On Thu, Jul 22, 2021 at 3:44 AM Matthew Auld
<matthew.william.auld@xxxxxxxxx> wrote:
>
> On Wed, 21 Jul 2021 at 21:28, Jason Ekstrand <jason@xxxxxxxxxxxxxx> wrote:
> >
> > On Thu, Jul 15, 2021 at 5:16 AM Matthew Auld <matthew.auld@xxxxxxxxx> wrote:
> > >
> > > From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > >
> > > Jason Ekstrand requested a more efficient method than userptr+set-domain
> > > to determine if the userptr object was backed by a complete set of pages
> > > upon creation. To be more efficient than simply populating the userptr
> > > using get_user_pages() (as done by the call to set-domain or execbuf),
> > > we can walk the tree of vm_area_struct and check for gaps or vma not
> > > backed by struct page (VM_PFNMAP). The question is how to handle
> > > VM_MIXEDMAP which may be either struct page or pfn backed...
> > >
> > > With discrete are going to drop support for set_domain(), so offering a
> > > way to probe the pages, without having to resort to dummy batches has
> > > been requested.
> > >
> > > v2:
> > > - add new query param for the PROPBE flag, so userspace can easily
> > > check if the kernel supports it(Jason).
> > > - use mmap_read_{lock, unlock}.
> > > - add some kernel-doc.
> > >
> > > Testcase: igt/gem_userptr_blits/probe
> > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > > Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
> > > Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> > > Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> > > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
> > > Cc: Jordan Justen <jordan.l.justen@xxxxxxxxx>
> > > Cc: Kenneth Graunke <kenneth@xxxxxxxxxxxxx>
> > > Cc: Jason Ekstrand <jason@xxxxxxxxxxxxxx>
> > > Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> > > Cc: Ramalingam C <ramalingam.c@xxxxxxxxx>
> > > ---
> > > drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 40 ++++++++++++++++++++-
> > > drivers/gpu/drm/i915/i915_getparam.c | 3 ++
> > > include/uapi/drm/i915_drm.h | 18 ++++++++++
> > > 3 files changed, 60 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> > > index 56edfeff8c02..fd6880328596 100644
> > > --- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> > > +++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> > > @@ -422,6 +422,33 @@ static const struct drm_i915_gem_object_ops i915_gem_userptr_ops = {
> > >
> > > #endif
> > >
> > > +static int
> > > +probe_range(struct mm_struct *mm, unsigned long addr, unsigned long len)
> > > +{
> > > + const unsigned long end = addr + len;
> > > + struct vm_area_struct *vma;
> > > + int ret = -EFAULT;
> > > +
> > > + mmap_read_lock(mm);
> > > + for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) {
> > > + if (vma->vm_start > addr)
> >
> > Why isn't this > end? Are we somehow guaranteed that one vma covers
> > the entire range?
>
> AFAIK we are just making sure we don't have a hole(note that we also
> update addr below), for example the user might have done a partial
> munmap. There could be multiple vma's if the kernel was unable to
> merge them. If we reach the vm_end >= end, then we know we have a
> "valid" range.
Ok. That wasn't obvious to me but I see the addr update now. Makes
sense. Might be worth a one-line comment for the next guy. Either
way,
Reviewed-by: Jason Ekstrand <jason@xxxxxxxxxxxxxx>
Thanks for wiring this up!
--Jason
> >
> > > + break;
> > > +
> > > + if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
> > > + break;
> > > +
> > > + if (vma->vm_end >= end) {
> > > + ret = 0;
> > > + break;
> > > + }
> > > +
> > > + addr = vma->vm_end;
> > > + }
> > > + mmap_read_unlock(mm);
> > > +
> > > + return ret;
> > > +}
> > > +
> > > /*
> > > * Creates a new mm object that wraps some normal memory from the process
> > > * context - user memory.
