Re: [PATCH v2] drm/amdkfd: Use partial hmm page walk during buffer validation in SVM

["Chen, Xiaogang" <xiaogang.chen@xxxxxxx>]

On 12/5/2023 12:48 PM, Philip Yang wrote:
> On 2023-12-04 15:23, Xiaogang.Chen wrote:
> > From: Xiaogang Chen<xiaogang.chen@xxxxxxx>
> >
> > v2:
> > -not need calculate vram page number for new registered svm range, only
> > do it for split vram pages.
> >
> > SVM uses hmm page walk to valid buffer before map to gpu vm. After have partial
> > migration/mapping do validation on same vm range as migration/map do instead of
> > whole svm range that can be very large. This change is expected to improve svm
> > code performance.
>
> Seems we could calculate old, new prange->vram_pages inside 
> svm_range_split_pages, using dma_addr & SVM_RANGE_VRAM_DOMAIN to 
> decide if it is vram or system memory pages. This will cover both 
> unmap from cpu and set_attr to split range cases, Thet the new 
> function svm_range_vram_pages is not needed.
ok, I use dma address to calculate split svm range vram page number, 
kfdtest passed. The new v3 patch includes it.
> prange->vram_pages update after migrating to vram should use mpages, 
> not cpages, the total collected pages.
It is from original code that used cpages as mpages. I think 
svm_migrate_successful_pages does not give correct migrate page number, 
then the original code used cpages. I updated this part by using 
svm_migrate_unsuccessful_pages, then mpages = cpages - 
svm_migrate_unsuccessful_pages(&migrate). The new v3 patch also includes 
this change. Please review it.

