[Intel-xe] [RFC PATCH] drm/xe/dgfx: Release mmap mappings on rpm suspend
Gupta, Anshuman
anshuman.gupta at intel.com
Thu Aug 31 05:23:40 UTC 2023
> -----Original Message-----
> From: Vivi, Rodrigo <rodrigo.vivi at intel.com>
> Sent: Thursday, August 31, 2023 2:35 AM
> To: Nilawar, Badal <badal.nilawar at intel.com>
> Cc: Gupta, Anshuman <anshuman.gupta at intel.com>; intel-
> xe at lists.freedesktop.org; Auld, Matthew <matthew.auld at intel.com>
> Subject: Re: [Intel-xe] [RFC PATCH] drm/xe/dgfx: Release mmap mappings
> on rpm suspend
>
> On Mon, Aug 28, 2023 at 10:00:31PM +0530, Nilawar, Badal wrote:
> >
> >
> > On 28-08-2023 17:46, Gupta, Anshuman wrote:
> > >
> > >
> > > > -----Original Message-----
> > > > From: Nilawar, Badal <badal.nilawar at intel.com>
> > > > Sent: Thursday, August 24, 2023 11:16 PM
> > > > To: intel-xe at lists.freedesktop.org
> > > > Cc: Gupta, Anshuman <anshuman.gupta at intel.com>; Auld, Matthew
> > > > <matthew.auld at intel.com>; Vivi, Rodrigo <rodrigo.vivi at intel.com>
> > > > Subject: [RFC PATCH] drm/xe/dgfx: Release mmap mappings on rpm
> > > > suspend
> > > >
> > > > Release all mmap mappings for all vram objects which are
> > > > associated with userfault such that, while pcie function in D3hot,
> > > > any access to memory mappings will raise a userfault.
> > > >
> > > > Upon userfault, in order to access memory mappings, if graphics
> > > > function is in
> > > > D3 then runtime resume of dgpu will be triggered to transition to D0.
> > > IMO we need a configurable threshold to control the behavior of mmap
> > > mappings Invalidation, if vram usages is crosses to certain
> > > threshold, disable the runtime PM for entire life time of mapping.
> > Agreed. Other option could be disable rpm on server descrete graphics
> > for entire life time of mapping. But mainitaning threshold is more
> > promising and gives control to user.
>
> what use cases we have here for this?
> I believe that for discrete we could entirely block rpm if we have display or if
> we have shared dma_buf. any other case we should handle?
If Discrete is used for display then anyhow display is going to block runtime PM completely(be it PSR or Non-PSR).
The use case is with display turned off or with hybrid gpu use case.
Currently on Xe we are missing to have mem access ref count on mmap mapping and therefore mmap for vram bo is broken.
dma-buf will be also the use case in hybrid gpu use case.
Thanks,
Anshuman Gupta.
>
> >
> > Regards,
> > Badal
> > > Thanks,
> > > Anshuman Gupta
> > > >
> > > > Cc: Matthew Auld <matthew.auld at intel.com>
> > > > Cc: Anshuman Gupta <anshuman.gupta at intel.com>
> > > > Signed-off-by: Badal Nilawar <badal.nilawar at intel.com>
> > > > ---
> > > > drivers/gpu/drm/xe/xe_bo.c | 53
> ++++++++++++++++++++++++++--
> > > > drivers/gpu/drm/xe/xe_bo.h | 2 ++
> > > > drivers/gpu/drm/xe/xe_bo_types.h | 6 ++++
> > > > drivers/gpu/drm/xe/xe_device_types.h | 20 +++++++++++
> > > > drivers/gpu/drm/xe/xe_pm.c | 7 ++++
> > > > 5 files changed, 85 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/xe/xe_bo.c
> > > > b/drivers/gpu/drm/xe/xe_bo.c index 1ab682d61e3c..4192bfcd8013
> > > > 100644
> > > > --- a/drivers/gpu/drm/xe/xe_bo.c
> > > > +++ b/drivers/gpu/drm/xe/xe_bo.c
> > > > @@ -776,6 +776,18 @@ static int xe_bo_move(struct
> > > > ttm_buffer_object *ttm_bo, bool evict,
> > > > dma_fence_put(fence);
> > > > }
> > > >
> > > > + /*
> > > > + * TTM has already nuked the mmap for us (see
> > > > ttm_bo_unmap_virtual),
> > > > + * so if we moved from VRAM make sure to unlink this from the
> > > > userfault
> > > > + * tracking.
