Re: [PATCH v5 20/21] drm/tegra: Implement job submission part of new UAPI

Thierry Reding
2021-03-23T13:39:00Z

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On Mon, Jan 11, 2021 at 03:00:18PM +0200, Mikko Perttunen wrote:
> Implement the job submission IOCTL with a minimum feature set.
>
> Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
> ---
> v5:
> * Add 16K size limit to copies from userspace.
> * Guard RELOC_BLOCKLINEAR flag handling to only exist in ARM64
> to prevent oversized shift on 32-bit platforms.
> v4:
> * Remove all features that are not strictly necessary.
> * Split into two patches.
> v3:
> * Remove WRITE_RELOC. Relocations are now patched implicitly
> when patching is needed.
> * Directly call PM runtime APIs on devices instead of using
> power_on/power_off callbacks.
> * Remove incorrect mutex unlock in tegra_drm_ioctl_channel_open
> * Use XA_FLAGS_ALLOC1 instead of XA_FLAGS_ALLOC
> * Accommodate for removal of timeout field and inlining of
> syncpt_incrs array.
> * Copy entire user arrays at a time instead of going through
> elements one-by-one.
> * Implement waiting of DMA reservations.
> * Split out gather_bo implementation into a separate file.
> * Fix length parameter passed to sg_init_one in gather_bo
> * Cosmetic cleanup.
> ---
> drivers/gpu/drm/tegra/Makefile | 2 +
> drivers/gpu/drm/tegra/drm.c | 2 +
> drivers/gpu/drm/tegra/uapi/gather_bo.c | 86 +++++
> drivers/gpu/drm/tegra/uapi/gather_bo.h | 22 ++
> drivers/gpu/drm/tegra/uapi/submit.c | 428 +++++++++++++++++++++++++
> drivers/gpu/drm/tegra/uapi/submit.h | 17 +
> 6 files changed, 557 insertions(+)
> create mode 100644 drivers/gpu/drm/tegra/uapi/gather_bo.c
> create mode 100644 drivers/gpu/drm/tegra/uapi/gather_bo.h
> create mode 100644 drivers/gpu/drm/tegra/uapi/submit.c
> create mode 100644 drivers/gpu/drm/tegra/uapi/submit.h
>
> diff --git a/drivers/gpu/drm/tegra/Makefile b/drivers/gpu/drm/tegra/Makefile
> index 0abdb21b38b9..059322e88943 100644
> --- a/drivers/gpu/drm/tegra/Makefile
> +++ b/drivers/gpu/drm/tegra/Makefile
> @@ -4,6 +4,8 @@ ccflags-$(CONFIG_DRM_TEGRA_DEBUG) += -DDEBUG
> tegra-drm-y := \
> drm.o \
> uapi/uapi.o \
> + uapi/submit.o \
> + uapi/gather_bo.o \
> gem.o \
> fb.o \
> dp.o \
> diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
> index 6a51035ce33f..60eab403ae9b 100644
> --- a/drivers/gpu/drm/tegra/drm.c
> +++ b/drivers/gpu/drm/tegra/drm.c
> @@ -737,6 +737,8 @@ static const struct drm_ioctl_desc tegra_drm_ioctls[] = {
> DRM_RENDER_ALLOW),
> DRM_IOCTL_DEF_DRV(TEGRA_CHANNEL_UNMAP, tegra_drm_ioctl_channel_unmap,
> DRM_RENDER_ALLOW),
> + DRM_IOCTL_DEF_DRV(TEGRA_CHANNEL_SUBMIT, tegra_drm_ioctl_channel_submit,
> + DRM_RENDER_ALLOW),
> DRM_IOCTL_DEF_DRV(TEGRA_GEM_CREATE, tegra_drm_ioctl_gem_create,
> DRM_RENDER_ALLOW),
> DRM_IOCTL_DEF_DRV(TEGRA_GEM_MMAP, tegra_drm_ioctl_gem_mmap,
> diff --git a/drivers/gpu/drm/tegra/uapi/gather_bo.c b/drivers/gpu/drm/tegra/uapi/gather_bo.c
> new file mode 100644
> index 000000000000..b487a0d44648
> --- /dev/null
> +++ b/drivers/gpu/drm/tegra/uapi/gather_bo.c
> @@ -0,0 +1,86 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Copyright (c) 2020 NVIDIA Corporation */
> +
> +#include <linux/scatterlist.h>
> +#include <linux/slab.h>
> +
> +#include "gather_bo.h"
> +
> +static struct host1x_bo *gather_bo_get(struct host1x_bo *host_bo)
> +{
> + struct gather_bo *bo = container_of(host_bo, struct gather_bo, base);
> +
> + kref_get(&bo->ref);
> +
