On Fri, Nov 12, 2021 at 05:42:28PM -0800, Michael Cheng wrote:
> Thanks for the feed back! I feel like using something name GEN6 or BYT for a
> platform that's not GEN6 or BYT could be a bit confusing, that's why we
> decided to go with something more generic. I do agree I need to cite the
> bspec more. Ill wait for more feedback before I send a new revision out.
In general that's the pattern that i915 tries to use --- we name
functions, macros, etc. after the first platform or generation that they
apply to and then continue to use them on all subsequent platforms until
the hardware changes again and we need a new version. E.g., we're still
calling "gen8_ppgtt_create" to create our PPGTTs on the latest
platforms, even though we're well past gen8 at this point.
Matt
>
> On 2021-11-12 5:31 p.m., Matt Roper wrote:
> > On Fri, Nov 12, 2021 at 05:28:09PM -0800, Matt Roper wrote:
> > > On Wed, Nov 10, 2021 at 04:45:47PM -0800, Michael Cheng wrote:
> > > > Certain functions within i915 uses macros that are defined for
> > > > specific architectures by the mmu, such as _PAGE_RW and _PAGE_PRESENT
> > > > (Some architectures don't even have these macros defined, like ARM64).
> > > >
> > > > Instead of re-using bits defined for the CPU, we should use bits
> > > > defined for i915. This patch introduces two new macros,
> > > > I915_PAGE_PRESENT and I915_PAGE_RW, to check for bits 0 and 1 and, to
> > > > replace all occurrences of _PAGE_RW and _PAGE_PRESENT within i915.
> > > On older platforms we already had our own definition of GEN6_PTE_VALID
> > > (the spec uses "present" and "valid" interchangeably) which we were
> > > using to encode our ggtt ptes up through HSW; it might be better to go
> > > back to using that rather than adding a new define.
> > >
> > > It looks like BYT is when the writable bit showed up, and we did add a
> > > new define there (BYT_PTE_WRITEABLE), but on the next platform (BDW) we
> > > switched over to using the CPU page table flags instead and never used
> > > it again. So we could probably replace _PAGE_RW with BYT_PTE_WRITEABLE
> > > as well.
> > Okay, I should have looked at the rest of the series before reviewing
> > the first patch; it looks like your next two patches replace
> > GEN6_PTE_VALID and BYT_PTE_WRITEABLE with the new definitions here. I
> > still think it might be preferable to reuse the existing macros (which
> > also help clarify the platforms that those bits first showed up in the
> > PTE on) rather than replacing them with new macros, but I don't feel
> > super strongly about it if other reviewers feel differently.
> >
> >
> > Matt
> >
> > > > Looking at the bspecs for pre gen 12 and gen 12, bit 0 and 1 are the
> > > > same throughout the generations.
> > > This last sentence seems a bit confusing --- it's true that bit 0 has
> > > always been a present/valid flag, but bit 1 wasn't a writable bit until
> > > BYT; there just wasn't a writable bit at all (e.g., bspec page 229).
> > >
> > > It might be worth tossing a few bspec references on the commit message
> > > here, just for future reference. E.g.,
> > >
> > > Bspec: 253, 45039
> > >
> > >
> > > Matt
> > >
> > > > Signed-off-by: Michael Cheng <michael.cheng@xxxxxxxxx>
> > > > ---
> > > > drivers/gpu/drm/i915/gt/gen8_ppgtt.c | 6 +++---
> > > > drivers/gpu/drm/i915/gt/intel_ggtt.c | 2 +-
> > > > drivers/gpu/drm/i915/gt/intel_gtt.h | 3 +++
> > > > drivers/gpu/drm/i915/gvt/gtt.c | 12 ++++++------
> > > > 4 files changed, 13 insertions(+), 10 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
> > > > index 9966e9dc5218..f89b50ffc286 100644
> > > > --- a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
> > > > +++ b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
> > > > @@ -18,7 +18,7 @@
> > > > static u64 gen8_pde_encode(const dma_addr_t addr,
> > > > const enum i915_cache_level level)
> > > > {
> > > > - u64 pde = addr | _PAGE_PRESENT | _PAGE_RW;
> > > > + u64 pde = addr | I915_PAGE_PRESENT | I915_PAGE_RW;
> > > > if (level != I915_CACHE_NONE)
