Re: [igt-dev] [PATCH v3 i-g-t 07/15] lib/store: Refactor common store code into helper function

[John Harrison <john.c.harrison@xxxxxxxxx>]

On 1/13/2022 12:10, Matthew Brost wrote:
> On Thu, Jan 13, 2022 at 11:59:39AM -0800, John.C.Harrison@xxxxxxxxx wrote:
> > From: John Harrison <John.C.Harrison@xxxxxxxxx>
> >
> > A lot of tests use almost identical code for creating a batch buffer
> > which does a single write to memory and another is about to be added.
> > Instead, move the most generic version into a common helper function.
> > Unfortunately, the other instances are all subtly different enough to
> > make it not so trivial to try to use the helper. It could be done but
> > it is unclear if it is worth the effort at this point. This patch
> > proves the concept, if people like it enough then it can be extended.
> >
> > v2: Fix up object address vs store offset confusion (with help from
> > Zbigniew K).
> >
> > Signed-off-by: John Harrison <John.C.Harrison@xxxxxxxxx>
> > ---
> >   lib/igt_store.c             | 96 +++++++++++++++++++++++++++++++++++++
> >   lib/igt_store.h             | 12 +++++
> >   lib/meson.build             |  1 +
> >   tests/i915/gem_exec_fence.c | 77 ++---------------------------
> >   tests/i915/i915_hangman.c   |  1 +
> >   5 files changed, 115 insertions(+), 72 deletions(-)
> >   create mode 100644 lib/igt_store.c
> >   create mode 100644 lib/igt_store.h
> >
> > diff --git a/lib/igt_store.c b/lib/igt_store.c
> > new file mode 100644
> > index 000000000..42c888b55
> > --- /dev/null
> > +++ b/lib/igt_store.c
> > @@ -0,0 +1,96 @@
> > +/* SPDX-License-Identifier: MIT */
> > +/*
> > + * Copyright © 2021 Intel Corporation
> > + */
> > +
> > +#include "i915/gem_create.h"
> > +#include "igt_core.h"
> > +#include "drmtest.h"
> > +#include "igt_store.h"
> > +#include "intel_chipset.h"
> > +#include "intel_reg.h"
> > +#include "ioctl_wrappers.h"
> > +#include "lib/intel_allocator.h"
> > +
> > +/**
> > + * SECTION:igt_store_word
> > + * @short_description: Library for writing a value to memory
> > + * @title: StoreWord
> > + * @include: igt.h
> > + *
> > + * A lot of igt testcases need some mechanism for writing a value to memory
> > + * as a test that a batch buffer has executed.
> > + *
> > + * NB: Requires master for STORE_DWORD on gen4/5.
> > + */
> > +void igt_store_word(int fd, uint64_t ahnd, const intel_ctx_t *ctx,
> > +		    const struct intel_execution_engine2 *e,
> > +		    int fence, uint32_t target_handle,
> > +		    uint64_t target_gpu_addr,
> > +		    uint64_t store_offset, uint32_t store_value)
> > +{
> > +	const int SCRATCH = 0;
> > +	const int BATCH = 1;
> > +	const unsigned int gen = intel_gen(intel_get_drm_devid(fd));
> > +	struct drm_i915_gem_exec_object2 obj[2];
> > +	struct drm_i915_gem_relocation_entry reloc;
> > +	struct drm_i915_gem_execbuffer2 execbuf;
> > +	uint32_t batch[16], delta;
> > +	uint64_t bb_offset;
> > +	int i;
> > +
> > +	memset(&execbuf, 0, sizeof(execbuf));
> > +	execbuf.buffers_ptr = to_user_pointer(obj);
> > +	execbuf.buffer_count = ARRAY_SIZE(obj);
> > +	execbuf.flags = e->flags;
> > +	execbuf.rsvd1 = ctx->id;
> > +	if (fence != -1) {
> > +		execbuf.flags |= I915_EXEC_FENCE_IN;
> > +		execbuf.rsvd2 = fence;
> > +	}
> > +	if (gen < 6)
> > +		execbuf.flags |= I915_EXEC_SECURE;
> > +
> > +	memset(obj, 0, sizeof(obj));
> > +	obj[SCRATCH].handle = target_handle;
> > +
> > +	obj[BATCH].handle = gem_create(fd, 4096);
> > +	obj[BATCH].relocs_ptr = to_user_pointer(&reloc);
> > +	obj[BATCH].relocation_count = !ahnd ? 1 : 0;
> > +	bb_offset = get_offset(ahnd, obj[BATCH].handle, 4096, 0);
> > +	memset(&reloc, 0, sizeof(reloc));
> > +
> > +	i = 0;
> > +	delta = sizeof(uint32_t) * store_offset;
> Can't this overflow the delta as store_offset is a u64?
Oops.

