[PATCH V2 vfio 5/9] virtio-pci: Initialize the supported admin commands

Yishai Hadas
2023-10-30T15:27:50Z

On 29/10/2023 22:17, Michael S. Tsirkin wrote:
> On Sun, Oct 29, 2023 at 05:59:48PM +0200, Yishai Hadas wrote:
>> Initialize the supported admin commands upon activating the admin
queue.
>>
>> The supported commands are saved as part of the admin queue context, it
>> will be used by the next patches from this series.
>>
>> Note:
>> As we don't want to let upper layers to execute admin commands
before
>> that this initialization step was completed, we set ref count to 1 only
>> post of that flow and use a non ref counted version command for this
>> internal flow.
>>
>> Signed-off-by: Yishai Hadas <yishaih at nvidia.com>
>> ---
>>   drivers/virtio/virtio_pci_common.h |  1 +
>>   drivers/virtio/virtio_pci_modern.c | 77
+++++++++++++++++++++++++++++-
>>   2 files changed, 77 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/virtio/virtio_pci_common.h
b/drivers/virtio/virtio_pci_common.h
>> index a21b9ba01a60..9e07e556a51a 100644
>> --- a/drivers/virtio/virtio_pci_common.h
>> +++ b/drivers/virtio/virtio_pci_common.h
>> @@ -46,6 +46,7 @@ struct virtio_pci_admin_vq {
>>   	struct virtio_pci_vq_info info;
>>   	struct completion flush_done;
>>   	refcount_t refcount;
>> +	u64 supported_cmds;
>>   	/* Name of the admin queue: avq.$index. */
>>   	char name[10];
>>   	u16 vq_index;
>> diff --git a/drivers/virtio/virtio_pci_modern.c
b/drivers/virtio/virtio_pci_modern.c
>> index ccd7a4d9f57f..25e27aa79cab 100644
>> --- a/drivers/virtio/virtio_pci_modern.c
>> +++ b/drivers/virtio/virtio_pci_modern.c
>> @@ -19,6 +19,9 @@
>>   #define VIRTIO_RING_NO_LEGACY
>>   #include "virtio_pci_common.h"
>>
>> +static int vp_modern_admin_cmd_exec(struct virtio_device *vdev,
>> +				    struct virtio_admin_cmd *cmd);
>> +
> I don't much like forward declarations. Just order functions sensibly
> and they will not be needed.

OK, will be part of V3.

>
>>   static u64 vp_get_features(struct virtio_device *vdev)
>>   {
>>   	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
>> @@ -59,6 +62,42 @@ vp_modern_avq_set_abort(struct virtio_pci_admin_vq
*admin_vq, bool abort)
>>   	WRITE_ONCE(admin_vq->abort, abort);
>>   }
>>
>> +static void virtio_pci_admin_init_cmd_list(struct virtio_device
*virtio_dev)
>> +{
>> +	struct virtio_pci_device *vp_dev = to_vp_device(virtio_dev);
>> +	struct virtio_admin_cmd cmd = {};
>> +	struct scatterlist result_sg;
>> +	struct scatterlist data_sg;
>> +	__le64 *data;
>> +	int ret;
>> +
>> +	data = kzalloc(sizeof(*data), GFP_KERNEL);
>> +	if (!data)
>> +		return;
>> +
>> +	sg_init_one(&result_sg, data, sizeof(*data));
>> +	cmd.opcode = cpu_to_le16(VIRTIO_ADMIN_CMD_LIST_QUERY);
>> +	cmd.group_type = cpu_to_le16(VIRTIO_ADMIN_GROUP_TYPE_SRIOV);
>> +	cmd.result_sg = &result_sg;
>> +
>> +	ret = vp_modern_admin_cmd_exec(virtio_dev, &cmd);
>> +	if (ret)
>> +		goto end;
>> +
>> +	sg_init_one(&data_sg, data, sizeof(*data));
>> +	cmd.opcode = cpu_to_le16(VIRTIO_ADMIN_CMD_LIST_USE);
>> +	cmd.data_sg = &data_sg;
>> +	cmd.result_sg = NULL;
>> +
>> +	ret = vp_modern_admin_cmd_exec(virtio_dev, &cmd);
>> +	if (ret)
>> +		goto end;
>> +
>> +	vp_dev->admin_vq.supported_cmds = le64_to_cpu(*data);
>> +end:
>> +	kfree(data);
>> +}
>> +
>>   static void vp_modern_avq_activate(struct virtio_device *vdev)
>>   {
>>   	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
>> @@ -67,6 +106,7 @@ static void vp_modern_avq_activate(struct
virtio_device *vdev)
>>   	if (!virtio_has_feature(vdev, VIRTIO_F_ADMIN_VQ))
>>   		return;
>>
>> +	virtio_pci_admin_init_cmd_list(vdev);
>>   	init_completion(&admin_vq->flush_done);
>>   	refcount_set(&admin_vq->refcount, 1);
>>   	vp_modern_avq_set_abort(admin_vq, false);
>> @@ -562,6 +602,35 @@ static bool vp_get_shm_region(struct virtio_device
*vdev,
>>   	return true;
>>   }
>>
>> +static int __virtqueue_exec_admin_cmd(struct virtio_pci_admin_vq
*admin_vq,
>> +				    struct scatterlist **sgs,
>> +				    unsigned int out_num,
>> +				    unsigned int in_num,
>> +				    void *data,
>> +				    gfp_t gfp)
>> +{
>> +	struct virtqueue *vq;
>> +	int ret, len;
>> +
>> +	vq = admin_vq->info.vq;
>> +
>> +	ret = virtqueue_add_sgs(vq, sgs, out_num, in_num, data, gfp);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	if (unlikely(!virtqueue_kick(vq)))
>> +		return -EIO;
>> +
>> +	while (!virtqueue_get_buf(vq, &len) &&
>> +	       !virtqueue_is_broken(vq))
>> +		cpu_relax();
>> +
>> +	if (virtqueue_is_broken(vq))
>> +		return -EIO;
>> +
>> +	return 0;
>> +}
>> +
>
> This is tolerable I guess but it might pin the CPU for a long time.
> The difficulty is handling suprize removal well which we currently
> don't do with interrupts. I would say it's ok as is but add
> a TODO comments along the lines of /* TODO: use interrupts once these
virtqueue_is_broken */

I assume that you asked for adding the below comment before the while loop:
/* TODO use interrupts to reduce cpu cycles in the future */

Right ?

Yishai

>
>>   static int virtqueue_exec_admin_cmd(struct virtio_pci_admin_vq
*admin_vq,
>>   				    struct scatterlist **sgs,
>>   				    unsigned int out_num,
>> @@ -653,7 +722,13 @@ static int vp_modern_admin_cmd_exec(struct
virtio_device *vdev,
>>   		in_num++;
>>   	}
>>
>> -	ret = virtqueue_exec_admin_cmd(&vp_dev->admin_vq, sgs,
>> +	if (cmd->opcode == VIRTIO_ADMIN_CMD_LIST_QUERY ||
>> +	    cmd->opcode == VIRTIO_ADMIN_CMD_LIST_USE)
>> +		ret = __virtqueue_exec_admin_cmd(&vp_dev->admin_vq, sgs,
>> +				       out_num, in_num,
>> +				       sgs, GFP_KERNEL);
>> +	else
>> +		ret = virtqueue_exec_admin_cmd(&vp_dev->admin_vq, sgs,
>>   				       out_num, in_num,
>>   				       sgs, GFP_KERNEL);
>>   	if (ret) {
>> --
>> 2.27.0