Re: [PATCH 3/6] drm/amdgpu: Flush VM updates for split bindings eagerly.

[Lang Yu <Lang.Yu@amd.com>]

On 10/31/ , Christian König wrote:
> Am 31.10.23 um 14:59 schrieb Bas Nieuwenhuizen:
> > 
> > 
> > On Tue, Oct 31, 2023 at 2:57 PM Christian König
> > <christian.koenig@amd.com> wrote:
> > 
> >     Am 31.10.23 um 14:40 schrieb Tatsuyuki Ishi:
> >     > The current amdgpu_gem_va_update_vm only tries to perform
> >     updates for the
> >     > BO specified in the GEM ioctl; however, when a binding is split, the
> >     > adjacent bindings also need to be updated. Such updates
> >     currently ends up
> >     > getting deferred until next submission which causes stalls.
> > 
> >     Yeah, that is a necessity. The hardware simply doesn't support
> >     what you
> >     try to do here in all cases.
> > 
> > 
> > What can the hardware not do here? Is this just needing to wait for TLB
> > flushes before we can free pagetables, can we just delay that?
> 
> On some hardware generations (especially Navi1x, but also everything older
> than Polaris) you can't invalidate the TLB while it is in use.

Hi Christian,

non-legacy invalidation can invalidate the TLB while it is in use.
Right? Thanks.

Regards,
Lang

> For Polaris and older it just means that you don't have a guarantee that the
> shader can't access the memory any more. So delaying the free operation
> helps here.
> 
> But for Navi1x it's a workaround for a hardware bug. If you try to
> invalidate the TLB while it is in use you can potentially triggering memory
> accesses to random addresses.
> 
> That's why we still delay TLB invalidation's to the next CS and use a new
> VMID for each submission instead of invalidating the old one.
> 
> I'm currently working on changing that for Navi2x and newer (maybe Vega as
> well), but this is something you can really only do on some hw generations
> after validating that it works.
> 
> Regards,
> Christian.
> 
> > 
> > 
> >     So this approach won't work in general.
> > 
> >     Regards,
> >     Christian.
> > 
> >     >
> >     > Introduce a new state "dirty", shared between per-VM BOs and
> >     traditional
> >     > BOs, containing all BOs that have pending updates in `invalids`.
> >     > amdgpu_gem_va_update_vm will now simply flush any pending
> >     updates for BOs
> >     > in the dirty state.
> >     >
> >     > Signed-off-by: Tatsuyuki Ishi <ishitatsuyuki@gmail.com>
> >     > ---
> >     >   drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 18 ++++---
> >     >   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c  | 66
> >     ++++++++++++++++++-------
> >     >   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h  |  3 ++
> >     >   3 files changed, 63 insertions(+), 24 deletions(-)
> >     >
> >     > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> >     b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> >     > index a1b15d0d6c48..01d3a97248b0 100644
> >     > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> >     > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> >     > @@ -604,10 +604,9 @@ int amdgpu_gem_metadata_ioctl(struct
> >     drm_device *dev, void *data,
> >     >    * vital here, so they are not reported back to userspace.
