[PATCH] drm/amdkfd: Use partial migrations in GPU page faults
Felix Kuehling
felix.kuehling at amd.com
Thu Aug 31 18:00:30 UTC 2023
On 2023-08-30 19:02, Chen, Xiaogang wrote:
>
> On 8/30/2023 3:56 PM, Felix Kuehling wrote:
>>
>> On 2023-08-30 15:39, Chen, Xiaogang wrote:
>>>
>>> On 8/28/2023 5:37 PM, Felix Kuehling wrote:
>>>>
>>>> On 2023-08-28 16:57, Chen, Xiaogang wrote:
>>>>>
>>>>> On 8/28/2023 2:06 PM, Felix Kuehling wrote:
>>>>>>
>>>>>> On 2023-08-24 18:08, Xiaogang.Chen wrote:
>>>>>>> From: Xiaogang Chen <xiaogang.chen at amd.com>
>>>>>>>
>>>>>>> This patch implements partial migration in gpu page fault
>>>>>>> according to migration
>>>>>>> granularity(default 2MB) and not split svm range in cpu page
>>>>>>> fault handling.
>>>>>>> Now a svm range may have pages from both system ram and vram of
>>>>>>> one gpu.
>>>>>>> These chagnes are expected to improve migration performance and
>>>>>>> reduce
>>>>>>> mmu callback and TLB flush workloads.
>>>>>>>
>>>>>>> Signed-off-by: xiaogang chen <xiaogang.chen at amd.com>
>>>>>>> ---
>>>>>>> drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 153
>>>>>>> +++++++++++++++--------
>>>>>>> drivers/gpu/drm/amd/amdkfd/kfd_migrate.h | 6 +-
>>>>>>> drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 87 ++++++++-----
>>>>>>> drivers/gpu/drm/amd/amdkfd/kfd_svm.h | 7 +-
>>>>>>> 4 files changed, 162 insertions(+), 91 deletions(-)
>>>>>>>
>>>>>>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
>>>>>>> b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
>>>>>>> index 7d82c7da223a..5a3aa80a1834 100644
>>>>>>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
>>>>>>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
>>>>>>> @@ -479,6 +479,8 @@ svm_migrate_vma_to_vram(struct kfd_node
>>>>>>> *node, struct svm_range *prange,
>>>>>>> * svm_migrate_ram_to_vram - migrate svm range from system to
>>>>>>> device
>>>>>>> * @prange: range structure
>>>>>>> * @best_loc: the device to migrate to
>>>>>>> + * @start_mgr: start page to migrate
>>>>>>> + * @last_mgr: last page to migrate
>>>>>>> * @mm: the process mm structure
>>>>>>> * @trigger: reason of migration
>>>>>>> *
>>>>>>> @@ -489,6 +491,7 @@ svm_migrate_vma_to_vram(struct kfd_node
>>>>>>> *node, struct svm_range *prange,
>>>>>>> */
>>>>>>> static int
>>>>>>> svm_migrate_ram_to_vram(struct svm_range *prange, uint32_t
>>>>>>> best_loc,
>>>>>>> + unsigned long start_mgr, unsigned long last_mgr,
>>>>>>> struct mm_struct *mm, uint32_t trigger)
>>>>>>> {
>>>>>>> unsigned long addr, start, end;
>>>>>>> @@ -498,9 +501,9 @@ svm_migrate_ram_to_vram(struct svm_range
>>>>>>> *prange, uint32_t best_loc,
>>>>>>> unsigned long cpages = 0;
>>>>>>> long r = 0;
>>>>>>> - if (prange->actual_loc == best_loc) {
>>>>>>> - pr_debug("svms 0x%p [0x%lx 0x%lx] already on best_loc
>>>>>>> 0x%x\n",
>>>>>>> - prange->svms, prange->start, prange->last, best_loc);
>>>>>>> + if (!best_loc) {
>>>>>>> + pr_debug("request svms 0x%p [0x%lx 0x%lx] migrate to
>>>>>>> sys ram\n",
>>>>>>> + prange->svms, start_mgr, last_mgr);
>>>>>>> return 0;
>>>>>>> }
>>>>>>> @@ -513,8 +516,8 @@ svm_migrate_ram_to_vram(struct svm_range
>>>>>>> *prange, uint32_t best_loc,
>>>>>>> pr_debug("svms 0x%p [0x%lx 0x%lx] to gpu 0x%x\n",
>>>>>>> prange->svms,
>>>>>>> prange->start, prange->last, best_loc);
>>>>>>> - start = prange->start << PAGE_SHIFT;
>>>>>>> - end = (prange->last + 1) << PAGE_SHIFT;
>>>>>>> + start = start_mgr << PAGE_SHIFT;
>>>>>>> + end = (last_mgr + 1) << PAGE_SHIFT;
>>>>>>> r = svm_range_vram_node_new(node, prange, true);
>>>>>>> if (r) {
>>>>>>> @@ -544,10 +547,12 @@ svm_migrate_ram_to_vram(struct svm_range
>>>>>>> *prange, uint32_t best_loc,
>>>>>>> if (cpages) {
>>>>>>> prange->actual_loc = best_loc;
>>>>>>> - svm_range_free_dma_mappings(prange, true);