Regards

Xiaogang

> Regards,
>
> Philip
>
> > Signed-off-by: Xiaogang Chen<Xiaogang.Chen@xxxxxxx>
> > ---
> >   drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 149 ++++++++++++++++++++-------
> >   1 file changed, 109 insertions(+), 40 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> > index 2834fb351818..2f14cd1a3416 100644
> > --- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> > +++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> > @@ -158,13 +158,12 @@ svm_is_valid_dma_mapping_addr(struct device *dev, dma_addr_t dma_addr)
> >   static int
> >   svm_range_dma_map_dev(struct amdgpu_device *adev, struct svm_range *prange,
> >   		      unsigned long offset, unsigned long npages,
> > -		      unsigned long *hmm_pfns, uint32_t gpuidx, uint64_t *vram_pages)
> > +		      unsigned long *hmm_pfns, uint32_t gpuidx)
> >   {
> >   	enum dma_data_direction dir = DMA_BIDIRECTIONAL;
> >   	dma_addr_t *addr = prange->dma_addr[gpuidx];
> >   	struct device *dev = adev->dev;
> >   	struct page *page;
> > -	uint64_t vram_pages_dev;
> >   	int i, r;
> >   
> >   	if (!addr) {
> > @@ -174,7 +173,6 @@ svm_range_dma_map_dev(struct amdgpu_device *adev, struct svm_range *prange,
> >   		prange->dma_addr[gpuidx] = addr;
> >   	}
> >   
> > -	vram_pages_dev = 0;
> >   	addr += offset;
> >   	for (i = 0; i < npages; i++) {
> >   		if (svm_is_valid_dma_mapping_addr(dev, addr[i]))
> > @@ -184,7 +182,6 @@ svm_range_dma_map_dev(struct amdgpu_device *adev, struct svm_range *prange,
> >   		if (is_zone_device_page(page)) {
> >   			struct amdgpu_device *bo_adev = prange->svm_bo->node->adev;
> >   
> > -			vram_pages_dev++;
> >   			addr[i] = (hmm_pfns[i] << PAGE_SHIFT) +
> >   				   bo_adev->vm_manager.vram_base_offset -
> >   				   bo_adev->kfd.pgmap.range.start;
> > @@ -201,14 +198,14 @@ svm_range_dma_map_dev(struct amdgpu_device *adev, struct svm_range *prange,
> >   		pr_debug_ratelimited("dma mapping 0x%llx for page addr 0x%lx\n",
> >   				     addr[i] >> PAGE_SHIFT, page_to_pfn(page));
> >   	}
> > -	*vram_pages = vram_pages_dev;
> > +
> >   	return 0;
> >   }
> >   
> >   static int
> >   svm_range_dma_map(struct svm_range *prange, unsigned long *bitmap,
> >   		  unsigned long offset, unsigned long npages,
> > -		  unsigned long *hmm_pfns, uint64_t *vram_pages)
> > +		  unsigned long *hmm_pfns)
> >   {
> >   	struct kfd_process *p;
> >   	uint32_t gpuidx;
> > @@ -227,7 +224,7 @@ svm_range_dma_map(struct svm_range *prange, unsigned long *bitmap,
> >   		}
> >   
> >   		r = svm_range_dma_map_dev(pdd->dev->adev, prange, offset, npages,
> > -					  hmm_pfns, gpuidx, vram_pages);
> > +					  hmm_pfns, gpuidx);
> >   		if (r)
> >   			break;
> >   	}
> > @@ -982,11 +979,6 @@ svm_range_split_nodes(struct svm_range *new, struct svm_range *old,
> >   	new->svm_bo = svm_range_bo_ref(old->svm_bo);
> >   	new->ttm_res = old->ttm_res;
> >   
> > -	/* set new's vram_pages as old range's now, the acurate vram_pages
> > -	 * will be updated during mapping
> > -	 */
> > -	new->vram_pages = min(old->vram_pages, new->npages);
> > -
> >   	spin_lock(&new->svm_bo->list_lock);
> >   	list_add(&new->svm_bo_list, &new->svm_bo->range_list);
> >   	spin_unlock(&new->svm_bo->list_lock);
> > @@ -1107,9 +1099,9 @@ svm_range_split(struct svm_range *prange, uint64_t start, uint64_t last,
> >   
> >   static int
> >   svm_range_split_tail(struct svm_range *prange, uint64_t new_last,
> > -		     struct list_head *insert_list, struct list_head *remap_list)
> > +		     struct list_head *insert_list, struct list_head *remap_list,
> > +		     struct svm_range *tail)
> >   {
> > -	struct svm_range *tail;
> >   	int r = svm_range_split(prange, prange->start, new_last, &tail);
> >   
> >   	if (!r) {
> > @@ -1122,9 +1114,9 @@ svm_range_split_tail(struct svm_range *prange, uint64_t new_last,
> >   
> >   static int
> >   svm_range_split_head(struct svm_range *prange, uint64_t new_start,
> > -		     struct list_head *insert_list, struct list_head *remap_list)
> > +		     struct list_head *insert_list, struct list_head *remap_list,
> > +		     struct svm_range *head)
> >   {
> > -	struct svm_range *head;
> >   	int r = svm_range_split(prange, new_start, prange->last, &head);
> >   
> >   	if (!r) {
> > @@ -1573,7 +1565,6 @@ static int svm_range_validate_and_map(struct mm_struct *mm,
> >   	struct svm_validate_context *ctx;
> >   	unsigned long start, end, addr;
> >   	struct kfd_process *p;
> > -	uint64_t vram_pages;
> >   	void *owner;
> >   	int32_t idx;
> >   	int r = 0;
> > @@ -1642,15 +1633,13 @@ static int svm_range_validate_and_map(struct mm_struct *mm,
> >   		}
> >   	}
> >   
> > -	vram_pages = 0;
> > -	start = prange->start << PAGE_SHIFT;
> > -	end = (prange->last + 1) << PAGE_SHIFT;
> > +	start = map_start << PAGE_SHIFT;
> > +	end = (map_last + 1) << PAGE_SHIFT;
> >   	for (addr = start; !r && addr < end; ) {
> >   		struct hmm_range *hmm_range;
> >   		unsigned long map_start_vma;
> >   		unsigned long map_last_vma;
> >   		struct vm_area_struct *vma;
> > -		uint64_t vram_pages_vma;
> >   		unsigned long next = 0;
> >   		unsigned long offset;
> >   		unsigned long npages;
