 id;
>>>      work_func_t work_fn;
>>> +    void (*get_config)(struct vdpasim *vdpasim, void *config);
>>> };
>>> /* State of each vdpasim device */
>>> @@ -520,8 +523,6 @@ static u64 vdpasim_get_features(struct
>>> vdpa_device *vdpa)
>>> static int vdpasim_set_features(struct vdpa_device *vdpa, u64
>>> features)
>>> {
>>>      struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
>>> -    struct virtio_net_config *config =
>>> -        (struct virtio_net_config *)vdpasim->config;
>>>      /* DMA mapping must be done by driver */
>>>      if (!(features & (1ULL << VIRTIO_F_ACCESS_PLATFORM)))
>>> @@ -529,15 +530,6 @@ static int vdpasim_set_features(struct
>>> vdpa_device *vdpa, u64 features)
>>>      vdpasim->features = features &
>>> vdpasim->dev_attr.supported_features;
>>> -    /* We generally only know whether guest is using the legacy
>>> interface
>>> -     * here, so generally that's the earliest we can set config
>>> fields.
>>> -     * Note: We actually require VIRTIO_F_ACCESS_PLATFORM above which
>>> -     * implies VIRTIO_F_VERSION_1, but let's not try to be clever
>>> here.
>>> -     */
>>> -
>>> -    config->mtu = cpu_to_vdpasim16(vdpasim, 1500);
>>> -    config->status = cpu_to_vdpasim16(vdpasim, VIRTIO_NET_S_LINK_UP);
>>> -    memcpy(config->mac, macaddr_buf, ETH_ALEN);
>>>      return 0;
>>> }
>>> @@ -593,8 +585,12 @@ static void vdpasim_get_config(struct
>>> vdpa_device *vdpa, unsigned int offset,
>>> {
>>>      struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
>>> -    if (offset + len < vdpasim->dev_attr.config_size)
>>> -        memcpy(buf, vdpasim->config + offset, len);
>>> +    if (offset + len > vdpasim->dev_attr.config_size)
>>> +        return;
>>> +
>>> +    vdpasim->dev_attr.get_config(vdpasim, vdpasim->config);
>>> +
>>> +    memcpy(buf, vdpasim->config + offset, len);
>>> }
>>
>>
>> I wonder how much value we can get from vdpasim->config consider
>> we've already had get_config() method.
>>
>> Is it possible to copy to the buffer directly here?
>
> I had thought of eliminating it too, but then I wanted to do something
> similar to what we do in QEMU (hw/virtio/virtio.c), leaving in the
> simulator core the buffer, the memory copy (handling offset and len),
> and the boundary checks.
>
> In this way each device should simply fill the entire configuration
> and we can avoid code duplication.
>
> Storing the configuration in the core may also be useful if some
> device needs to support config writes.

I think in that way we need should provide config_write().

>
> Do you think it makes sense, or is it better to move everything in the
> device?

I prefer to do that in the device but it's also fine keep what the patch
has done.

Thanks

>
> Thanks,
> Stefano
>

2020-12-01 22:35:31

by Stefano Garzarella

[permalink] [raw]

Subject: Re: [PATCH v2 12/17] vdpa_sim: add get_config callback in vdpasim_dev_attr