> > > > + */
> > > > + if (mem_type_is_vram(old_mem_type)) {
> > > > + spin_lock(&xe->mem_access.vram_userfault_lock);
> > > > + if (!list_empty(&bo->vram_userfault_link))
> > > > + list_del_init(&bo->vram_userfault_link);
> > > > + spin_unlock(&xe->mem_access.vram_userfault_lock);
> > > > + }
> > > > +
> > > > xe_device_mem_access_put(xe);
> > > > trace_printk("new_mem->mem_type=%d\n", new_mem-
> > > > > mem_type);
> > > >
> > > > @@ -1100,6 +1112,8 @@ static vm_fault_t xe_gem_fault(struct
> > > > vm_fault
> > > > *vmf) {
> > > > struct ttm_buffer_object *tbo = vmf->vma->vm_private_data;
> > > > struct drm_device *ddev = tbo->base.dev;
> > > > + struct xe_bo *bo = ttm_to_xe_bo(tbo);
> > > > + struct xe_device *xe = to_xe_device(ddev);
> > > > vm_fault_t ret;
> > > > int idx, r = 0;
> > > >
> > > > @@ -1107,9 +1121,10 @@ static vm_fault_t xe_gem_fault(struct
> > > > vm_fault
> > > > *vmf)
> > > > if (ret)
> > > > return ret;
> > > >
> > > > - if (drm_dev_enter(ddev, &idx)) {
> > > > - struct xe_bo *bo = ttm_to_xe_bo(tbo);
> > > > + if (tbo->resource->bus.is_iomem)
> > > > + xe_device_mem_access_get(xe);
> > > >
> > > > + if (drm_dev_enter(ddev, &idx)) {
> > > > trace_xe_bo_cpu_fault(bo);
> > > >
> > > > if (should_migrate_to_system(bo)) { @@ -1127,10 +1142,25
> @@
> > > > static vm_fault_t xe_gem_fault(struct vm_fault
> > > > *vmf)
> > > > } else {
> > > > ret = ttm_bo_vm_dummy_page(vmf, vmf->vma-
> > > > > vm_page_prot);
> > > > }
> > > > +
> > > > if (ret == VM_FAULT_RETRY && !(vmf->flags &
> > > > FAULT_FLAG_RETRY_NOWAIT))
> > > > - return ret;
> > > > + goto out_rpm;
> > > > + /*
> > > > + * ttm_bo_vm_reserve() already has dma_resv_lock.
> > > > + * vram_userfault_count is protected by dma_resv lock and rpm
> > > > wakeref.
> > > > + */
> > > > + if (ret == VM_FAULT_NOPAGE &&
> > > > xe_device_mem_access_ongoing(xe) && !bo->vram_userfault_count)
> {
> > > > + bo->vram_userfault_count = 1;
> > > > + spin_lock(&xe->mem_access.vram_userfault_lock);
> > > > + list_add(&bo->vram_userfault_link, &xe-
> > > > > mem_access.vram_userfault_list);
> > > > + spin_unlock(&xe->mem_access.vram_userfault_lock);
> > > >
> > > > + XE_WARN_ON(!tbo->resource->bus.is_iomem);
> > > > + }
> > > > dma_resv_unlock(tbo->base.resv);
> > > > +out_rpm:
> > > > + if(tbo->resource->bus.is_iomem &&
> > > > xe_device_mem_access_ongoing(xe))
> > > > + xe_device_mem_access_put(xe);
> > > > return ret;
> > > > }
> > > >
> > > > @@ -2108,6 +2138,23 @@ int xe_bo_dumb_create(struct drm_file
> > > > *file_priv,
> > > > return err;
> > > > }
> > > >
> > > > +void xe_bo_runtime_pm_release_mmap_offset(struct xe_bo *bo) {
> > > > + struct ttm_buffer_object *tbo = &bo->ttm;
> > > > + struct ttm_device *bdev = tbo->bdev;
> > > > +
> > > > + drm_vma_node_unmap(&tbo->base.vma_node, bdev-
> > > > > dev_mapping);
> > > > +
> > > > + /*
> > > > + * We have exclusive access here via runtime suspend. All other
> > > > callers
> > > > + * must first grab the rpm wakeref.
