[PATCH 1/2] dma-buf: add dma_fence_unwrap
Daniel Vetter
daniel at ffwll.ch
Fri Mar 25 16:00:39 UTC 2022
On Fri, Mar 25, 2022 at 01:56:23PM +0100, Christian König wrote:
> Am 25.03.22 um 11:17 schrieb Daniel Vetter:
> > On Fri, Mar 25, 2022 at 11:10:15AM +0100, Christian König wrote:
> > > Am 25.03.22 um 11:07 schrieb Daniel Vetter:
> > > > On Fri, Mar 25, 2022 at 11:03:54AM +0100, Daniel Vetter wrote:
> > > > > On Fri, Mar 11, 2022 at 12:02:43PM +0100, Christian König wrote:
> > > > > > Add a general purpose helper to deep dive into dma_fence_chain/dma_fence_array
> > > > > > structures and iterate over all the fences in them.
> > > > > >
> > > > > > This is useful when we need to flatten out all fences in those structures.
> > > > > >
> > > > > > Signed-off-by: Christian König <christian.koenig at amd.com>
> > > > > > ---
> > > > > > Documentation/driver-api/dma-buf.rst | 6 +
> > > > > > drivers/dma-buf/Makefile | 1 +
> > > > > > drivers/dma-buf/selftests.h | 1 +
> > > > > > drivers/dma-buf/st-dma-fence-unwrap.c | 279 ++++++++++++++++++++++++++
> > > > > > include/linux/dma-fence-unwrap.h | 99 +++++++++
> > > > > > 5 files changed, 386 insertions(+)
> > > > > > create mode 100644 drivers/dma-buf/st-dma-fence-unwrap.c
> > > > > > create mode 100644 include/linux/dma-fence-unwrap.h
> > > > > >
> > > > > > diff --git a/Documentation/driver-api/dma-buf.rst b/Documentation/driver-api/dma-buf.rst
> > > > > > index 2cd7db82d9fe..7209500f08c8 100644
> > > > > > --- a/Documentation/driver-api/dma-buf.rst
> > > > > > +++ b/Documentation/driver-api/dma-buf.rst
> > > > > > @@ -194,6 +194,12 @@ DMA Fence Chain
> > > > > > .. kernel-doc:: include/linux/dma-fence-chain.h
> > > > > > :internal:
> > > > > > +DMA Fence unwrap
> > > > > > +~~~~~~~~~~~~~~~~
> > > > > > +
> > > > > > +.. kernel-doc:: include/linux/dma-fence-unwrap.h
> > > > > > + :internal:
> > > > Ok I forgot one bikeshed: I'd just include this in dma-fence-chain.h and
> > > > maybe go with the dma_fence_chain_unwrap_ prefix for everything. That
> > > > makes it even more clearer that the two are meant to go together. Plus ofc
> > > > the link from struct dma_fence_chain to this iterator in the docs too.
> > > >
> > > > Or I'm just not understanding why you made this a separate thing?
> > > Well it should be used to unwrap dma_fence_array containers as well and I
> > > don't really want to add a dependency between dma_fence_chain and
> > > dma_fence_array.
> > >
> > > I've spend quite some work to keep the two containers separated and also
> > > describe the separate use cases for each.
> > >
> > > I can of course add some kerneldoc to let the chain and array documentation
> > > point to this one here.
> > Yeah I think as a general iterator they should be fine as a separate
> > thing. Also just realized that we'd need links from both array and chain
> > to this since it's for both.
>
> Done.
>
> >
> > The other thing I noticed is that we have dma_fence_chain_for_each()
> > already. Should we replace all users of that outside of dma-fence-chain.c
> > with this new thing, and move the chain specific iterator into
> > dma-fence-chain.c so that it's hidden and people don't make funny
> > accidents? Just for more safety in this maze, also ofc that's all
> > follow-up.
>
> Uff, good question. There are some valid use cases for it I think.
>
> Especially the timeline syncobj handling only want to work with chain
> structures and not with the eventually contained array.
>
> It could just be that we might want to wrap those use cases into
> dma_fence_chain helpers.