> > > > pde |= PPAT_CACHED_PDE;
> > > > @@ -32,10 +32,10 @@ static u64 gen8_pte_encode(dma_addr_t addr,
> > > > enum i915_cache_level level,
> > > > u32 flags)
> > > > {
> > > > - gen8_pte_t pte = addr | _PAGE_PRESENT | _PAGE_RW;
> > > > + gen8_pte_t pte = addr | I915_PAGE_PRESENT | I915_PAGE_RW;
> > > > if (unlikely(flags & PTE_READ_ONLY))
> > > > - pte &= ~_PAGE_RW;
> > > > + pte &= ~I915_PAGE_RW;
> > > > if (flags & PTE_LM)
> > > > pte |= GEN12_PPGTT_PTE_LM;
> > > > diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt.c b/drivers/gpu/drm/i915/gt/intel_ggtt.c
> > > > index 1fb4a03d7ac3..3f8e1ee0fbfa 100644
> > > > --- a/drivers/gpu/drm/i915/gt/intel_ggtt.c
> > > > +++ b/drivers/gpu/drm/i915/gt/intel_ggtt.c
> > > > @@ -207,7 +207,7 @@ u64 gen8_ggtt_pte_encode(dma_addr_t addr,
> > > > enum i915_cache_level level,
> > > > u32 flags)
> > > > {
> > > > - gen8_pte_t pte = addr | _PAGE_PRESENT;
> > > > + gen8_pte_t pte = addr | I915_PAGE_PRESENT;
> > > > if (flags & PTE_LM)
> > > > pte |= GEN12_GGTT_PTE_LM;
> > > > diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.h b/drivers/gpu/drm/i915/gt/intel_gtt.h
> > > > index dfeaef680aac..fba9c0c18f4a 100644
> > > > --- a/drivers/gpu/drm/i915/gt/intel_gtt.h
> > > > +++ b/drivers/gpu/drm/i915/gt/intel_gtt.h
> > > > @@ -39,6 +39,9 @@
> > > > #define NALLOC 3 /* 1 normal, 1 for concurrent threads, 1 for preallocation */
> > > > +#define I915_PAGE_PRESENT BIT_ULL(0)
> > > > +#define I915_PAGE_RW BIT_ULL(1)
> > > > +
> > > > #define I915_GTT_PAGE_SIZE_4K BIT_ULL(12)
> > > > #define I915_GTT_PAGE_SIZE_64K BIT_ULL(16)
> > > > #define I915_GTT_PAGE_SIZE_2M BIT_ULL(21)
> > > > diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
> > > > index 53d0cb327539..8f6a055854f7 100644
> > > > --- a/drivers/gpu/drm/i915/gvt/gtt.c
> > > > +++ b/drivers/gpu/drm/i915/gvt/gtt.c
> > > > @@ -446,17 +446,17 @@ static bool gen8_gtt_test_present(struct intel_gvt_gtt_entry *e)
> > > > || e->type == GTT_TYPE_PPGTT_ROOT_L4_ENTRY)
> > > > return (e->val64 != 0);
> > > > else
> > > > - return (e->val64 & _PAGE_PRESENT);
> > > > + return (e->val64 & I915_PAGE_PRESENT);
> > > > }
> > > > static void gtt_entry_clear_present(struct intel_gvt_gtt_entry *e)
> > > > {
> > > > - e->val64 &= ~_PAGE_PRESENT;
> > > > + e->val64 &= ~I915_PAGE_PRESENT;
> > > > }
> > > > static void gtt_entry_set_present(struct intel_gvt_gtt_entry *e)
> > > > {
> > > > - e->val64 |= _PAGE_PRESENT;
> > > > + e->val64 |= I915_PAGE_PRESENT;
> > > > }
> > > > static bool gen8_gtt_test_64k_splited(struct intel_gvt_gtt_entry *e)
> > > > @@ -2439,7 +2439,7 @@ static int alloc_scratch_pages(struct intel_vgpu *vgpu,
> > > > /* The entry parameters like present/writeable/cache type
> > > > * set to the same as i915's scratch page tree.
> > > > */
> > > > - se.val64 |= _PAGE_PRESENT | _PAGE_RW;
> > > > + se.val64 |= I915_PAGE_PRESENT | I915_PAGE_RW;
> > > > if (type == GTT_TYPE_PPGTT_PDE_PT)
> > > > se.val64 |= PPAT_CACHED;
> > > > @@ -2896,7 +2896,7 @@ void intel_gvt_restore_ggtt(struct intel_gvt *gvt)
> > > > offset = vgpu_aperture_gmadr_base(vgpu) >> PAGE_SHIFT;
> > > > for (idx = 0; idx < num_low; idx++) {
> > > > pte = mm->ggtt_mm.host_ggtt_aperture[idx];
> > > > - if (pte & _PAGE_PRESENT)
> > > > + if (pte & I915_PAGE_PRESENT)
> > > > write_pte64(vgpu->gvt->gt->ggtt, offset + idx, pte);
> > > > }
> > > > @@ -2904,7 +2904,7 @@ void intel_gvt_restore_ggtt(struct intel_gvt *gvt)
> > > > offset = vgpu_hidden_gmadr_base(vgpu) >> PAGE_SHIFT;
> > > > for (idx = 0; idx < num_hi; idx++) {
> > > > pte = mm->ggtt_mm.host_ggtt_hidden[idx];
> > > > - if (pte & _PAGE_PRESENT)
> > > > + if (pte & I915_PAGE_PRESENT)
> > > > write_pte64(vgpu->gvt->gt->ggtt, offset + idx, pte);
> > > > }
> > > > }
> > > > --
> > > > 2.25.1
> > > >
> > > --
> > > Matt Roper
> > > Graphics Software Engineer
> > > VTT-OSGC Platform Enablement
> > > Intel Corporation
> > > (916) 356-2795
--
Matt Roper
Graphics Software Engineer
VTT-OSGC Platform Enablement
Intel Corporation
(916) 356-2795