Yeah, this code was a right mess of data words being used as addresses 
and random copies supporting 64bit or only 32bit offsets. I believe it's 
currently fine as even platforms which can theoretically support >32bits 
don't actually use it. But yes, will repost with a 64bit version of delta.

> > +	if (!ahnd) {
> > +		reloc.target_handle = obj[SCRATCH].handle;
> > +		reloc.presumed_offset = -1;
> > +		reloc.offset = sizeof(uint32_t) * (i + 1);
> > +		reloc.delta = delta;
> > +		reloc.read_domains = I915_GEM_DOMAIN_INSTRUCTION;
> > +		reloc.write_domain = I915_GEM_DOMAIN_INSTRUCTION;
> > +	} else {
> > +		obj[SCRATCH].offset = target_gpu_addr;
> > +		obj[SCRATCH].flags |= EXEC_OBJECT_PINNED | EXEC_OBJECT_WRITE;
> > +		obj[BATCH].offset = bb_offset;
> > +		obj[BATCH].flags |= EXEC_OBJECT_PINNED;
> > +	}
> > +	batch[i] = MI_STORE_DWORD_IMM | (gen < 6 ? 1 << 22 : 0);
> > +	if (gen >= 8) {
> > +		batch[++i] = target_gpu_addr + delta;
> > +		batch[++i] = (target_gpu_addr + delta) >> 32;
> This is different from the previous code, presumably this is fixing a
> bug where delta + bits 31:0 of target_gpu_addr overflows into the upper
> 32 bits?
>
> Matt
Yeah, some copies of this code were definitely broken for >32bit addresses.

John.