On Tue, Dec 01, 2020 at 11:44:19AM +0800, Jason Wang wrote:
>
>On 2020/11/30 下午10:14, Stefano Garzarella wrote:
>>On Mon, Nov 30, 2020 at 11:25:31AM +0800, Jason Wang wrote:
>>>
>>>On 2020/11/26 下午10:49, Stefano Garzarella wrote:
>>>>The get_config callback can be used by the device to fill the
>>>>config structure.
>>>>The callback will be invoked in vdpasim_get_config() before copying
>>>>bytes into caller buffer.
>>>>
>>>>Move vDPA-net config updates from vdpasim_set_features() in the
>>>>new vdpasim_net_get_config() callback.
>>>>
>>>>Signed-off-by: Stefano Garzarella <[email protected]>
>>>>---
>>>> drivers/vdpa/vdpa_sim/vdpa_sim.c | 33 +++++++++++++++++++-------------
>>>> 1 file changed, 20 insertions(+), 13 deletions(-)
>>>>
>>>>diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c
>>>>b/drivers/vdpa/vdpa_sim/vdpa_sim.c
>>>>index c07ddf6af720..8b87ce0485b6 100644
>>>>--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
>>>>+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
>>>>@@ -58,6 +58,8 @@ struct vdpasim_virtqueue {
>>>> #define VDPASIM_NET_FEATURES    (VDPASIM_FEATURES | \
>>>>                  (1ULL << VIRTIO_NET_F_MAC))
>>>>+struct vdpasim;
>>>>+
>>>> struct vdpasim_dev_attr {
>>>>     u64 supported_features;
>>>>     size_t config_size;
>>>>@@ -65,6 +67,7 @@ struct vdpasim_dev_attr {
>>>>     u32 id;
>>>>     work_func_t work_fn;
>>>>+    void (*get_config)(struct vdpasim *vdpasim, void *config);
>>>> };
>>>> /* State of each vdpasim device */
>>>>@@ -520,8 +523,6 @@ static u64 vdpasim_get_features(struct
>>>>vdpa_device *vdpa)
>>>> static int vdpasim_set_features(struct vdpa_device *vdpa, u64
>>>>features)
>>>> {
>>>>     struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
>>>>-    struct virtio_net_config *config =
>>>>-        (struct virtio_net_config *)vdpasim->config;
>>>>     /* DMA mapping must be done by driver */
>>>>     if (!(features & (1ULL << VIRTIO_F_ACCESS_PLATFORM)))
>>>>@@ -529,15 +530,6 @@ static int vdpasim_set_features(struct
>>>>vdpa_device *vdpa, u64 features)
>>>>     vdpasim->features = features &
>>>>vdpasim->dev_attr.supported_features;
>>>>-    /* We generally only know whether guest is using the legacy
>>>>interface
>>>>-     * here, so generally that's the earliest we can set config
>>>>fields.
>>>>-     * Note: We actually require VIRTIO_F_ACCESS_PLATFORM above which
>>>>-     * implies VIRTIO_F_VERSION_1, but let's not try to be
>>>>clever here.
>>>>-     */
>>>>-
>>>>-    config->mtu = cpu_to_vdpasim16(vdpasim, 1500);
>>>>-    config->status = cpu_to_vdpasim16(vdpasim, VIRTIO_NET_S_LINK_UP);
>>>>-    memcpy(config->mac, macaddr_buf, ETH_ALEN);
>>>>     return 0;
>>>> }
>>>>@@ -593,8 +585,12 @@ static void vdpasim_get_config(struct
>>>>vdpa_device *vdpa, unsigned int offset,
>>>> {
>>>>     struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
>>>>-    if (offset + len < vdpasim->dev_attr.config_size)
>>>>-        memcpy(buf, vdpasim->config + offset, len);
>>>>+    if (offset + len > vdpasim->dev_attr.config_size)
>>>>+        return;
>>>>+
>>>>+    vdpasim->dev_attr.get_config(vdpasim, vdpasim->config);
>>>>+
>>>>+    memcpy(buf, vdpasim->config + offset, len);
>>>> }
>>>
>>>
>>>I wonder how much value we can get from vdpasim->config consider
>>>we've already had get_config() method.
>>>
>>>Is it possible to copy to the buffer directly here?
>>
>>I had thought of eliminating it too, but then I wanted to do something
>>similar to what we do in QEMU (hw/virtio/virtio.c), leaving in the
>>simulator core the buffer, the memory copy (handling offset and len),
>>and the boundary checks.
>>
>>In this way each device should simply fill the entire configuration
>>and we can avoid code duplication.
>>
>>Storing the configuration in the core may also be useful if some
>>device needs to support config writes.
>
>
>I think in that way we need should provide config_write().

Yes, I'll add set_config() callback.

>
>
>>
>>Do you think it makes sense, or is it better to move everything in the
>>device?
>
>
>I prefer to do that in the device but it's also fine keep what the
>patch has done.

Okay, for now I'll keep it and add the set_config() callback, but I'm
open to move it in the device.

Thanks,
Stefano