Yeah one of the drm_syncobj ones looked somewhat legit, the other is just
a dma_fence_chain_do_gc() in a trechcoat and should be wrapped in a proper
interface I guess. The driver ones looked more like they really want to
just walk fences (some iirc even hand-roll the array unwrapping further
down on their own).
> Anyway, not stuff for drm-misc-next-fixes, but going to keep that in mind.
Agreed.
-Daniel
>
> Christian.
>
> > -Daniel
> >
> >
> >
> > > Thanks,
> > > Christian.
> > >
> > > > -Daniel
> > > >
> > > > > > +
> > > > > > DMA Fence uABI/Sync File
> > > > > > ~~~~~~~~~~~~~~~~~~~~~~~~
> > > > > > diff --git a/drivers/dma-buf/Makefile b/drivers/dma-buf/Makefile
> > > > > > index 511805dbeb75..4c9eb53ba3f8 100644
> > > > > > --- a/drivers/dma-buf/Makefile
> > > > > > +++ b/drivers/dma-buf/Makefile
> > > > > > @@ -12,6 +12,7 @@ dmabuf_selftests-y := \
> > > > > > selftest.o \
> > > > > > st-dma-fence.o \
> > > > > > st-dma-fence-chain.o \
> > > > > > + st-dma-fence-unwrap.o \
> > > > > > st-dma-resv.o
> > > > > > obj-$(CONFIG_DMABUF_SELFTESTS) += dmabuf_selftests.o
> > > > > > diff --git a/drivers/dma-buf/selftests.h b/drivers/dma-buf/selftests.h
> > > > > > index 97d73aaa31da..851965867d9c 100644
> > > > > > --- a/drivers/dma-buf/selftests.h
> > > > > > +++ b/drivers/dma-buf/selftests.h
> > > > > > @@ -12,4 +12,5 @@
> > > > > > selftest(sanitycheck, __sanitycheck__) /* keep first (igt selfcheck) */
> > > > > > selftest(dma_fence, dma_fence)
> > > > > > selftest(dma_fence_chain, dma_fence_chain)
> > > > > > +selftest(dma_fence_unwrap, dma_fence_unwrap)
> > > > > > selftest(dma_resv, dma_resv)
> > > > > > diff --git a/drivers/dma-buf/st-dma-fence-unwrap.c b/drivers/dma-buf/st-dma-fence-unwrap.c
> > > > > > new file mode 100644
> > > > > > index 000000000000..d821faaebe93
> > > > > > --- /dev/null
> > > > > > +++ b/drivers/dma-buf/st-dma-fence-unwrap.c
> > > > > > @@ -0,0 +1,279 @@
> > > > > > +// SPDX-License-Identifier: MIT
> > > > > > +
> > > > > > +/*
> > > > > > + * Copyright (C) 2022 Advanced Micro Devices, Inc.
> > > > > > + */
> > > > > > +
> > > > > > +#include <linux/dma-fence-unwrap.h>
> > > > > > +#if 0
> > > > > > +#include <linux/kernel.h>
> > > > > > +#include <linux/kthread.h>
> > > > > > +#include <linux/mm.h>
> > > > > > +#include <linux/sched/signal.h>
> > > > > > +#include <linux/slab.h>
> > > > > > +#include <linux/spinlock.h>
> > > > > > +#include <linux/random.h>
> > > > > > +#endif
> > > > > > +
> > > > > > +#include "selftest.h"
> > > > > > +
> > > > > > +#define CHAIN_SZ (4 << 10)
> > > > > > +
> > > > > > +static struct kmem_cache *slab_fences;
> > > > > Your own slab feels a bit like overkill. kmalloc/kfree not good enough?
