[Intel-gfx] [PATCH] gen8_ppgtt: Use correct huge page manager for MTL

[Cavitt, Jonathan]

-----Original Message-----
From: Auld, Matthew <matthew.auld at intel.com> 
Sent: Tuesday, February 21, 2023 8:33 AM
To: Cavitt, Jonathan <jonathan.cavitt at intel.com>
Cc: Dutt, Sudeep <sudeep.dutt at intel.com>; Siddiqui, Ayaz A <ayaz.siddiqui at intel.com>; intel-gfx at lists.freedesktop.org
Subject: Re: [PATCH] gen8_ppgtt: Use correct huge page manager for MTL
> 
> On 21/02/2023 16:28, Cavitt, Jonathan wrote:
> > -----Original Message-----
> > From: Auld, Matthew <matthew.auld at intel.com>
> > Sent: Tuesday, February 21, 2023 8:06 AM
> > To: Cavitt, Jonathan <jonathan.cavitt at intel.com>; intel-gfx at lists.freedesktop.org
> > Cc: Dutt, Sudeep <sudeep.dutt at intel.com>; Siddiqui, Ayaz A <ayaz.siddiqui at intel.com>
> > Subject: Re: [PATCH] gen8_ppgtt: Use correct huge page manager for MTL
> >>
> >> On 17/02/2023 19:18, Jonathan Cavitt wrote:
> >>> MTL currently uses gen8_ppgtt_insert_huge when managing huge pages.  This is because
> >>> MTL reports as not supporting 64K pages, or more accurately, the system that reports
> >>> whether a platform has 64K pages reports false for MTL.  This is only half correct,
> >>> as the 64K page support reporting system only cares about 64K page support for LMEM,
> >>> which MTL doesn't have.
> >>>
> >>> MTL should be using xehpsdv_ppgtt_insert_huge.  However, simply changing over to
> >>> using that manager doesn't resolve the issue because MTL is expecting the virtual
> >>> address space for the page table to be flushed after initialization, so we must also
> >>> add a flush statement there.
> >>>
> >>> Signed-off-by: Jonathan Cavitt <jonathan.cavitt at intel.com>
> >> Reviewed-by: Matthew Auld <matthew.auld at intel.com>
> >>
> >> Although it looks like the hugepage mock tests are failing with this. I
> >> assume the mock device just uses some "max" gen version or so, which now
> >> triggers this path. Any ideas for that?
> > 
> > With this patch applied, multiple calls to the hugepages live selftest result in a kernel panic.
> > If the mock tests are run immediately after the live ones, that would explain this behavior.
> > I was informed when this was initially debugged that the error was a known IOMMU issue
> > rather than some novel regression, though it's hard to tell if that was just hopeful optimism
> > or not at this point.
> 
> In the test results we now get:
> 
> 6> [183.420316] i915: Running 
> i915_gem_huge_page_mock_selftests/igt_mock_exhaust_device_supported_pages
> <6> [183.436978] i915: Running 
> i915_gem_huge_page_mock_selftests/igt_mock_memory_region_huge_pages
> <6> [183.445777] i915: Running 
> i915_gem_huge_page_mock_selftests/igt_mock_ppgtt_misaligned_dma
> <6> [183.904531] i915: Running 
> i915_gem_huge_page_mock_selftests/igt_mock_ppgtt_huge_fill
> <3> [183.912658] gtt=69632, expected=4096, size=69632, single=yes
> <3> [183.912784] i915/i915_gem_huge_page_mock_selftests: 
> igt_mock_ppgtt_huge_fill failed with error -22

                if (expected_gtt & I915_GTT_PAGE_SIZE_4K)
                        expected_gtt &= ~I915_GTT_PAGE_SIZE_64K;

I don't know why we're doing that to expected_gtt, but that seems to be the cause of the
problem in this case.
-Jonathan Cavitt

> 
> I didn't look any deeper than that though. Note that this a just a 
> mock/fake device. I don't think its IOMMU related.
> 
> > -Jonathan Cavitt
> > 
> >>
> >>> ---
> >>>    drivers/gpu/drm/i915/gt/gen8_ppgtt.c | 3 ++-
> >>>    1 file changed, 2 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
> >>> index 4daaa6f55668..9c571185395f 100644
> >>> --- a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
> >>> +++ b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
> >>> @@ -570,6 +570,7 @@ xehpsdv_ppgtt_insert_huge(struct i915_address_space *vm,
> >>>    			}
> >>>    		} while (rem >= page_size && index < max);
> >>>    
> >>> +		drm_clflush_virt_range(vaddr, PAGE_SIZE);
> >>>    		vma_res->page_sizes_gtt |= page_size;
> >>>    	} while (iter->sg && sg_dma_len(iter->sg));
> >>>    }
> >>> @@ -707,7 +708,7 @@ static void gen8_ppgtt_insert(struct i915_address_space *vm,
> >>>    	struct sgt_dma iter = sgt_dma(vma_res);
> >>>    
> >>>    	if (vma_res->bi.page_sizes.sg > I915_GTT_PAGE_SIZE) {
> >>> -		if (HAS_64K_PAGES(vm->i915))
> >>> +		if (GRAPHICS_VER_FULL(vm->i915) >= IP_VER(12, 50))
> >>>    			xehpsdv_ppgtt_insert_huge(vm, vma_res, &iter, cache_level, flags);
> >>>    		else
> >>>    			gen8_ppgtt_insert_huge(vm, vma_res, &iter, cache_level, flags);
> >>
>