> > > > + */
> > > > + XE_WARN_ON(!bo->vram_userfault_count);
> > > > + list_del(&bo->vram_userfault_link);
> > > > + bo->vram_userfault_count = 0;
> > > > +}
> > > > +
> > > > +
> > > > #if IS_ENABLED(CONFIG_DRM_XE_KUNIT_TEST)
> > > > #include "tests/xe_bo.c"
> > > > #endif
> > > > diff --git a/drivers/gpu/drm/xe/xe_bo.h
> > > > b/drivers/gpu/drm/xe/xe_bo.h index 0823dda0f31b..6b86f326c700
> > > > 100644
> > > > --- a/drivers/gpu/drm/xe/xe_bo.h
> > > > +++ b/drivers/gpu/drm/xe/xe_bo.h
> > > > @@ -247,6 +247,8 @@ int xe_gem_create_ioctl(struct drm_device
> > > > *dev, void *data,
> > > > struct drm_file *file);
> > > > int xe_gem_mmap_offset_ioctl(struct drm_device *dev, void *data,
> > > > struct drm_file *file);
> > > > +void xe_bo_runtime_pm_release_mmap_offset(struct xe_bo *bo);
> > > > +
> > > > int xe_bo_dumb_create(struct drm_file *file_priv,
> > > > struct drm_device *dev,
> > > > struct drm_mode_create_dumb *args); diff --git
> > > > a/drivers/gpu/drm/xe/xe_bo_types.h
> > > > b/drivers/gpu/drm/xe/xe_bo_types.h
> > > > index f6ee920303af..cdca91a378c4 100644
> > > > --- a/drivers/gpu/drm/xe/xe_bo_types.h
> > > > +++ b/drivers/gpu/drm/xe/xe_bo_types.h
> > > > @@ -68,6 +68,12 @@ struct xe_bo {
> > > > struct llist_node freed;
> > > > /** @created: Whether the bo has passed initial creation */
> > > > bool created;
> > > > + /**
> > > > + * Whether the object is currently in fake offset mmap backed by
> > > > vram.
> > > > + */
> > > > + unsigned int vram_userfault_count;
> > > > + struct list_head vram_userfault_link;
> > > > +
> > > > };
> > > >
> > > > #endif
> > > > diff --git a/drivers/gpu/drm/xe/xe_device_types.h
> > > > b/drivers/gpu/drm/xe/xe_device_types.h
> > > > index 750e1f0d3339..c345fb483af1 100644
> > > > --- a/drivers/gpu/drm/xe/xe_device_types.h
> > > > +++ b/drivers/gpu/drm/xe/xe_device_types.h
> > > > @@ -328,6 +328,26 @@ struct xe_device {
> > > > struct {
> > > > /** @ref: ref count of memory accesses */
> > > > atomic_t ref;
> > > > + /*
> > > > + * Protects access to vram usefault list.
> > > > + * It is required, if we are outside of the runtime suspend
> > > > path,
> > > > + * access to @vram_userfault_list requires always first
> > > > grabbing the
> > > > + * runtime pm, to ensure we can't race against runtime
> > > > suspend.
> > > > + * Once we have that we also need to grab
> > > > @vram_userfault_lock,
> > > > + * at which point we have exclusive access.
> > > > + * The runtime suspend path is special since it doesn't really
> > > > hold any locks,
> > > > + * but instead has exclusive access by virtue of all other
> > > > accesses requiring
> > > > + * holding the runtime pm wakeref.
> > > > + */
> > > > + spinlock_t vram_userfault_lock;
> > > > +
> > > > + /*
> > > > + * Keep list of userfaulted gem obj, which require to release
> > > > their
> > > > + * mmap mappings at runtime suspend path.
> > > > + */
> > > > + struct list_head vram_userfault_list;
> > > > +
> > > > + bool vram_userfault_ongoing;
> > > > } mem_access;
> > > >
> > > > /** @d3cold: Encapsulate d3cold related stuff */ diff --git
> > > > a/drivers/gpu/drm/xe/xe_pm.c b/drivers/gpu/drm/xe/xe_pm.c index
> > > > 0f06d8304e17..51cde1db930e 100644
> > > > --- a/drivers/gpu/drm/xe/xe_pm.c
> > > > +++ b/drivers/gpu/drm/xe/xe_pm.c
> > > > @@ -172,6 +172,8 @@ void xe_pm_init(struct xe_device *xe)
> > > > }
> > > >
> > > > xe_pm_runtime_init(xe);
> > > > + INIT_LIST_HEAD(&xe->mem_access.vram_userfault_list);
> > > > + spin_lock_init(&xe->mem_access.vram_userfault_lock);
> > > > }
> > > >
> > > > void xe_pm_runtime_fini(struct xe_device *xe) @@ -205,6 +207,7
> > > > @@ struct task_struct *xe_pm_read_callback_task(struct xe_device
> > > > *xe)
> > > >
> > > > int xe_pm_runtime_suspend(struct xe_device *xe) {
> > > > + struct xe_bo *bo, *on;
> > > > struct xe_gt *gt;
> > > > u8 id;
> > > > int err = 0;
> > > > @@ -238,6 +241,10 @@ int xe_pm_runtime_suspend(struct xe_device
> *xe)
> > > > */
> > > > lock_map_acquire(&xe_device_mem_access_lockdep_map);
> > > >
> > > > + list_for_each_entry_safe(bo, on,
> > > > + &xe->mem_access.vram_userfault_list,
> > > > vram_userfault_link)
> > > > + xe_bo_runtime_pm_release_mmap_offset(bo);
> > > > +
> > > > if (xe->d3cold.allowed) {
> > > > err = xe_bo_evict_all(xe);
> > > > if (err)
> > > > --
> > > > 2.25.1
> > >
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