> > > > >
> > > > > > +
> > > > > > +static inline struct mock_fence {
> > > > > > + struct dma_fence base;
> > > > > > + spinlock_t lock;
> > > > > > +} *to_mock_fence(struct dma_fence *f) {
> > > > > > + return container_of(f, struct mock_fence, base);
> > > > > > +}
> > > > > > +
> > > > > > +static const char *mock_name(struct dma_fence *f)
> > > > > > +{
> > > > > > + return "mock";
> > > > > > +}
> > > > > > +
> > > > > > +static void mock_fence_release(struct dma_fence *f)
> > > > > > +{
> > > > > > + kmem_cache_free(slab_fences, to_mock_fence(f));
> > > > > > +}
> > > > > > +
> > > > > > +static const struct dma_fence_ops mock_ops = {
> > > > > > + .get_driver_name = mock_name,
> > > > > > + .get_timeline_name = mock_name,
> > > > > > + .release = mock_fence_release,
> > > > > > +};
> > > > > > +
> > > > > > +static struct dma_fence *mock_fence(void)
> > > > > > +{
> > > > > > + struct mock_fence *f;
> > > > > > +
> > > > > > + f = kmem_cache_alloc(slab_fences, GFP_KERNEL);
> > > > > > + if (!f)
> > > > > > + return NULL;
> > > > > > +
> > > > > > + spin_lock_init(&f->lock);
> > > > > > + dma_fence_init(&f->base, &mock_ops, &f->lock, 0, 0);
> > > > > > +
> > > > > > + return &f->base;
> > > > > > +}
> > > > > > +
> > > > > > +static struct dma_fence *mock_array(unsigned int num_fences, ...)
> > > > > > +{
> > > > > > + struct dma_fence_array *array;
> > > > > > + struct dma_fence **fences;
> > > > > > + va_list valist;
> > > > > > + int i;
> > > > > > +
> > > > > > + fences = kcalloc(num_fences, sizeof(*fences), GFP_KERNEL);
> > > > > > + if (!fences)
> > > > > > + return NULL;
> > > > > > +
> > > > > > + va_start(valist, num_fences);
> > > > > > + for (i = 0; i < num_fences; ++i)
> > > > > > + fences[i] = va_arg(valist, typeof(*fences));
> > > > > > + va_end(valist);
> > > > > > +
> > > > > > + array = dma_fence_array_create(num_fences, fences,
> > > > > > + dma_fence_context_alloc(1),
> > > > > > + 1, false);
> > > > > > + if (!array)
> > > > > > + goto cleanup;
> > > > > > + return &array->base;
> > > > > > +
> > > > > > +cleanup:
> > > > > > + for (i = 0; i < num_fences; ++i)
> > > > > > + dma_fence_put(fences[i]);
> > > > > > + kfree(fences);
> > > > > > + return NULL;
> > > > > > +}
> > > > > > +
> > > > > > +static struct dma_fence *mock_chain(struct dma_fence *prev,
> > > > > > + struct dma_fence *fence)
> > > > > > +{
> > > > > > + struct dma_fence_chain *f;
> > > > > > +
> > > > > > + f = dma_fence_chain_alloc();
> > > > > > + if (!f) {
> > > > > > + dma_fence_put(prev);
> > > > > > + dma_fence_put(fence);
> > > > > > + return NULL;
> > > > > > + }
> > > > > > +
> > > > > > + dma_fence_chain_init(f, prev, fence, 1);
> > > > > > + return &f->base;
> > > > > > +}
> > > > > > +
> > > > > > +static int sanitycheck(void *arg)
> > > > > > +{
> > > > > > + struct dma_fence *f, *chain, *array;
> > > > > > + int err = 0;
> > > > > > +
> > > > > > + f = mock_fence();
> > > > > > + if (!f)
> > > > > > + return -ENOMEM;
> > > > > > +
> > > > > > + array = mock_array(1, f);
> > > > > > + if (!array)
> > > > > > + return -ENOMEM;
> > > > > > +
> > > > > > + chain = mock_chain(NULL, array);
> > > > > > + if (!chain)
> > > > > > + return -ENOMEM;