> + return host_bo;
> +}
> +
> +static void gather_bo_release(struct kref *ref)
> +{
> + struct gather_bo *bo = container_of(ref, struct gather_bo, ref);
> +
> + kfree(bo->gather_data);
> + kfree(bo);
> +}
> +
> +void gather_bo_put(struct host1x_bo *host_bo)
> +{
> + struct gather_bo *bo = container_of(host_bo, struct gather_bo, base);
> +
> + kref_put(&bo->ref, gather_bo_release);
> +}
> +
> +static struct sg_table *
> +gather_bo_pin(struct device *dev, struct host1x_bo *host_bo, dma_addr_t *phys)
> +{
> + struct gather_bo *bo = container_of(host_bo, struct gather_bo, base);
> + struct sg_table *sgt;
> + int err;
> +
> + if (phys) {
> + *phys = virt_to_phys(bo->gather_data);
> + return NULL;
> + }
> +
> + sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
> + if (!sgt)
> + return ERR_PTR(-ENOMEM);
> +
> + err = sg_alloc_table(sgt, 1, GFP_KERNEL);
> + if (err) {
> + kfree(sgt);
> + return ERR_PTR(err);
> + }
> +
> + sg_init_one(sgt->sgl, bo->gather_data, bo->gather_data_words*4);
> +
> + return sgt;
> +}
> +
> +static void gather_bo_unpin(struct device *dev, struct sg_table *sgt)
> +{
> + if (sgt) {
> + sg_free_table(sgt);
> + kfree(sgt);
> + }
> +}
> +
> +static void *gather_bo_mmap(struct host1x_bo *host_bo)
> +{
> + struct gather_bo *bo = container_of(host_bo, struct gather_bo, base);
> +
> + return bo->gather_data;
> +}
> +
> +static void gather_bo_munmap(struct host1x_bo *host_bo, void *addr)
> +{
> +}
> +
> +const struct host1x_bo_ops gather_bo_ops = {
> + .get = gather_bo_get,
> + .put = gather_bo_put,
> + .pin = gather_bo_pin,
> + .unpin = gather_bo_unpin,
> + .mmap = gather_bo_mmap,
> + .munmap = gather_bo_munmap,
> +};
> diff --git a/drivers/gpu/drm/tegra/uapi/gather_bo.h b/drivers/gpu/drm/tegra/uapi/gather_bo.h
> new file mode 100644
> index 000000000000..6b4c9d83ac91
> --- /dev/null
> +++ b/drivers/gpu/drm/tegra/uapi/gather_bo.h
> @@ -0,0 +1,22 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/* Copyright (c) 2020 NVIDIA Corporation */
> +
> +#ifndef _TEGRA_DRM_SUBMIT_GATHER_BO_H
> +#define _TEGRA_DRM_SUBMIT_GATHER_BO_H
> +
> +#include <linux/host1x.h>
> +#include <linux/kref.h>
> +
> +struct gather_bo {
> + struct host1x_bo base;
> +
> + struct kref ref;
> +
> + u32 *gather_data;
> + size_t gather_data_words;
> +};
> +
> +extern const struct host1x_bo_ops gather_bo_ops;
> +void gather_bo_put(struct host1x_bo *host_bo);
> +
> +#endif
> diff --git a/drivers/gpu/drm/tegra/uapi/submit.c b/drivers/gpu/drm/tegra/uapi/submit.c
> new file mode 100644
> index 000000000000..398be3065e21
> --- /dev/null
> +++ b/drivers/gpu/drm/tegra/uapi/submit.c
> @@ -0,0 +1,428 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Copyright (c) 2020 NVIDIA Corporation */
> +
> +#include <linux/dma-fence-array.h>
> +#include <linux/file.h>
> +#include <linux/host1x.h>
> +#include <linux/iommu.h>
> +#include <linux/kref.h>
> +#include <linux/list.h>
> +#include <linux/nospec.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/sync_file.h>
> +
> +#include <drm/drm_drv.h>
> +#include <drm/drm_file.h>
> +
> +#include "../uapi.h"
> +#include "../drm.h"
> +#include "../gem.h"
> +
> +#include "gather_bo.h"
> +#include "submit.h"
> +
> +static struct tegra_drm_mapping *
> +tegra_drm_mapping_get(struct tegra_drm_channel_ctx *ctx, u32 id)
> +{
> + struct tegra_drm_mapping *mapping;
> +
> + xa_lock(&ctx->mappings);
> + mapping = xa_load(&ctx->mappings, id);
> + if (mapping)
> + kref_get(&mapping->ref);