> >     >    */
> >     >   static void amdgpu_gem_va_update_vm(struct amdgpu_device *adev,
> >     > -                                 struct amdgpu_vm *vm,
> >     > -                                 struct amdgpu_bo_va *bo_va,
> >     > -                                 uint32_t operation)
> >     > +                                 struct amdgpu_vm *vm)
> >     >   {
> >     > +     struct amdgpu_bo_va *bo_va;
> >     >       int r;
> >     >
> >     >       if (!amdgpu_vm_ready(vm))
> >     > @@ -617,12 +616,18 @@ static void amdgpu_gem_va_update_vm(struct
> >     amdgpu_device *adev,
> >     >       if (r)
> >     >               goto error;
> >     >
> >     > -     if (operation == AMDGPU_VA_OP_MAP ||
> >     > -         operation == AMDGPU_VA_OP_REPLACE) {
> >     > +     spin_lock(&vm->status_lock);
> >     > +     while (!list_empty(&vm->dirty)) {
> >     > +             bo_va = list_first_entry(&vm->dirty, struct
> >     amdgpu_bo_va,
> >     > +                                      base.vm_status);
> >     > +             spin_unlock(&vm->status_lock);
> >     > +
> >     >               r = amdgpu_vm_bo_update(adev, bo_va, false);
> >     >               if (r)
> >     >                       goto error;
> >     > +             spin_lock(&vm->status_lock);
> >     >       }
> >     > +     spin_unlock(&vm->status_lock);
> >     >
> >     >       r = amdgpu_vm_update_pdes(adev, vm, false);
> >     >
> >     > @@ -792,8 +797,7 @@ int amdgpu_gem_va_ioctl(struct drm_device
> >     *dev, void *data,
> >     >               break;
> >     >       }
> >     >       if (!r && !(args->flags & AMDGPU_VM_DELAY_UPDATE) &&
> >     !amdgpu_vm_debug)
> >     > -             amdgpu_gem_va_update_vm(adev, &fpriv->vm, bo_va,
> >     > -  args->operation);
> >     > +             amdgpu_gem_va_update_vm(adev, &fpriv->vm);
> >     >
> >     >   error:
> >     >       drm_exec_fini(&exec);
> >     > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> >     b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> >     > index dd6f72e2a1d6..01d31891cd05 100644
> >     > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> >     > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> >     > @@ -191,6 +191,21 @@ static void amdgpu_vm_bo_set_evicted(struct
> >     amdgpu_vm_bo_base *vm_bo, bool evict
> >     >       spin_unlock(&vm_bo->vm->status_lock);
> >     >   }
> >     >
> >     > +/**
> >     > + * amdgpu_vm_bo_dirty - vm_bo is dirty
> >     > + *
> >     > + * @vm_bo: vm_bo which is dirty
> >     > + *
> >     > + * State for normal and per VM BOs that are not moved, but have
> >     new entries in
> >     > + * bo_va->invalids.
> >     > + */
> >     > +static void amdgpu_vm_bo_dirty(struct amdgpu_vm_bo_base *vm_bo)
> >     > +{
> >     > +     spin_lock(&vm_bo->vm->status_lock);
> >     > +     list_move(&vm_bo->vm_status, &vm_bo->vm->dirty);
> >     > +     spin_unlock(&vm_bo->vm->status_lock);
> >     > +}
> >     > +
> >     >   /**
> >     >    * amdgpu_vm_bo_moved - vm_bo is moved
> >     >    *
> >     > @@ -1042,6 +1057,9 @@ void amdgpu_vm_get_memory(struct amdgpu_vm
> >     *vm,
> >     >       list_for_each_entry_safe(bo_va, tmp, &vm->evicted,
> >     base.eviction_status)
> >     >               amdgpu_vm_bo_get_memory(bo_va, stats);
> >     >
> >     > +     list_for_each_entry_safe(bo_va, tmp, &vm->dirty,
> >     base.vm_status)
> >     > +             amdgpu_vm_bo_get_memory(bo_va, stats);
> >     > +
> >     >       list_for_each_entry_safe(bo_va, tmp, &vm->relocated,
> >     base.vm_status)
> >     >               amdgpu_vm_bo_get_memory(bo_va, stats);
> >     >
> >     > @@ -1411,6 +1429,17 @@ int amdgpu_vm_handle_moved(struct
> >     amdgpu_device *adev,
> >     >                       dma_resv_unlock(resv);