> > > > > > +
> > > > > > + dma_fence_signal(f);
> > > > > > + dma_fence_put(chain);
> > > > > > + return err;
> > > > > > +}
> > > > > > +
> > > > > > +static int unwrap_array(void *arg)
> > > > > > +{
> > > > > > + struct dma_fence *fence, *f1, *f2, *array;
> > > > > > + struct dma_fence_unwrap iter;
> > > > > > + int err = 0;
> > > > > > +
> > > > > > + f1 = mock_fence();
> > > > > > + if (!f1)
> > > > > > + return -ENOMEM;
> > > > > > +
> > > > > > + f2 = mock_fence();
> > > > > > + if (!f2) {
> > > > > > + dma_fence_put(f1);
> > > > > > + return -ENOMEM;
> > > > > > + }
> > > > > > +
> > > > > > + array = mock_array(2, f1, f2);
> > > > > > + if (!array)
> > > > > > + return -ENOMEM;
> > > > > > +
> > > > > > + dma_fence_unwrap_for_each(fence, &iter, array) {
> > > > > > + if (fence == f1) {
> > > > > > + f1 = NULL;
> > > > > > + } else if (fence == f2) {
> > > > > > + f2 = NULL;
> > > > > > + } else {
> > > > > > + pr_err("Unexpected fence!\n");
> > > > > > + err = -EINVAL;
> > > > > > + }
> > > > > > + }
> > > > > > +
> > > > > > + if (f1 || f2) {
> > > > > > + pr_err("Not all fences seen!\n");
> > > > > > + err = -EINVAL;
> > > > > > + }
> > > > > > +
> > > > > > + dma_fence_signal(f1);
> > > > > > + dma_fence_signal(f2);
> > > > > > + dma_fence_put(array);
> > > > > > + return 0;
> > > > > > +}
> > > > > > +
> > > > > > +static int unwrap_chain(void *arg)
> > > > > > +{
> > > > > > + struct dma_fence *fence, *f1, *f2, *chain;
> > > > > > + struct dma_fence_unwrap iter;
> > > > > > + int err = 0;
> > > > > > +
> > > > > > + f1 = mock_fence();
> > > > > > + if (!f1)
> > > > > > + return -ENOMEM;
> > > > > > +
> > > > > > + f2 = mock_fence();
> > > > > > + if (!f2) {
> > > > > > + dma_fence_put(f1);
> > > > > > + return -ENOMEM;
> > > > > > + }
> > > > > > +
> > > > > > + chain = mock_chain(f1, f2);
> > > > > > + if (!chain)
> > > > > > + return -ENOMEM;
> > > > > > +
> > > > > > + dma_fence_unwrap_for_each(fence, &iter, chain) {
> > > > > > + if (fence == f1) {
> > > > > > + f1 = NULL;
> > > > > > + } else if (fence == f2) {
> > > > > > + f2 = NULL;
> > > > > > + } else {
> > > > > > + pr_err("Unexpected fence!\n");
> > > > > > + err = -EINVAL;
> > > > > > + }
> > > > > > + }
> > > > > > +
> > > > > > + if (f1 || f2) {
> > > > > > + pr_err("Not all fences seen!\n");
> > > > > > + err = -EINVAL;
> > > > > > + }
> > > > > > +
> > > > > > + dma_fence_signal(f1);
> > > > > > + dma_fence_signal(f2);
> > > > > > + dma_fence_put(chain);
> > > > > > + return 0;
> > > > > > +}
> > > > > > +
> > > > > > +static int unwrap_chain_array(void *arg)
> > > > > > +{
> > > > > > + struct dma_fence *fence, *f1, *f2, *array, *chain;
> > > > > > + struct dma_fence_unwrap iter;
> > > > > > + int err = 0;
> > > > > > +
> > > > > > + f1 = mock_fence();
> > > > > > + if (!f1)
> > > > > > + return -ENOMEM;
> > > > > > +
> > > > > > + f2 = mock_fence();
> > > > > > + if (!f2) {
> > > > > > + dma_fence_put(f1);
> > > > > > + return -ENOMEM;
> > > > > > + }
> > > > > > +
> > > > > > + array = mock_array(2, f1, f2);
> > > > > > + if (!array)
> > > > > > + return -ENOMEM;
> > > > > > +
> > > > > > + chain = mock_chain(NULL, array);
> > > > > > + if (!chain)
> > > > > > + return -ENOMEM;
