Re: [Intel-gfx] [PATCH] drm/i915: Add lmem fault handler

From: Chris Wilson <chris@chris-wilson.co.uk>
To: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>,
	Matthew Auld <matthew.william.auld@gmail.com>
Cc: Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
	Matthew Auld <matthew.auld@intel.com>
Subject: Re: [Intel-gfx] [PATCH] drm/i915: Add lmem fault handler
Date: Thu, 05 Dec 2019 10:31:47 +0000	[thread overview]
Message-ID: <157554190714.22727.11425566328816516124@skylake-alporthouse-com> (raw)
In-Reply-To: <CAM0jSHMgzJBsYfKvKSYrqnBqSUaFqG45eL83_kc8y_w3YdR8hg@mail.gmail.com>

Quoting Matthew Auld (2019-12-05 10:20:55)
> On Thu, 5 Dec 2019 at 10:14, Abdiel Janulgue
> <abdiel.janulgue@linux.intel.com> wrote:
> >
> > Fault handler to handle missing pages for lmem objects.
> >
> > Signed-off-by: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
> > Signed-off-by: Matthew Auld <matthew.auld@intel.com>
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/gem/i915_gem_lmem.c | 43 ++++++++++++++++++++++++
> >  drivers/gpu/drm/i915/gem/i915_gem_lmem.h |  6 ++++
> >  drivers/gpu/drm/i915/gem/i915_gem_mman.c | 15 +++++++--
> >  drivers/gpu/drm/i915/gem/i915_gem_mman.h |  1 +
> >  4 files changed, 63 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_lmem.c b/drivers/gpu/drm/i915/gem/i915_gem_lmem.c
> > index 0e2bf6b7e143..78ac8d160cd7 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_lmem.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_lmem.c
> > @@ -6,8 +6,40 @@
> >  #include "intel_memory_region.h"
> >  #include "gem/i915_gem_region.h"
> >  #include "gem/i915_gem_lmem.h"
> > +#include "gem/i915_gem_mman.h"
> >  #include "i915_drv.h"
> >
> > +vm_fault_t vm_fault_lmem(struct vm_fault *vmf)
> > +{
> > +       struct vm_area_struct *area = vmf->vma;
> > +       struct i915_mmap_offset *priv = area->vm_private_data;
> > +       struct drm_i915_gem_object *obj = priv->obj;
> > +       unsigned long size = area->vm_end - area->vm_start;
> > +       bool write = area->vm_flags & VM_WRITE;
> > +       vm_fault_t vmf_ret;
> > +       int i, ret;
> > +
> > +       /* Sanity check that we allow writing into this object */
> > +       if (i915_gem_object_is_readonly(obj) && write)
> > +               return VM_FAULT_SIGBUS;
> > +
> > +       ret = i915_gem_object_pin_pages(obj);
> > +       if (ret)
> > +               return i915_error_to_vmf_fault(ret);
> 
> Don't we need to handle -ENXIO in i915_error_to_vmf_fault?
> 
> > +
> > +       for (i = 0; i < size >> PAGE_SHIFT; i++) {
> > +               vmf_ret = vmf_insert_pfn(area,
> > +                                        (unsigned long)area->vm_start + i * PAGE_SIZE,
> > +                                        i915_gem_object_lmem_io_pfn(obj, i));
> > +               if (vmf_ret != VM_FAULT_NOPAGE)
> > +                       break;
> > +       }
> > +
> > +       i915_gem_object_unpin_pages(obj);
> > +
> > +       return vmf_ret;
> > +}
> > +
> >  const struct drm_i915_gem_object_ops i915_gem_lmem_obj_ops = {
> >         .flags = I915_GEM_OBJECT_HAS_IOMEM,
> >
> > @@ -56,6 +88,17 @@ i915_gem_object_lmem_io_map(struct drm_i915_gem_object *obj,
> >         return io_mapping_map_wc(&obj->mm.region->iomap, offset, size);
> >  }
> >
> > +unsigned long i915_gem_object_lmem_io_pfn(struct drm_i915_gem_object *obj,
> > +                                         unsigned long n)
> > +{
> > +       struct intel_memory_region *mem = obj->mm.region;
> > +       resource_size_t offset;
> > +
> > +       offset = i915_gem_object_get_dma_address(obj, n);
> 
> offset -= mem->region.start; for poor old fake local-memory.

And so one asks for the selftests...
-Chris
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