> >     >               spin_lock(&vm->status_lock);
> >     >       }
> >     > +
> >     > +     while (!list_empty(&vm->dirty)) {
> >     > +             bo_va = list_first_entry(&vm->dirty, struct
> >     amdgpu_bo_va,
> >     > +                                      base.vm_status);
> >     > +             spin_unlock(&vm->status_lock);
> >     > +
> >     > +             r = amdgpu_vm_bo_update(adev, bo_va, false);
> >     > +             if (r)
> >     > +                     return r;
> >     > +             spin_lock(&vm->status_lock);
> >     > +     }
> >     >       spin_unlock(&vm->status_lock);
> >     >
> >     >       return 0;
> >     > @@ -1476,19 +1505,16 @@ static void
> >     amdgpu_vm_bo_insert_map(struct amdgpu_device *adev,
> >     >                                   struct amdgpu_bo_va_mapping
> >     *mapping)
> >     >   {
> >     >       struct amdgpu_vm *vm = bo_va->base.vm;
> >     > -     struct amdgpu_bo *bo = bo_va->base.bo <http://base.bo>;
> >     >
> >     >       mapping->bo_va = bo_va;
> >     >       list_add(&mapping->list, &bo_va->invalids);
> >     >       amdgpu_vm_it_insert(mapping, &vm->va);
> >     > +     if (!bo_va->base.moved)
> >     > +             amdgpu_vm_bo_dirty(&bo_va->base);
> >     >
> >     >       if (mapping->flags & AMDGPU_PTE_PRT)
> >     >               amdgpu_vm_prt_get(adev);
> >     >
> >     > -     if (bo && bo->tbo.base.resv == vm->root.bo->tbo.base.resv &&
> >     > -         !bo_va->base.moved) {
> >     > -             amdgpu_vm_bo_moved(&bo_va->base);
> >     > -     }
> >     >       trace_amdgpu_vm_bo_map(bo_va, mapping);
> >     >   }
> >     >
> >     > @@ -1725,6 +1751,8 @@ int amdgpu_vm_bo_clear_mappings(struct
> >     amdgpu_device *adev,
> >     >                       before->flags = tmp->flags;
> >     >                       before->bo_va = tmp->bo_va;
> >     >                       list_add(&before->list,
> >     &tmp->bo_va->invalids);
> >     > +                     if (!tmp->bo_va->base.moved)
> >     > +  amdgpu_vm_bo_dirty(&tmp->bo_va->base);
> >     >               }
> >     >
> >     >               /* Remember mapping split at the end */
> >     > @@ -1736,6 +1764,8 @@ int amdgpu_vm_bo_clear_mappings(struct
> >     amdgpu_device *adev,
> >     >                       after->flags = tmp->flags;
> >     >                       after->bo_va = tmp->bo_va;
> >     >                       list_add(&after->list, &tmp->bo_va->invalids);
> >     > +                     if (!tmp->bo_va->base.moved)
> >     > +  amdgpu_vm_bo_dirty(&tmp->bo_va->base);
> >     >               }
> >     >
> >     >               list_del(&tmp->list);
> >     > @@ -1761,30 +1791,18 @@ int amdgpu_vm_bo_clear_mappings(struct
> >     amdgpu_device *adev,
> >     >
> >     >       /* Insert partial mapping before the range */
> >     >       if (!list_empty(&before->list)) {
> >     > -             struct amdgpu_bo *bo = before->bo_va->base.bo
> >     <http://base.bo>;
> >     > -
> >     >               amdgpu_vm_it_insert(before, &vm->va);
> >     >               if (before->flags & AMDGPU_PTE_PRT)
> >     >                       amdgpu_vm_prt_get(adev);
> >     > -
> >     > -             if (bo && bo->tbo.base.resv ==
> >     vm->root.bo->tbo.base.resv &&
> >     > -                 !before->bo_va->base.moved)
> >     > -  amdgpu_vm_bo_moved(&before->bo_va->base);
> >     >       } else {
> >     >               kfree(before);
> >     >       }
> >     >
> >     >       /* Insert partial mapping after the range */
> >     >       if (!list_empty(&after->list)) {
> >     > -             struct amdgpu_bo *bo = after->bo_va->base.bo
> >     <http://base.bo>;
> >     > -
> >     >               amdgpu_vm_it_insert(after, &vm->va);