> > > @@ -477,7 +504,8 @@ i915_gem_userptr_ioctl(struct drm_device *dev,
> > > }
> > >
> > > if (args->flags & ~(I915_USERPTR_READ_ONLY |
> > > - I915_USERPTR_UNSYNCHRONIZED))
> > > + I915_USERPTR_UNSYNCHRONIZED |
> > > + I915_USERPTR_PROBE))
> > > return -EINVAL;
> > >
> > > if (i915_gem_object_size_2big(args->user_size))
> > > @@ -504,6 +532,16 @@ i915_gem_userptr_ioctl(struct drm_device *dev,
> > > return -ENODEV;
> > > }
> > >
> > > + if (args->flags & I915_USERPTR_PROBE) {
> > > + /*
> > > + * Check that the range pointed to represents real struct
> > > + * pages and not iomappings (at this moment in time!)
> > > + */
> > > + ret = probe_range(current->mm, args->user_ptr, args->user_size);
> > > + if (ret)
> > > + return ret;
> > > + }
> > > +
> > > #ifdef CONFIG_MMU_NOTIFIER
> > > obj = i915_gem_object_alloc();
> > > if (obj == NULL)
> > > diff --git a/drivers/gpu/drm/i915/i915_getparam.c b/drivers/gpu/drm/i915/i915_getparam.c
> > > index 24e18219eb50..d6d2e1a10d14 100644
> > > --- a/drivers/gpu/drm/i915/i915_getparam.c
> > > +++ b/drivers/gpu/drm/i915/i915_getparam.c
> > > @@ -163,6 +163,9 @@ int i915_getparam_ioctl(struct drm_device *dev, void *data,
> > > case I915_PARAM_PERF_REVISION:
> > > value = i915_perf_ioctl_version();
> > > break;
> > > + case I915_PARAM_HAS_USERPTR_PROBE:
> > > + value = true;
> > > + break;
> > > default:
> > > DRM_DEBUG("Unknown parameter %d\n", param->param);
> > > return -EINVAL;
> > > diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> > > index e20eeeca7a1c..2e4112bf4d38 100644
> > > --- a/include/uapi/drm/i915_drm.h
> > > +++ b/include/uapi/drm/i915_drm.h
> > > @@ -674,6 +674,9 @@ typedef struct drm_i915_irq_wait {
> > > */
> > > #define I915_PARAM_HAS_EXEC_TIMELINE_FENCES 55
> > >
> > > +/* Query if the kernel supports the I915_USERPTR_PROBE flag. */
> > > +#define I915_PARAM_HAS_USERPTR_PROBE 56
> > > +
> > > /* Must be kept compact -- no holes and well documented */
> > >
> > > typedef struct drm_i915_getparam {
> > > @@ -2178,12 +2181,27 @@ struct drm_i915_gem_userptr {
> > > * through the GTT. If the HW can't support readonly access, an error is
> > > * returned.
> > > *
> > > + * I915_USERPTR_PROBE:
> > > + *
> > > + * Probe the provided @user_ptr range and validate that the @user_ptr is
> > > + * indeed pointing to normal memory and that the range is also valid.
> > > + * For example if some garbage address is given to the kernel, then this
> > > + * should complain.
> > > + *
> > > + * Returns -EFAULT if the probe failed.
> > > + *
> > > + * Note that this doesn't populate the backing pages.
> > > + *
> > > + * The kernel supports this feature if I915_PARAM_HAS_USERPTR_PROBE
> > > + * returns a non-zero value.
> > > + *
> > > * I915_USERPTR_UNSYNCHRONIZED:
> > > *
> > > * NOT USED. Setting this flag will result in an error.
> > > */
> > > __u32 flags;
> > > #define I915_USERPTR_READ_ONLY 0x1
> > > +#define I915_USERPTR_PROBE 0x2
> > > #define I915_USERPTR_UNSYNCHRONIZED 0x80000000
> > > /**
> > > * @handle: Returned handle for the object.
> > > --
> > > 2.26.3
> > >
> > _______________________________________________
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> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
