[PATCH] drm/vkms: prime import support
Rodrigo Siqueira
rodrigosiqueiramelo at gmail.com
Tue Jul 9 13:39:18 UTC 2019
Hi Oleg,
First of all, thank you for your patch and for working in this issue.
A few comments inline.
On Thu, Jul 4, 2019 at 5:54 AM Oleg Vasilev <oleg.vasilev at intel.com> wrote:
>
> Bring dmabuf sharing through implementing prime_import_sg_table callback.
> This will help to validate userspace conformance in prime configurations
> without using any actual hardware (e.g. in the cloud).
>
> Cc: Rodrigo Siqueira <rodrigosiqueiramelo at gmail.com>
> Cc: Haneen Mohammed <hamohammed.sa at gmail.com>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Signed-off-by: Oleg Vasilev <oleg.vasilev at intel.com>
> ---
> drivers/gpu/drm/vkms/vkms_drv.c | 6 +++++
> drivers/gpu/drm/vkms/vkms_drv.h | 9 +++++++
> drivers/gpu/drm/vkms/vkms_gem.c | 46 +++++++++++++++++++++++++++++++++
> 3 files changed, 61 insertions(+)
>
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
> index cc53ef88a331..b71c16d9ca09 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.c
> +++ b/drivers/gpu/drm/vkms/vkms_drv.c
> @@ -10,6 +10,7 @@
> */
>
> #include <linux/module.h>
> +#include <linux/dma-buf.h>
Maybe I missed something, but I think you don't need to add this
include here since you already included it on vkms_gem.
> #include <drm/drm_gem.h>
> #include <drm/drm_atomic.h>
> #include <drm/drm_atomic_helper.h>
> @@ -96,6 +97,8 @@ static struct drm_driver vkms_driver = {
> .gem_vm_ops = &vkms_gem_vm_ops,
> .gem_free_object_unlocked = vkms_gem_free_object,
> .get_vblank_timestamp = vkms_get_vblank_timestamp,
> + .prime_fd_to_handle = drm_gem_prime_fd_to_handle,
> + .gem_prime_import_sg_table = vkms_prime_import_sg_table,
>
> .name = DRIVER_NAME,
> .desc = DRIVER_DESC,
> @@ -147,6 +150,9 @@ static int __init vkms_init(void)
>
> ret = drm_dev_init(&vkms_device->drm, &vkms_driver,
> &vkms_device->platform->dev);
> +
> + dma_coerce_mask_and_coherent(vkms_device->drm.dev,
> + DMA_BIT_MASK(64));
How about capture the return value from dma_coerce_mask_and_coherent()
and warn the user if something wrong happened? Something like:
ret = dma_coerce_mask_and_coherent(..);
if (ret)
DRM_WARN("Failed to set dma mask");
Additionally, I would like to suggest you move this code above
drm_dev_init() since there's a return validation of ret in the below
if.
> if (ret)
> goto out_unregister;
>
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> index 12b4db7ac641..fb15101c8f3e 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.h
> +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> @@ -126,6 +126,9 @@ struct drm_gem_object *vkms_gem_create(struct drm_device *dev,
> u32 *handle,
> u64 size);
>
> +struct vkms_gem_object *vkms_gem_create_private(struct drm_device *dev,
> + u64 size);
> +
> vm_fault_t vkms_gem_fault(struct vm_fault *vmf);
>
> int vkms_dumb_create(struct drm_file *file, struct drm_device *dev,
> @@ -137,6 +140,12 @@ int vkms_gem_vmap(struct drm_gem_object *obj);
>
> void vkms_gem_vunmap(struct drm_gem_object *obj);
>
> +/* Prime */
> +struct drm_gem_object *
> +vkms_prime_import_sg_table(struct drm_device *dev,
> + struct dma_buf_attachment *attach,
> + struct sg_table *sg);
> +
> /* CRC Support */
> const char *const *vkms_get_crc_sources(struct drm_crtc *crtc,
> size_t *count);
> diff --git a/drivers/gpu/drm/vkms/vkms_gem.c b/drivers/gpu/drm/vkms/vkms_gem.c
> index 69048e73377d..a1b837460f63 100644
> --- a/drivers/gpu/drm/vkms/vkms_gem.c
> +++ b/drivers/gpu/drm/vkms/vkms_gem.c
> @@ -1,5 +1,6 @@
> // SPDX-License-Identifier: GPL-2.0+
>
> +#include <linux/dma-buf.h>
> #include <linux/shmem_fs.h>
>
> #include "vkms_drv.h"
> @@ -117,6 +118,25 @@ struct drm_gem_object *vkms_gem_create(struct drm_device *dev,
> return &obj->gem;
> }
>
> +struct vkms_gem_object *vkms_gem_create_private(struct drm_device *dev,
> + u64 size)
> +{
I did not fully get the idea behind this function in this patch, and
it looks like this function is never invoked. Am I right or I missed
something?
> + struct vkms_gem_object *obj;
> +
> + obj = kzalloc(sizeof(*obj), GFP_KERNEL);
> +
> + if (!obj)
> + return ERR_PTR(-ENOMEM);
> +
> + size = roundup(size, PAGE_SIZE);
> +
> + drm_gem_private_object_init(dev, &obj->gem, size);
Please, correct if I'm wrong, I'm trying to understand where this
function should be placed and when it is invoked. If I correctly
understood, you want to use this function for creating a separate gem
object to be used as a private area to be shared with another device,
am I right? If I am right, I'm wondering if we could reuse or update
some of the functions available in the vkms_gem. If I am wrong, I'm
wondering if we may have synchronization problems for handling
multiples mutex for accessing pages. Could you help me here?
> +
> + mutex_init(&obj->pages_lock);
> +
> + return obj;
> +}
> +
> int vkms_dumb_create(struct drm_file *file, struct drm_device *dev,
> struct drm_mode_create_dumb *args)
> {
> @@ -217,3 +237,29 @@ int vkms_gem_vmap(struct drm_gem_object *obj)
> mutex_unlock(&vkms_obj->pages_lock);
> return ret;
> }
> +
> +struct drm_gem_object *
> +vkms_prime_import_sg_table(struct drm_device *dev,
> + struct dma_buf_attachment *attach,
> + struct sg_table *sg)
> +{
> + struct vkms_gem_object *obj;
> + int npages;
> +
> + obj = __vkms_gem_create(dev, attach->dmabuf->size);
> + if (IS_ERR(obj))
> + return ERR_CAST(obj);
> +
> + npages = PAGE_ALIGN(attach->dmabuf->size) / PAGE_SIZE;
> + DRM_DEBUG_PRIME("Importing %d pages\n", npages);
> +
> + obj->pages = kvmalloc_array(npages, sizeof(struct page *), GFP_KERNEL);
One question, why not use _get_pages() instead of using
kvmalloc_array? Use _get_pages has the advantage of already handling
some errors which may reduce the amount of code in this function.
> + if (!obj->pages) {
> + vkms_gem_free_object(&obj->gem);
> + return ERR_PTR(-ENOMEM);
> + }
> +
> + drm_prime_sg_to_page_addr_arrays(sg, obj->pages, NULL,
> + npages);
Why not add npage in the same line?
Thanks you again.
> + return &obj->gem;
> +}
> --
> 2.22.0
>
--
Rodrigo Siqueira
https://siqueira.tech
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