> >     >               if (after->flags & AMDGPU_PTE_PRT)
> >     >                       amdgpu_vm_prt_get(adev);
> >     > -
> >     > -             if (bo && bo->tbo.base.resv ==
> >     vm->root.bo->tbo.base.resv &&
> >     > -                 !after->bo_va->base.moved)
> >     > -  amdgpu_vm_bo_moved(&after->bo_va->base);
> >     >       } else {
> >     >               kfree(after);
> >     >       }
> >     > @@ -2136,6 +2154,7 @@ int amdgpu_vm_init(struct amdgpu_device
> >     *adev, struct amdgpu_vm *vm, int32_t xcp
> >     >       INIT_LIST_HEAD(&vm->evicted);
> >     >       INIT_LIST_HEAD(&vm->relocated);
> >     >       INIT_LIST_HEAD(&vm->moved);
> >     > +     INIT_LIST_HEAD(&vm->dirty);
> >     >       INIT_LIST_HEAD(&vm->idle);
> >     >       INIT_LIST_HEAD(&vm->invalidated);
> >     >       spin_lock_init(&vm->status_lock);
> >     > @@ -2648,11 +2667,13 @@ void amdgpu_debugfs_vm_bo_info(struct
> >     amdgpu_vm *vm, struct seq_file *m)
> >     >   {
> >     >       struct amdgpu_bo_va *bo_va, *tmp;
> >     >       u64 total_idle = 0;
> >     > +     u64 total_dirty = 0;
> >     >       u64 total_relocated = 0;
> >     >       u64 total_moved = 0;
> >     >       u64 total_invalidated = 0;
> >     >       u64 total_done = 0;
> >     >       unsigned int total_idle_objs = 0;
> >     > +     unsigned int total_dirty_objs = 0;
> >     >       unsigned int total_relocated_objs = 0;
> >     >       unsigned int total_moved_objs = 0;
> >     >       unsigned int total_invalidated_objs = 0;
> >     > @@ -2669,6 +2690,15 @@ void amdgpu_debugfs_vm_bo_info(struct
> >     amdgpu_vm *vm, struct seq_file *m)
> >     >       total_idle_objs = id;
> >     >       id = 0;
> >     >
> >     > +     seq_puts(m, "\tDirty BOs:\n");
> >     > +     list_for_each_entry_safe(bo_va, tmp, &vm->dirty,
> >     base.vm_status) {
> >     > +             if (!bo_va->base.bo <http://base.bo>)
> >     > +                     continue;
> >     > +             total_dirty += amdgpu_bo_print_info(id++,
> >     bo_va->base.bo <http://base.bo>, m);
> >     > +     }
> >     > +     total_dirty_objs = id;
> >     > +     id = 0;
> >     > +
> >     >       seq_puts(m, "\tRelocated BOs:\n");
> >     >       list_for_each_entry_safe(bo_va, tmp, &vm->relocated,
> >     base.vm_status) {
> >     >               if (!bo_va->base.bo <http://base.bo>)
> >     > @@ -2707,6 +2737,8 @@ void amdgpu_debugfs_vm_bo_info(struct
> >     amdgpu_vm *vm, struct seq_file *m)
> >     >
> >     >       seq_printf(m, "\tTotal idle size: %12lld\tobjs:\t%d\n",
> >     total_idle,
> >     >                  total_idle_objs);
> >     > +     seq_printf(m, "\tTotal dirty size:  %12lld\tobjs:\t%d\n",
> >     total_dirty,
> >     > +                total_dirty_objs);
> >     >       seq_printf(m, "\tTotal relocated size:
> >      %12lld\tobjs:\t%d\n", total_relocated,
> >     >                  total_relocated_objs);
> >     >       seq_printf(m, "\tTotal moved size:  %12lld\tobjs:\t%d\n",
> >     total_moved,
> >     > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> >     b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> >     > index d9ab97eabda9..f91d4fcf80b8 100644
> >     > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> >     > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> >     > @@ -276,6 +276,9 @@ struct amdgpu_vm {
> >     >       /* per VM BOs moved, but not yet updated in the PT */
> >     >       struct list_head        moved;
> >     >
> >     > +     /* normal and per VM BOs that are not moved, but have new
> >     PT entries */
> >     > +     struct list_head        dirty;
> >     > +
> >     >       /* All BOs of this VM not currently in the state machine */
> >     >       struct list_head        idle;
> >     >
> >