Re: [igt-dev] [PATCH i-g-t] i915/gem_workarounds: Verify regs directly

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> It seems like the HW validator is getting better at preventing our
> snooping of system registers from non-privileged batches! If we can't
> use SRM, let's probe the register directly through mmio, making sure we
> have the context spinning on the GPU first.
>
> v2: Hold forcewake just in case the spinning batch isn't enough to
> justify our register access.
>

If I recall correctly, either of them separately didn't
work. And there was delay after grabbing the fw before
the register contents appeared. Don't remember the gen tho.

> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110544
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Matthew Auld <matthew.william.auld@gmail.com>
> ---
>  tests/i915/gem_workarounds.c | 88 +++++++-----------------------------
>  1 file changed, 17 insertions(+), 71 deletions(-)
>
> diff --git a/tests/i915/gem_workarounds.c b/tests/i915/gem_workarounds.c
> index 44e3dce8a..2767b04d7 100644
> --- a/tests/i915/gem_workarounds.c
> +++ b/tests/i915/gem_workarounds.c
> @@ -80,70 +80,27 @@ static bool write_only(const uint32_t addr)
>  	return false;
>  }
>  
> -#define MI_STORE_REGISTER_MEM (0x24 << 23)
> -
> -static int workaround_fail_count(int fd, uint32_t ctx)
> +static int workaround_fail_count(int i915, uint32_t ctx)
>  {
> -	struct drm_i915_gem_exec_object2 obj[2];
> -	struct drm_i915_gem_relocation_entry *reloc;
> -	struct drm_i915_gem_execbuffer2 execbuf;
> -	uint32_t result_sz, batch_sz;
> -	uint32_t *base, *out;
> -	int fail_count = 0;
> -
> -	reloc = calloc(num_wa_regs, sizeof(*reloc));
> -	igt_assert(reloc);
> -
> -	result_sz = 4 * num_wa_regs;
> -	result_sz = PAGE_ALIGN(result_sz);
> -
> -	batch_sz = 16 * num_wa_regs + 4;
> -	batch_sz = PAGE_ALIGN(batch_sz);
> -
> -	memset(obj, 0, sizeof(obj));
> -	obj[0].handle = gem_create(fd, result_sz);
> -	gem_set_caching(fd, obj[0].handle, I915_CACHING_CACHED);
> -	obj[1].handle = gem_create(fd, batch_sz);
> -	obj[1].relocs_ptr = to_user_pointer(reloc);
> -	obj[1].relocation_count = num_wa_regs;
> -
> -	out = base = gem_mmap__cpu(fd, obj[1].handle, 0, batch_sz, PROT_WRITE);
> -	for (int i = 0; i < num_wa_regs; i++) {
> -		*out++ = MI_STORE_REGISTER_MEM | ((gen >= 8 ? 4 : 2) - 2);
> -		*out++ = wa_regs[i].addr;
> -		reloc[i].target_handle = obj[0].handle;
> -		reloc[i].offset = (out - base) * sizeof(*out);
> -		reloc[i].delta = i * sizeof(uint32_t);
> -		reloc[i].read_domains = I915_GEM_DOMAIN_INSTRUCTION;
> -		reloc[i].write_domain = I915_GEM_DOMAIN_INSTRUCTION;
> -		*out++ = reloc[i].delta;
> -		if (gen >= 8)
> -			*out++ = 0;
> -	}
> -	*out++ = MI_BATCH_BUFFER_END;
> -	munmap(base, batch_sz);
> +	igt_spin_t *spin;
> +	int fw, fail = 0;
>  
> -	memset(&execbuf, 0, sizeof(execbuf));
> -	execbuf.buffers_ptr = to_user_pointer(obj);
> -	execbuf.buffer_count = 2;
> -	execbuf.rsvd1 = ctx;
> -	gem_execbuf(fd, &execbuf);
> +	spin = igt_spin_new(i915, .ctx = ctx, .flags = IGT_SPIN_POLL_RUN);
> +	igt_spin_busywait_until_started(spin);
>  
> -	gem_set_domain(fd, obj[0].handle, I915_GEM_DOMAIN_CPU, 0);
> -
> -	igt_debug("Address\tval\t\tmask\t\tread\t\tresult\n");
> -
> -	out = gem_mmap__cpu(fd, obj[0].handle, 0, result_sz, PROT_READ);
> +	fw = igt_open_forcewake_handle(i915);

assert that it went fine?

Perhaps both will now do the trick. But if it fails
get the forcewake before spinner so you get more delay.

>  	for (int i = 0; i < num_wa_regs; i++) {
> +		uint32_t value =
> +			*(uint32_t *)(igt_global_mmio + wa_regs[i].addr);

const might have been warranted.

Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>

>  		const bool ok =
>  			(wa_regs[i].value & wa_regs[i].mask) ==
> -			(out[i] & wa_regs[i].mask);
> +			(value & wa_regs[i].mask);
>  		char buf[80];
>  
>  		snprintf(buf, sizeof(buf),
>  			 "0x%05X\t0x%08X\t0x%08X\t0x%08X",
>  			 wa_regs[i].addr, wa_regs[i].value, wa_regs[i].mask,
> -			 out[i]);
> +			 value);
>  
>  		if (ok) {
>  			igt_debug("%s\tOK\n", buf);
> @@ -151,27 +108,14 @@ static int workaround_fail_count(int fd, uint32_t ctx)
>  			igt_debug("%s\tIGNORED (w/o)\n", buf);
>  		} else {
>  			igt_warn("%s\tFAIL\n", buf);
> -			fail_count++;
> +			fail++;
>  		}
>  	}
> -	munmap(out, result_sz);
> +	close(fw);
>  
> -	gem_close(fd, obj[1].handle);
> -	gem_close(fd, obj[0].handle);
> -	free(reloc);
> +	igt_spin_free(i915, spin);
>  
> -	return fail_count;
> -}
> -
> -static int reopen(int fd)
> -{
> -	char path[256];
> -
> -	snprintf(path, sizeof(path), "/proc/self/fd/%d", fd);
> -	fd = open(path, O_RDWR);
> -	igt_assert_lte(0, fd);
> -
> -	return fd;
> +	return fail;
>  }
>  
>  #define CONTEXT 0x1
> @@ -181,7 +125,7 @@ static void check_workarounds(int fd, enum operation op, unsigned int flags)
>  	uint32_t ctx = 0;
>  
>  	if (flags & FD)
> -		fd = reopen(fd);
> +		fd = gem_reopen_driver(fd);
>  
>  	if (flags & CONTEXT) {
>  		gem_require_contexts(fd);
> @@ -252,6 +196,8 @@ igt_main
>  		device = drm_open_driver(DRIVER_INTEL);
>  		igt_require_gem(device);
>  
> +		intel_mmio_use_pci_bar(intel_get_pci_device());
> +
>  		gen = intel_gen(intel_get_drm_devid(device));
>  
>  		fd = igt_debugfs_open(device, "i915_wa_registers", O_RDONLY);
> -- 
> 2.20.1
>
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