> + xa_unlock(&ctx->mappings);
> +
> + return mapping;
> +}
> +
> +static void *alloc_copy_user_array(void __user *from, size_t count, size_t size)
> +{
> + unsigned long copy_err;
> + size_t copy_len;
> + void *data;
> +
> + if (check_mul_overflow(count, size, &copy_len))
> + return ERR_PTR(-EINVAL);
> +
> + if (copy_len > 0x4000)
> + return ERR_PTR(-E2BIG);
> +
> + data = kvmalloc(copy_len, GFP_KERNEL);
> + if (!data)
> + return ERR_PTR(-ENOMEM);
> +
> + copy_err = copy_from_user(data, from, copy_len);
> + if (copy_err) {
> + kvfree(data);
> + return ERR_PTR(-EFAULT);
> + }
> +
> + return data;
> +}
> +
> +static int submit_copy_gather_data(struct drm_device *drm,
> + struct gather_bo **pbo,
> + struct drm_tegra_channel_submit *args)
> +{
> + unsigned long copy_err;
> + struct gather_bo *bo;
> + size_t copy_len;
> +
> + if (args->gather_data_words == 0) {
> + drm_info(drm, "gather_data_words can't be 0");
> + return -EINVAL;
> + }
> +
> + if (check_mul_overflow((size_t)args->gather_data_words, (size_t)4, &copy_len))
> + return -EINVAL;
> +
> + bo = kzalloc(sizeof(*bo), GFP_KERNEL);
> + if (!bo)
> + return -ENOMEM;
> +
> + kref_init(&bo->ref);
> + host1x_bo_init(&bo->base, &gather_bo_ops);
> +
> + bo->gather_data = kmalloc(copy_len, GFP_KERNEL | __GFP_NOWARN);
> + if (!bo->gather_data) {
> + kfree(bo);
> + return -ENOMEM;
> + }
> +
> + copy_err = copy_from_user(bo->gather_data,
> + u64_to_user_ptr(args->gather_data_ptr),
> + copy_len);
> + if (copy_err) {
> + kfree(bo->gather_data);
> + kfree(bo);
> + return -EFAULT;
> + }
> +
> + bo->gather_data_words = args->gather_data_words;
> +
> + *pbo = bo;
> +
> + return 0;
> +}
> +
> +static int submit_write_reloc(struct gather_bo *bo,
> + struct drm_tegra_submit_buf *buf,
> + struct tegra_drm_mapping *mapping)
> +{
> + /* TODO check that target_offset is within bounds */
> + dma_addr_t iova = mapping->iova + buf->reloc.target_offset;
> + u32 written_ptr = (u32)(iova >> buf->reloc.shift);
> +
> +#ifdef CONFIG_ARM64
> + if (buf->flags & DRM_TEGRA_SUBMIT_BUF_RELOC_BLOCKLINEAR)
> + written_ptr |= BIT(39);
> +#endif

Sorry, but this still isn't correct. written_ptr is still only 32-bits
wide, so your BIT(39) is going to get discarded even on 64-bit ARM. The
idiomatic way to do this is to make written_ptr dma_addr_t and use a
CONFIG_ARCH_DMA_ADDR_T_64BIT guard.

But even with that this looks wrong because you're OR'ing this in after
shifting by buf->reloc.shift. Doesn't that OR it in at the wrong offset?
Should you perhaps be doing this instead:

#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
if (buf->flags & DRM_TEGRA_SUBMIT_BUF_RELOC_BLOCKLINEAR)
iova |= BIT(39);
#endif

written_ptr = (u32)(iova >> buf->reloc_shift);

?

Also, on a side-note: BLOCKLINEAR really isn't the right term here. I
recently dealt with this for display (though I haven't sent out that
patch yet) and this is actually a bit that selects which sector layout
swizzling is being applied. That's independent of block linear format
and I think you can have different sector layouts irrespective of the
block linear format (though I don't think that's usually done).

That said, I wonder if a better interface here would be to reuse format
modifiers here. That would allow us to more fully describe the format of
a surface in case we ever need it, and it already includes the sector
layout information as well.

Thierry

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