> > > > > > +
> > > > > > + dma_fence_unwrap_for_each(fence, &iter, chain) {
> > > > > > + if (fence == f1) {
> > > > > > + f1 = NULL;
> > > > > > + } else if (fence == f2) {
> > > > > > + f2 = NULL;
> > > > > > + } else {
> > > > > > + pr_err("Unexpected fence!\n");
> > > > > > + err = -EINVAL;
> > > > > > + }
> > > > > > + }
> > > > > > +
> > > > > > + if (f1 || f2) {
> > > > > > + pr_err("Not all fences seen!\n");
> > > > > > + err = -EINVAL;
> > > > > > + }
> > > > > > +
> > > > > > + dma_fence_signal(f1);
> > > > > > + dma_fence_signal(f2);
> > > > > > + dma_fence_put(chain);
> > > > > > + return 0;
> > > > > > +}
> > > > > > +
> > > > > > +int dma_fence_unwrap(void)
> > > > > > +{
> > > > > > + static const struct subtest tests[] = {
> > > > > > + SUBTEST(sanitycheck),
> > > > > > + SUBTEST(unwrap_array),
> > > > > > + SUBTEST(unwrap_chain),
> > > > > > + SUBTEST(unwrap_chain_array),
> > > > > > + };
> > > > > > + int ret;
> > > > > > +
> > > > > > + slab_fences = KMEM_CACHE(mock_fence,
> > > > > > + SLAB_TYPESAFE_BY_RCU |
> > > > > > + SLAB_HWCACHE_ALIGN);
> > > > > > + if (!slab_fences)
> > > > > > + return -ENOMEM;
> > > > > > +
> > > > > > + ret = subtests(tests, NULL);
> > > > > > +
> > > > > > + kmem_cache_destroy(slab_fences);
> > > > > > + return ret;
> > > > > > +}
> > > > > > diff --git a/include/linux/dma-fence-unwrap.h b/include/linux/dma-fence-unwrap.h
> > > > > > new file mode 100644
> > > > > > index 000000000000..54963df00c98
> > > > > > --- /dev/null
> > > > > > +++ b/include/linux/dma-fence-unwrap.h
> > > > > > @@ -0,0 +1,99 @@
> > > > > > +/* SPDX-License-Identifier: GPL-2.0-only */
> > > > > > +/*
> > > > > > + * fence-chain: chain fences together in a timeline
> > > > > > + *
> > > > > > + * Copyright (C) 2022 Advanced Micro Devices, Inc.
> > > > > > + * Authors:
> > > > > > + * Christian König <christian.koenig at amd.com>
> > > > > > + */
> > > > > > +
> > > > > > +#ifndef __LINUX_DMA_FENCE_UNWRAP_H
> > > > > > +#define __LINUX_DMA_FENCE_UNWRAP_H
> > > > > > +
> > > > > > +#include <linux/dma-fence-chain.h>
> > > > > > +#include <linux/dma-fence-array.h>
> > > > > > +
> > > > > > +/**
> > > > > > + * struct dma_fence_unwrap - cursor into the container structure
> > > > > I think adding "This should be used together with
> > > > > dma_fence_unwrap_for_each() iterator macro." would be nice here. I just
> > > > > like links :-)
> > > > >
> > > > > > + */
> > > > > > +struct dma_fence_unwrap {
> > > > > > + /**
> > > > > > + * @chain: potential dma_fence_chain, but can be other fence as well
> > > > > > + */
> > > > > > + struct dma_fence *chain;
> > > > > > + /**
> > > > > > + * @array: potential dma_fence_array, but can be other fence as well
> > > > > > + */
> > > > > > + struct dma_fence *array;
> > > > > > + /**
> > > > > > + * @index: last returned index if @array is really a dma_fence_array
> > > > > > + */
> > > > > > + unsigned int index;
> > > > > > +};
> > > > > > +
> > > > > > +/**
> > > > > > + * dma_fence_unwrap_array - helper to unwrap dma_fence_arrays
> > > > > > + * @cursor: cursor to initialize
> > > > > > + *
> > > > > > + * Helper function to unwrap dma_fence_array containers, don't touch directly.