>>>>>>> - } else {
>>>>>>> + /* only free dma mapping in the migrated range */
>>>>>>> + svm_range_free_dma_mappings(prange, true, start_mgr -
>>>>>>> prange->start,
>>>>>>> + last_mgr - start_mgr + 1);
>>>>>>
>>>>>> This is wrong. If we only migrated some of the pages, we should
>>>>>> not free the DMA mapping array at all. The array is needed as
>>>>>> long as there are any valid DMA mappings in it.
>>>>>
>>>>> yes, I realized it after submit. I can not free DMA mapping array
>>>>> at this stage.
>>>>>
>>>>> The concern(also related to comments below) is I do not know how
>>>>> many pages in vram after partial migration. Originally I used
>>>>> bitmap to record that. I used bitmap to record which pages were
>>>>> migrated at each migration functions. Here I do not need use hmm
>>>>> function to get that info, inside each migration function we can
>>>>> know which pages got migrated, then update the bitmap accordingly
>>>>> inside each migration function.
>>>>>
>>>>>>
>>>>>> I think the condition above with cpages should be updated.
>>>>>> Instead of cpages, we need to keep track of a count of pages in
>>>>>> VRAM in struct svm_range. See more below.
>>>>>>
>>>>> I think you want add a new integer in svm_range to remember how
>>>>> many pages are in vram side for each svm_range, instead of bitmap.
>>>>> There is a problem I saw: when we need split a prange(such as user
>>>>> uses set_attr api) how do we know how many pages in vram for each
>>>>> splitted prange?
>>>>
>>>> Right, that's a bit problematic. But it should be a relatively rare
>>>> corner case. It may be good enough to make a "pessimistic"
>>>> assumption when splitting ranges that have some pages in VRAM, that
>>>> everything is in VRAM. And update that to 0 after migrate_to_ram
>>>> for the entire range, to allow the BO reference to be released.
>>>>
>>> migrate_to_ram is partial migration too that only 2MB vram got
>>> migrated. After split if we assume all pages are vram(pessimistic)
>>> we will give the new vram pages number as all page number(in each
>>> spitted prange). Then after 2MB vram migrated to ram, we still do
>>> not know if we can release BO reference for this prange as we gave
>>> vram page number in each spiltted prange(sub prange) more than it has.
>>
>> Right. I think we still have cases where we migrate entire ranges to
>> RAM, e.g. in svm_migrate_vram_to_vram. In those cases we could update
>> the counter to 0 and drop the BO reference even after splitting a range.
>>
>> Also, splitting ranges becomes more rare with your patch. The only
>> remaining scenarios that would split ranges are partial munmap of a
>> range, and changing attributes on partial ranges. If we want to
>> update the counters accurately after splitting the ranges, we could
>> just revalidate the entire ranges and update the counters in
>> svm_validate_and_map based on the page addresses returned by
>> hmm_range_fault. That avoids us having to track that information in
>> our own bitmaps.
>>
>>
> I think we need have accurate vram page number accurately since this
> number decides when a prange can call svm_range_vram_node_free to drop
> its reference to svm_bo.
>
> I think your way is possible that at each svm_range_validate_and_map
> we get this vram page number from hmm_pfn_to_page which tell us each
> page is device or sys ram page. We already use that to get dma address
> for each page, so it should not add overhead. That means: after split
> a prange may not have accurate vram page number, but after we map the
> prange we would get the accurate number. I think that it is ok since
> before gpu mapping the prange is not used actually, and we can release
> svm_bo after gpu mapping when find all pages are sys ram.
