linux-kernel - Re: [PATCH V2 2/4] vdpasim: customize allocation size

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Message-ID: <CAJaqyWemV8aC=MRsu_h-WuRw8bquMZnBPNGONaJ6Nz_sGNWxCg@mail.gmail.com>
Date:   Thu, 22 Dec 2022 09:22:14 +0100
From:   Eugenio Perez Martin <eperezma@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     mst@...hat.com, sgarzare@...hat.com,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 2/4] vdpasim: customize allocation size

On Thu, Dec 22, 2022 at 6:01 AM Jason Wang <jasowang@...hat.com> wrote:
>
> Allow individual simulator to customize the allocation size.
>
> Signed-off-by: Jason Wang <jasowang@...hat.com>
> ---
>  drivers/vdpa/vdpa_sim/vdpa_sim.c     | 8 ++++++--
>  drivers/vdpa/vdpa_sim/vdpa_sim.h     | 1 +
>  drivers/vdpa/vdpa_sim/vdpa_sim_blk.c | 1 +
>  drivers/vdpa/vdpa_sim/vdpa_sim_net.c | 1 +
>  4 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> index 757afef86ba0..55aaa023a6e2 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> @@ -253,7 +253,10 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
>         struct vdpa_device *vdpa;
>         struct vdpasim *vdpasim;
>         struct device *dev;
> -       int i, ret = -ENOMEM;
> +       int i, ret = -EINVAL;
> +
> +       if (!dev_attr->alloc_size)
> +               goto err_alloc;

It's weird that we need an error goto here and the next chunk of code
may return ERR_PTR(-EINVAL) directly. It's better to return directly
here in my opinion.

>
>         if (config->mask & BIT_ULL(VDPA_ATTR_DEV_FEATURES)) {
>                 if (config->device_features &
> @@ -268,9 +271,10 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
>         else
>                 ops = &vdpasim_config_ops;
>
> +       ret = -ENOMEM;

Nitpicking again,

To set ret = -ENOMEM here is weird to me, since the next failure on
__vdpa_alloc_device will override it. I'd set it right before
dma_set_mask_and_coherent, closer to its actual usage.

Actually, I'd propagate dma_set_mask_and_coherent error and set ret =
-ENOMEM right before *alloc functions, but it wasn't done that way
before this series, so not a reason to NAK to me.

Thanks!

>         vdpa = __vdpa_alloc_device(NULL, ops,
>                                    dev_attr->ngroups, dev_attr->nas,
> -                                  sizeof(struct vdpasim),
> +                                  dev_attr->alloc_size,
>                                    dev_attr->name, false);
>         if (IS_ERR(vdpa)) {
>                 ret = PTR_ERR(vdpa);
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.h b/drivers/vdpa/vdpa_sim/vdpa_sim.h
> index 0e78737dcc16..51c070a543f1 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.h
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.h
> @@ -37,6 +37,7 @@ struct vdpasim_dev_attr {
>         struct vdpa_mgmt_dev *mgmt_dev;
>         const char *name;
>         u64 supported_features;
> +       size_t alloc_size;
>         size_t config_size;
>         size_t buffer_size;
>         int nvqs;
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> index c6db1a1baf76..4f7c35f59aa5 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> @@ -378,6 +378,7 @@ static int vdpasim_blk_dev_add(struct vdpa_mgmt_dev *mdev, const char *name,
>         dev_attr.nvqs = VDPASIM_BLK_VQ_NUM;
>         dev_attr.ngroups = VDPASIM_BLK_GROUP_NUM;
>         dev_attr.nas = VDPASIM_BLK_AS_NUM;
> +       dev_attr.alloc_size = sizeof(struct vdpasim);
>         dev_attr.config_size = sizeof(struct virtio_blk_config);
>         dev_attr.get_config = vdpasim_blk_get_config;
>         dev_attr.work_fn = vdpasim_blk_work;
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_net.c b/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
> index c3cb225ea469..20cd5cdff919 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
> @@ -249,6 +249,7 @@ static int vdpasim_net_dev_add(struct vdpa_mgmt_dev *mdev, const char *name,
>         dev_attr.nvqs = VDPASIM_NET_VQ_NUM;
>         dev_attr.ngroups = VDPASIM_NET_GROUP_NUM;
>         dev_attr.nas = VDPASIM_NET_AS_NUM;
> +       dev_attr.alloc_size = sizeof(struct vdpasim);
>         dev_attr.config_size = sizeof(struct virtio_net_config);
>         dev_attr.get_config = vdpasim_net_get_config;
>         dev_attr.work_fn = vdpasim_net_work;
> --
> 2.25.1
>