> > > > > > + * Use dma_fence_unwrap_first/next instead.
> > > > > > + */
> > > > > > +static inline struct dma_fence *
> > > > > > +dma_fence_unwrap_array(struct dma_fence_unwrap * cursor)
> > > > > Since this is a helper that no one should call I'd give it a __ prefix and
> > > > > drop the kerneldoc. Documenting stuff that people shouldn't use is
> > > > > confusing :-)
> > > > >
> > > > > > +{
> > > > > > + cursor->array = dma_fence_chain_contained(cursor->chain);
> > > > > > + cursor->index = 0;
> > > > > > + return dma_fence_array_first(cursor->array);
> > > > > > +}
> > > > > > +
> > > > > > +/**
> > > > > > + * dma_fence_unwrap_first - return the first fence from fence containers
> > > > > > + * @head: the entrypoint into the containers
> > > > > > + * @cursor: current position inside the containers
> > > > > > + *
> > > > > > + * Unwraps potential dma_fence_chain/dma_fence_array containers and return the
> > > > > > + * first fence.
> > > > > > + */
> > > > > > +static inline struct dma_fence *
> > > > > > +dma_fence_unwrap_first(struct dma_fence *head, struct dma_fence_unwrap *cursor)
> > > > > > +{
> > > > > > + cursor->chain = dma_fence_get(head);
> > > > > > + return dma_fence_unwrap_array(cursor);
> > > > > > +}
> > > > > > +
> > > > > > +/**
> > > > > > + * dma_fence_unwrap_next - return the next fence from a fence containers
> > > > > > + * @cursor: current position inside the containers
> > > > > > + *
> > > > > > + * Continue unwrapping the dma_fence_chain/dma_fence_array containers and return
> > > > > > + * the next fence from them.
> > > > > > + */
> > > > > > +static inline struct dma_fence *
> > > > > > +dma_fence_unwrap_next(struct dma_fence_unwrap *cursor)
> > > > > > +{
> > > > > > + struct dma_fence *tmp;
> > > > > > +
> > > > > > + ++cursor->index;
> > > > > > + tmp = dma_fence_array_next(cursor->array, cursor->index);
> > > > > > + if (tmp)
> > > > > > + return tmp;
> > > > > > +
> > > > > > + cursor->chain = dma_fence_chain_walk(cursor->chain);
> > > > > > + return dma_fence_unwrap_array(cursor);
> > > > > > +}
> > > > > > +
> > > > > > +/**
> > > > > > + * dma_fence_unwrap_for_each - iterate over all fences in containers
> > > > > > + * @fence: current fence
> > > > > > + * @cursor: current position inside the containers
> > > > > > + * @head: starting point for the iterator
> > > > > > + *
> > > > > > + * Unwrap dma_fence_chain and dma_fence_array containers and deep dive into all
> > > > > > + * potential fences in them. If @head is just a normal fence only that one is
> > > > > > + * returned.
> > > > > > + */
> > > > > > +#define dma_fence_unwrap_for_each(fence, cursor, head) \
> > > > > > + for (fence = dma_fence_unwrap_first(head, cursor); fence; \
> > > > > > + fence = dma_fence_unwrap_next(cursor))
> > > > > > +
> > > > > > +#endif
> > > > > I think it'd be really good to add a small paragraph to struct
> > > > > dma_fence_chain that this macro and iterator should be used for walking
> > > > > over all fences in a chain, including any fence arrays or anything like
> > > > > that.
> > > > >
> > > > > With the bikesheds addressed:
> > > > >
> > > > > Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> > > > >
> > > > > > --
> > > > > > 2.25.1
> > > > > >
> > > > > --
> > > > > Daniel Vetter
> > > > > Software Engineer, Intel Corporation
> > > > > https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fblog.ffwll.ch%2F&data=04%7C01%7Cchristian.koenig%40amd.com%7Caa747083900b451d359308da0e4745e3%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637837996532802687%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=Jts5%2BObWJHeUG4oy2biwj5Bf3PKkMrYU%2F0EihvQRNuY%3D&reserved=0
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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