>
>>>
>>>> So in the worst case, you keep your DMA addresses and BOs allocated
>>>> slightly longer than necessary. If that doesn't work, I agree that
>>>> we need a bitmap with one bit per 4KB page. But I hope that can be
>>>> avoided.
>>>>
>>>> That said, I'm not actually sure why we're freeing the DMA address
>>>> array after migration to RAM at all. I think we still need it even
>>>> when we're using VRAM. We call svm_range_dma_map in
>>>> svm_range_validate_and_map regardless of whether the range is in
>>>> VRAM or system memory. So it will just allocate a new array the
>>>> next time the range is validated anyway. VRAM pages use a special
>>>> address encoding to indicate VRAM pages to the GPUVM code.
>>>
>>> I think we do not need free DMA address array as you said, it is
>>> another thing though.
>>>
>>> We need unmap dma address(dma_unmap_page) after migrate from ram to
>>> vram because we always do dma_map_page at
>>> svm_range_validate_and_map. If not we would have multiple dma maps
>>> for same sys ram page.
>>
>> svm_range_dma_map_dev calls dma_unmap_page before overwriting an
>> existing valid entry in the dma_addr array. Anyway, dma unmapping the
>> old pages in bulk may still be cleaner. And it avoids delays in
>> cleaning up DMA mappings after migrations.
>>
>> Regards,
>> Felix
>>
>>
> then we may not need do dma_unmap after migrate from ram to vram since
> svm_range_dma_map_dev always do dma_unmap_page if the address is valid
> dma address for sys ram, and after migrate from ram to vram we always
> do gpu mapping?
I think with XNACK enabled, the DMA mapping may be delayed until a page
fault. For example on a multi-GPU system, GPU1 page faults and migrates
data from system memory to its VRAM. Immediately afterwards, the page
fault handler should use svm_validate_and_map to update GPU1 page
tables. But GPU2 page tables are not updated immediately. So the now
stale DMA mappings for GPU2 would continue to exist until the next page
fault on GPU2.
Regards,
Felix
>
> Regards
>
> Xiaogang
>
>>> In partial migration(ram->vram) we can only unmap dma address for
>>> the pages that got migrated.
>>>
>>> Overall it not seems that using an item in svm_range to record how
>>> many vram page can solve spit prange case. Thought? or we talk offline.
>>>
>>> Regards
>>>
>>> Xiaogang
>>>
>>>>
>>>> Regards,
>>>> Felix
>>>>
>>>>
>>>>>
>>>>>>> + } else if (!prange->actual_loc)
>>>>>>> + /* if all pages from prange are at sys ram */
>>>>>>> svm_range_vram_node_free(prange);
>>>>>>> - }
>>>>>>> return r < 0 ? r : 0;
>>>>>>> }
>>>>>>> @@ -762,6 +767,8 @@ svm_migrate_vma_to_ram(struct kfd_node
>>>>>>> *node, struct svm_range *prange,
>>>>>>> * svm_migrate_vram_to_ram - migrate svm range from device to
>>>>>>> system
>>>>>>> * @prange: range structure
>>>>>>> * @mm: process mm, use current->mm if NULL
>>>>>>> + * @start_mgr: start page need be migrated to sys ram
>>>>>>> + * @last_mgr: last page need be migrated to sys ram
>>>>>>> * @trigger: reason of migration
>>>>>>> * @fault_page: is from vmf->page, svm_migrate_to_ram(), this
>>>>>>> is CPU page fault callback
>>>>>>> *
>>>>>>> @@ -771,7 +778,8 @@ svm_migrate_vma_to_ram(struct kfd_node
>>>>>>> *node, struct svm_range *prange,
>>>>>>> * 0 - OK, otherwise error code
>>>>>>> */
>>>>>>> int svm_migrate_vram_to_ram(struct svm_range *prange, struct
>>>>>>> mm_struct *mm,