> > @@ -1677,13 +1666,11 @@ static int svm_range_validate_and_map(struct mm_struct *mm,
> >   		}
> >   
> >   		if (!r) {
> > -			offset = (addr - start) >> PAGE_SHIFT;
> > +			offset = (addr - (prange->start << PAGE_SHIFT)) >> PAGE_SHIFT;
> >   			r = svm_range_dma_map(prange, ctx->bitmap, offset, npages,
> > -					      hmm_range->hmm_pfns, &vram_pages_vma);
> > +					      hmm_range->hmm_pfns);
> >   			if (r)
> >   				pr_debug("failed %d to dma map range\n", r);
> > -			else
> > -				vram_pages += vram_pages_vma;
> >   		}
> >   
> >   		svm_range_lock(prange);
> > @@ -1716,19 +1703,6 @@ static int svm_range_validate_and_map(struct mm_struct *mm,
> >   		addr = next;
> >   	}
> >   
> > -	if (addr == end) {
> > -		prange->vram_pages = vram_pages;
> > -
> > -		/* if prange does not include any vram page and it
> > -		 * has not released svm_bo drop its svm_bo reference
> > -		 * and set its actaul_loc to sys ram
> > -		 */
> > -		if (!vram_pages && prange->ttm_res) {
> > -			prange->actual_loc = 0;
> > -			svm_range_vram_node_free(prange);
> > -		}
> > -	}
> > -
> >   	svm_range_unreserve_bos(ctx);
> >   	if (!r)
> >   		prange->validate_timestamp = ktime_get_boottime();
> > @@ -2037,6 +2011,81 @@ svm_range_split_new(struct svm_range_list *svms, uint64_t start, uint64_t last,
> >   	return 0;
> >   }
> >   
> > +static int
> > +svm_range_vram_pages(struct svm_range *prange)
> > +{
> > +	unsigned long start, end, addr;
> > +	struct svm_range_list *svms;
> > +	struct kfd_process *p;
> > +	struct mm_struct *mm;
> > +	struct page *page;
> > +	int32_t gpuidx;
> > +	void *owner;
> > +	int r = 0;
> > +
> > +	prange->vram_pages = 0;
> > +	svms = prange->svms;
> > +	p = container_of(svms, struct kfd_process, svms);
> > +	mm = get_task_mm(p->lead_thread);
> > +	if (!mm) {
> > +		pr_debug("svms 0x%p process mm gone\n", svms);
> > +		return -ESRCH;
> > +	}
> > +
> > +	/* prange->actual_loc should not be 0 here */
> > +	gpuidx = kfd_process_gpuidx_from_gpuid(p, prange->actual_loc);
> > +	if (gpuidx < 0) {
> > +		pr_debug("failed get device by id 0x%x\n", prange->actual_loc);
> > +		return -EINVAL;
> > +	}
> > +	owner = kfd_svm_page_owner(p, gpuidx);
> > +
> > +	start = prange->start << PAGE_SHIFT;
> > +	end = (prange->last + 1) << PAGE_SHIFT;
> > +	for (addr = start; addr < end; ) {
> > +		struct hmm_range *hmm_range;
> > +		struct vm_area_struct *vma;
> > +		unsigned long next = 0;
> > +		unsigned long npages;
> > +		bool readonly;
> > +
> > +		vma = vma_lookup(mm, addr);
> > +		if (!vma) {
> > +			mmput(mm);
> > +			return -EFAULT;
> > +		}
> > +
> > +		readonly = !(vma->vm_flags & VM_WRITE);
> > +		next = min(vma->vm_end, end);
> > +		npages = (next - addr) >> PAGE_SHIFT;
> > +		r = amdgpu_hmm_range_get_pages(&prange->notifier, addr, npages,
> > +					       readonly, owner, NULL,
> > +					       &hmm_range);
> > +		if (r) {
> > +			pr_debug("failed %d to get svm range pages\n", r);
> > +			mmput(mm);
> > +			return r;
> > +		}
> > +
> > +		for (int i = 0; i < npages; i++) {
> > +			page = hmm_pfn_to_page(hmm_range->hmm_pfns[i]);
> > +			if (is_zone_device_page(page))
> > +				prange->vram_pages++;
> > +		}
> > +
> > +		if (amdgpu_hmm_range_get_pages_done(hmm_range)) {
> > +			pr_debug("hmm update the range, need validate again\n");
> > +			mmput(mm);
> > +			return -EAGAIN;
> > +		}
> > +
> > +		addr = next;
> > +	}
> > +
> > +	mmput(mm);
> > +	return 0;
> > +}
> > +
> >   /**
> >    * svm_range_add - add svm range and handle overlap
> >    * @p: the range add to this process svms
> > @@ -2109,6 +2158,7 @@ svm_range_add(struct kfd_process *p, uint64_t start, uint64_t size,
> >   			 * will change. Clone and split it, apply updates only
> >   			 * to the overlapping part
> >   			 */
> > +			struct svm_range *head, *tail;
> >   			struct svm_range *old = prange;
> >   
> >   			prange = svm_range_clone(old);
> > @@ -2123,18 +2173,37 @@ svm_range_add(struct kfd_process *p, uint64_t start, uint64_t size,
> >   
> >   			if (node->start < start) {
> >   				pr_debug("change old range start\n");
> > +				head = NULL;
> >   				r = svm_range_split_head(prange, start,
> > -							 insert_list, remap_list);
> > +							 insert_list, remap_list, head);
> >   				if (r)
> >   					goto out;
> >   			}
> >   			if (node->last > last) {
> >   				pr_debug("change old range last\n");
> > +				tail = NULL;
> >   				r = svm_range_split_tail(prange, last,
> > -							 insert_list, remap_list);
> > +							 insert_list, remap_list, tail);
> >   				if (r)
> >   					goto out;
> >   			}
> > +			/* cal each inserted svn pragen vram_pages */
> > +			if (prange->actual_loc && prange->ttm_res) {
> > +
> > +				if (head) {
> > +					r = svm_range_vram_pages(head);
> > +					if (r)
> > +						return r;
> > +					prange->vram_pages = prange->vram_pages  - head->vram_pages;
> > +				}
> > +
> > +				if (tail) {
> > +					r = svm_range_vram_pages(tail);
> > +					if (r)
> > +						return  r;
> > +					prange->vram_pages = prange->vram_pages - tail->vram_pages;
> > +				}
> > +			}
> >   		} else {
> >   			/* The node is contained within start..last,
> >   			 * just update it