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

[Abdiel Janulgue <abdiel.janulgue@linux.intel.com>]

On 12/12/2019 17.19, Chris Wilson wrote:
> Quoting Matthew Auld (2019-12-12 15:11:02)
>> On Thu, 12 Dec 2019 at 14:20, Chris Wilson <chris@chris-wilson.co.uk> wrote:
>>>
>>> Quoting Abdiel Janulgue (2019-12-12 11:34:38)
>>>> Fault handler to handle missing pages for lmem objects.
>>>>
>>>> v3: Add get_vm_cpu_ops, iterate over all memory regions in the
>>>>     lmem selftest, use remap_io_mapping.
>>>>
>>>> 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      |  40 +++++
>>>>  drivers/gpu/drm/i915/gem/i915_gem_lmem.h      |   6 +
>>>>  drivers/gpu/drm/i915/gem/i915_gem_mman.c      |  32 +++-
>>>>  drivers/gpu/drm/i915/gem/i915_gem_mman.h      |   1 +
>>>>  .../drm/i915/gem/selftests/i915_gem_mman.c    | 137 +++++++++++++++---
>>>>  5 files changed, 188 insertions(+), 28 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..bbe625935005 100644
>>>> --- a/drivers/gpu/drm/i915/gem/i915_gem_lmem.c
>>>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_lmem.c
>>>> @@ -6,8 +6,36 @@
>>>>  #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_iomem(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;
>>>> +       struct intel_memory_region *mem = obj->mm.region;
>>>> +       unsigned long size = area->vm_end - area->vm_start;
>>>> +       bool write = area->vm_flags & VM_WRITE;
>>>> +       int 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);
>>>> +
>>>> +       ret = remap_io_mapping(area, area->vm_start,
>>>> +                              i915_gem_object_lmem_io_pfn(obj, 0), size,
>>>> +                              &mem->iomap);
>>>
>>> So this implementation only works with contiguous objects, right?
>>
>> Hmm can't we go back to what we had before, so support !contiguous also?
> 
> The fun part is that you can do both :) Do a discontiguous
> remap_io_mapping() The queue part is that remap_io_mapping() avoids the
> O(N^2), and should give us O(N) instead.

So just to be clear,

if (obj->flags & I915_BO_ALLOC_CONTIGUOUS) {
	remap_io_mapping(...)
} else {
	for(...)
		vmf_insert_pfn()
}

??

- Abdiel
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