>>>>>>> - uint32_t trigger, struct page *fault_page)
>>>>>>> + unsigned long start_mgr, unsigned long
>>>>>>> last_mgr,
>>>>>>> + uint32_t trigger, struct page *fault_page)
>>>>>>> {
>>>>>>> struct kfd_node *node;
>>>>>>> struct vm_area_struct *vma;
>>>>>>> @@ -781,23 +789,30 @@ int svm_migrate_vram_to_ram(struct
>>>>>>> svm_range *prange, struct mm_struct *mm,
>>>>>>> unsigned long upages = 0;
>>>>>>> long r = 0;
>>>>>>> + /* this pragne has no any vram page to migrate to sys ram */
>>>>>>> if (!prange->actual_loc) {
>>>>>>> pr_debug("[0x%lx 0x%lx] already migrated to ram\n",
>>>>>>> prange->start, prange->last);
>>>>>>> return 0;
>>>>>>> }
>>>>>>> + if (start_mgr < prange->start || last_mgr > prange->last) {
>>>>>>> + pr_debug("migration range [0x%lx 0x%lx] out prange
>>>>>>> [0x%lx 0x%lx]\n",
>>>>>>> + start_mgr, last_mgr, prange->start, prange->last);
>>>>>>> + return -EFAULT;
>>>>>>> + }
>>>>>>> +
>>>>>>> node = svm_range_get_node_by_id(prange, prange->actual_loc);
>>>>>>> if (!node) {
>>>>>>> pr_debug("failed to get kfd node by id 0x%x\n",
>>>>>>> prange->actual_loc);
>>>>>>> return -ENODEV;
>>>>>>> }
>>>>>>> pr_debug("svms 0x%p prange 0x%p [0x%lx 0x%lx] from gpu
>>>>>>> 0x%x to ram\n",
>>>>>>> - prange->svms, prange, prange->start, prange->last,
>>>>>>> + prange->svms, prange, start_mgr, last_mgr,
>>>>>>> prange->actual_loc);
>>>>>>> - start = prange->start << PAGE_SHIFT;
>>>>>>> - end = (prange->last + 1) << PAGE_SHIFT;
>>>>>>> + start = start_mgr << PAGE_SHIFT;
>>>>>>> + end = (last_mgr + 1) << PAGE_SHIFT;
>>>>>>> for (addr = start; addr < end;) {
>>>>>>> unsigned long next;
>>>>>>> @@ -822,8 +837,47 @@ int svm_migrate_vram_to_ram(struct
>>>>>>> svm_range *prange, struct mm_struct *mm,
>>>>>>> }
>>>>>>> if (r >= 0 && !upages) {
>>>>>>> - svm_range_vram_node_free(prange);
>>>>>>> - prange->actual_loc = 0;
>>>>>>> + /* all vram pages from prange got migrated to sys ram */
>>>>>>> + if (start_mgr == prange->start && last_mgr ==
>>>>>>> prange->last) {
>>>>>>> +
>>>>>>> + prange->actual_loc = 0;
>>>>>>> + spin_lock(&prange->svm_bo->list_lock);
>>>>>>> + list_del_init(&prange->svm_bo_list);
>>>>>>> + spin_unlock(&prange->svm_bo->list_lock);
>>>>>>> +
>>>>>>> + svm_range_vram_node_free(prange);
>>>>>>> + } else {
>>>>>>> +
>>>>>>> + /* cannot call svm_range_vram_node_free since only
>>>>>>> part of its vram
>>>>>>> + * pages got migrated. check if all vram pages from
>>>>>>> all pranges
>>>>>>> + * that shared this svm_bo have been released, then
>>>>>>> unref
>>>>>>> + * all svm_bo ref count.
>>>>>>
>>>>>> This feels wrong and I don't understand why it's necessary. The
>>>>>> point of ref counting is, that you don't need to know what the
>>>>>> other ranges are doing. Each range manages its own reference to
>>>>>> the BO. When it no longer needs the BO, it drops its reference.
>>>>>> When the ref count drops to 0, the BO gets freed.
>>>>>>
>>>>> As above: I did not know how many pages got migrated to sys ram in
>>>>> a prange if not remember that. So I counter ref count of svm_bo
>>>>> after each migration, when the counter reach to the prange(shared
>>>>> the svm_bo) number I release the svm_bo. It is how this awkward
>>>>> checking came. Before I used bitmap in each prange to record that,
>>>>> not need this kind checking. If use an integer for that I do not
>>>>> know how to handle prange split?