> > +	} else if (gen >= 4) {
> > +		batch[++i] = 0;
> > +		batch[++i] = delta;
> > +		reloc.offset += sizeof(uint32_t);
> > +	} else {
> > +		batch[i]--;
> > +		batch[++i] = delta;
> > +	}
> > +	batch[++i] = store_value;
> > +	batch[++i] = MI_BATCH_BUFFER_END;
> > +	gem_write(fd, obj[BATCH].handle, 0, batch, sizeof(batch));
> > +	gem_execbuf(fd, &execbuf);
> > +	gem_close(fd, obj[BATCH].handle);
> > +	put_offset(ahnd, obj[BATCH].handle);
> > +}
> > diff --git a/lib/igt_store.h b/lib/igt_store.h
> > new file mode 100644
> > index 000000000..5c6c8263c
> > --- /dev/null
> > +++ b/lib/igt_store.h
> > @@ -0,0 +1,12 @@
> > +/* SPDX-License-Identifier: MIT */
> > +/*
> > + * Copyright © 2021 Intel Corporation
> > + */
> > +
> > +#include "igt_gt.h"
> > +
> > +void igt_store_word(int fd, uint64_t ahnd, const intel_ctx_t *ctx,
> > +		    const struct intel_execution_engine2 *e,
> > +		    int fence, uint32_t target_handle,
> > +		    uint64_t target_gpu_addr,
> > +		    uint64_t store_offset, uint32_t store_value);
> > diff --git a/lib/meson.build b/lib/meson.build
> > index b9568a71b..3e43316d1 100644
> > --- a/lib/meson.build
> > +++ b/lib/meson.build
> > @@ -72,6 +72,7 @@ lib_sources = [
> >   	'igt_map.c',
> >   	'igt_pm.c',
> >   	'igt_dummyload.c',
> > +	'igt_store.c',
> >   	'uwildmat/uwildmat.c',
> >   	'igt_kmod.c',
> >   	'igt_panfrost.c',
> > diff --git a/tests/i915/gem_exec_fence.c b/tests/i915/gem_exec_fence.c
> > index 9a6336ce9..196236b27 100644
> > --- a/tests/i915/gem_exec_fence.c
> > +++ b/tests/i915/gem_exec_fence.c
> > @@ -28,6 +28,7 @@
> >   #include "i915/gem.h"
> >   #include "i915/gem_create.h"
> >   #include "igt.h"
> > +#include "igt_store.h"
> >   #include "igt_syncobj.h"
> >   #include "igt_sysfs.h"
> >   #include "igt_vgem.h"
> > @@ -57,74 +58,6 @@ struct sync_merge_data {
> >   #define   MI_SEMAPHORE_SAD_EQ_SDD       (4 << 12)
> >   #define   MI_SEMAPHORE_SAD_NEQ_SDD      (5 << 12)
> >   
> > -static void store(int fd, uint64_t ahnd, const intel_ctx_t *ctx,
> > -		  const struct intel_execution_engine2 *e,
> > -		  int fence, uint32_t target, uint64_t target_offset,
> > -		  unsigned offset_value)
> > -{
> > -	const int SCRATCH = 0;
> > -	const int BATCH = 1;
> > -	const unsigned int gen = intel_gen(intel_get_drm_devid(fd));
> > -	struct drm_i915_gem_exec_object2 obj[2];
> > -	struct drm_i915_gem_relocation_entry reloc;
> > -	struct drm_i915_gem_execbuffer2 execbuf;
> > -	uint32_t batch[16], delta;
> > -	uint64_t bb_offset;
> > -	int i;
> > -
> > -	memset(&execbuf, 0, sizeof(execbuf));
> > -	execbuf.buffers_ptr = to_user_pointer(obj);
> > -	execbuf.buffer_count = 2;
> > -	execbuf.flags = e->flags | I915_EXEC_FENCE_IN;
> > -	execbuf.rsvd1 = ctx->id;
> > -	execbuf.rsvd2 = fence;
> > -	if (gen < 6)
> > -		execbuf.flags |= I915_EXEC_SECURE;
> > -
> > -	memset(obj, 0, sizeof(obj));
> > -	obj[SCRATCH].handle = target;
> > -
> > -	obj[BATCH].handle = gem_create(fd, 4096);
> > -	obj[BATCH].relocs_ptr = to_user_pointer(&reloc);
> > -	obj[BATCH].relocation_count = !ahnd ? 1 : 0;
> > -	bb_offset = get_offset(ahnd, obj[BATCH].handle, 4096, 0);
> > -	memset(&reloc, 0, sizeof(reloc));
> > -
> > -	i = 0;
> > -	delta = sizeof(uint32_t) * offset_value;
> > -	if (!ahnd) {
> > -		reloc.target_handle = obj[SCRATCH].handle;
> > -		reloc.presumed_offset = -1;
> > -		reloc.offset = sizeof(uint32_t) * (i + 1);
> > -		reloc.delta = delta;
> > -		reloc.read_domains = I915_GEM_DOMAIN_INSTRUCTION;
> > -		reloc.write_domain = I915_GEM_DOMAIN_INSTRUCTION;
> > -	} else {
> > -		obj[SCRATCH].offset = target_offset;
> > -		obj[SCRATCH].flags |= EXEC_OBJECT_PINNED | EXEC_OBJECT_WRITE;
> > -		obj[BATCH].offset = bb_offset;
> > -		obj[BATCH].flags |= EXEC_OBJECT_PINNED;
> > -	}
> > -	batch[i] = MI_STORE_DWORD_IMM | (gen < 6 ? 1 << 22 : 0);
> > -	if (gen >= 8) {
> > -		batch[++i] = target_offset + delta;
> > -		batch[++i] = target_offset >> 32;
> > -	} else if (gen >= 4) {
> > -		batch[++i] = 0;
> > -		batch[++i] = delta;
> > -		reloc.offset += sizeof(uint32_t);
> > -	} else {
> > -		batch[i]--;
> > -		batch[++i] = delta;
> > -	}
> > -	batch[++i] = offset_value;
> > -	batch[++i] = MI_BATCH_BUFFER_END;
> > -	gem_write(fd, obj[BATCH].handle, 0, batch, sizeof(batch));
> > -	gem_execbuf(fd, &execbuf);
> > -	gem_close(fd, obj[BATCH].handle);
> > -	put_offset(ahnd, obj[BATCH].handle);
> > -}
> > -
> >   static bool fence_busy(int fence)
> >   {
> >   	return poll(&(struct pollfd){fence, POLLIN}, 1, 0) == 0;
> > @@ -400,13 +333,13 @@ static void test_fence_await(int fd, const intel_ctx_t *ctx,
> >   			continue;
> >   
> >   		if (flags & NONBLOCK) {
> > -			store(fd, ahnd, ctx, e2, spin->out_fence,
> > -			      scratch, scratch_offset, i);
> > +			igt_store_word(fd, ahnd, ctx, e2, spin->out_fence,
> > +				       scratch, scratch_offset, i, i);
> >   		} else {
> >   			igt_fork(child, 1) {
> >   				ahnd = get_reloc_ahnd(fd, ctx->id);
> > -				store(fd, ahnd, ctx, e2, spin->out_fence,
> > -				      scratch, scratch_offset, i);
> > +				igt_store_word(fd, ahnd, ctx, e2, spin->out_fence,
> > +					       scratch, scratch_offset, i, i);
> >   				put_ahnd(ahnd);
> >   			}
> >   		}
> > diff --git a/tests/i915/i915_hangman.c b/tests/i915/i915_hangman.c
> > index 6656b3fcd..5a0c9497c 100644
> > --- a/tests/i915/i915_hangman.c
> > +++ b/tests/i915/i915_hangman.c
> > @@ -36,6 +36,7 @@
> >   #include "i915/gem.h"
> >   #include "i915/gem_create.h"
> >   #include "igt.h"
> > +#include "igt_store.h"
> >   #include "igt_sysfs.h"
> >   #include "igt_debugfs.h"
> >   #include "sw_sync.h"
> > --
> > 2.25.1