>>>>>
>>>>>>
>>>>>>> + */
>>>>>>> + struct svm_range *tmp;
>>>>>>> + unsigned int count = 0;
>>>>>>> +
>>>>>>> + /* how many prangs refer to this svm_bo */
>>>>>>> + spin_lock(&prange->svm_bo->list_lock);
>>>>>>> + list_for_each_entry(tmp,
>>>>>>> &prange->svm_bo->range_list, svm_bo_list)
>>>>>>> + count++;
>>>>>>> + spin_unlock(&prange->svm_bo->list_lock);
>>>>>>> +
>>>>>>> + /* if svm_bo ref number is same as count above all
>>>>>>> vram pages from
>>>>>>> + * all pranges have been released, unref svm_bo
>>>>>>> count times
>>>>>>> + * from all pranges to force svm_bo released
>>>>>>
>>>>>> There is probably a possible race condition here if a range gets
>>>>>> split concurrently. Or a page gets migrated between the ref count
>>>>>> check and taking the list_lock.
>>>>>>
>>>>>> A better way to handle this would not need to look at the other
>>>>>> ranges at all. What we really need to know is, how many pages of
>>>>>> this range are currently in VRAM. We should be able to track this
>>>>>> with a new counter in struct svm_range that gets incremented or
>>>>>> decremented by cpages at the end of every migration.
>>>>>>
>>>>>>> + */
>>>>>>> + if (refcount_read(&prange->svm_bo->kref.refcount)
>>>>>>> == count) {
>>>>>>> +
>>>>>>> + spin_lock(&prange->svm_bo->list_lock);
>>>>>>> + list_for_each_entry(tmp,
>>>>>>> &prange->svm_bo->range_list, svm_bo_list) {
>>>>>>> + spin_unlock(&prange->svm_bo->list_lock);
>>>>>>> +
>>>>>>> + svm_range_vram_node_free(tmp);
>>>>>>> + spin_lock(&prange->svm_bo->list_lock);
>>>>>>> + }
>>>>>>> + spin_unlock(&prange->svm_bo->list_lock);
>>>>>>> + }
>>>>>>> + }
>>>>>>> }
>>>>>>> return r < 0 ? r : 0;
>>>>>>> @@ -833,17 +887,23 @@ int svm_migrate_vram_to_ram(struct
>>>>>>> svm_range *prange, struct mm_struct *mm,
>>>>>>> * svm_migrate_vram_to_vram - migrate svm range from device to
>>>>>>> device
>>>>>>> * @prange: range structure
>>>>>>> * @best_loc: the device to migrate to
>>>>>>> + * @start: start page need be migrated to sys ram
>>>>>>> + * @last: last page need be migrated to sys ram
>>>>>>> * @mm: process mm, use current->mm if NULL
>>>>>>> * @trigger: reason of migration
>>>>>>> *
>>>>>>> * Context: Process context, caller hold mmap read lock, svms
>>>>>>> lock, prange lock
>>>>>>> *
>>>>>>> + * migrate all vram pages in prange to sys ram, then migrate
>>>>>>> [start, last] pages
>>>>>>> + * from sys ram to gpu node best_loc.
>>>>>>> + *
>>>>>>> * Return:
>>>>>>> * 0 - OK, otherwise error code
>>>>>>> */
>>>>>>> static int
>>>>>>> svm_migrate_vram_to_vram(struct svm_range *prange, uint32_t
>>>>>>> best_loc,
>>>>>>> - struct mm_struct *mm, uint32_t trigger)
>>>>>>> + unsigned long start, unsigned long last,
>>>>>>> + struct mm_struct *mm, uint32_t trigger)
>>>>>>> {
>>>>>>> int r, retries = 3;
>>>>>>> @@ -855,7 +915,8 @@ svm_migrate_vram_to_vram(struct svm_range
>>>>>>> *prange, uint32_t best_loc,
>>>>>>> pr_debug("from gpu 0x%x to gpu 0x%x\n",
>>>>>>> prange->actual_loc, best_loc);
>>>>>>> do {
>>>>>>> - r = svm_migrate_vram_to_ram(prange, mm, trigger, NULL);
>>>>>>> + r = svm_migrate_vram_to_ram(prange, mm, prange->start,
>>>>>>> prange->last,
>>>>>>> + trigger, NULL);
>>>>>>> if (r)
>>>>>>> return r;
>>>>>>> } while (prange->actual_loc && --retries);
>>>>>>> @@ -863,18 +924,20 @@ svm_migrate_vram_to_vram(struct svm_range
>>>>>>> *prange, uint32_t best_loc,
>>>>>>> if (prange->actual_loc)
>>>>>>> return -EDEADLK;
>>>>>>> - return svm_migrate_ram_to_vram(prange, best_loc, mm,
>>>>>>> trigger);
>>>>>>> + return svm_migrate_ram_to_vram(prange, best_loc, start,
>>>>>>> last, mm, trigger);
>>>>>>> }
>>>>>>> int
>>>>>>> svm_migrate_to_vram(struct svm_range *prange, uint32_t best_loc,
>>>>>>> - struct mm_struct *mm, uint32_t trigger)
>>>>>>> + unsigned long start, unsigned long last,
>>>>>>> + struct mm_struct *mm, uint32_t trigger)
>>>>>>> {
>>>>>>> - if (!prange->actual_loc)
>>>>>>> - return svm_migrate_ram_to_vram(prange, best_loc, mm,
>>>>>>> trigger);
>>>>>>> + if (!prange->actual_loc || prange->actual_loc == best_loc)
>>>>>>> + return svm_migrate_ram_to_vram(prange, best_loc, start,
>>>>>>> last,
>>>>>>> + mm, trigger);
>>>>>>> else
>>>>>>> - return svm_migrate_vram_to_vram(prange, best_loc, mm,
>>>>>>> trigger);
>>>>>>> -
>>>>>>> + return svm_migrate_vram_to_vram(prange, best_loc,
>>>>>>> start, last,
>>>>>>> + mm, trigger);
>>>>>>> }
>>>>>>> /**
>>>>>>> @@ -889,10 +952,9 @@ svm_migrate_to_vram(struct svm_range
>>>>>>> *prange, uint32_t best_loc,
>>>>>>> */
>>>>>>> static vm_fault_t svm_migrate_to_ram(struct vm_fault *vmf)
>>>>>>> {
>>>>>>> + unsigned long start, last, size;
>>>>>>> unsigned long addr = vmf->address;
>>>>>>> struct svm_range_bo *svm_bo;
>>>>>>> - enum svm_work_list_ops op;
>>>>>>> - struct svm_range *parent;
>>>>>>> struct svm_range *prange;
>>>>>>> struct kfd_process *p;
>>>>>>> struct mm_struct *mm;
>>>>>>> @@ -929,51 +991,34 @@ static vm_fault_t
>>>>>>> svm_migrate_to_ram(struct vm_fault *vmf)
>>>>>>> mutex_lock(&p->svms.lock);
>>>>>>> - prange = svm_range_from_addr(&p->svms, addr, &parent);
>>>>>>> + prange = svm_range_from_addr(&p->svms, addr, NULL);
>>>>>>> if (!prange) {
>>>>>>> pr_debug("failed get range svms 0x%p addr 0x%lx\n",
>>>>>>> &p->svms, addr);
>>>>>>> r = -EFAULT;
>>>>>>> goto out_unlock_svms;
>>>>>>> }
>>>>>>> - mutex_lock(&parent->migrate_mutex);
>>>>>>> - if (prange != parent)
>>>>>>> - mutex_lock_nested(&prange->migrate_mutex, 1);
>>>>>>> + mutex_lock(&prange->migrate_mutex);
>>>>>>> if (!prange->actual_loc)
>>>>>>> goto out_unlock_prange;
>>>>>>> - svm_range_lock(parent);
>>>>>>> - if (prange != parent)
>>>>>>> - mutex_lock_nested(&prange->lock, 1);
>>>>>>> - r = svm_range_split_by_granularity(p, mm, addr, parent,
>>>>>>> prange);
>>>>>>> - if (prange != parent)
>>>>>>> - mutex_unlock(&prange->lock);
>>>>>>> - svm_range_unlock(parent);
>>>>>>> - if (r) {
>>>>>>> - pr_debug("failed %d to split range by granularity\n", r);
>>>>>>> - goto out_unlock_prange;
>>>>>>> - }
>>>>>>> + /* Align migration range start and size to granularity size */
>>>>>>> + size = 1UL << prange->granularity;
>>>>>>> + start = ALIGN_DOWN(addr, size);
>>>>>>> + last = ALIGN(addr + 1, size) - 1;
>>>>>>> +
>>>>>>> + start = (start >= prange->start) ? start : prange->start;
>>>>>>> + last = (last <= prange->last) ? last : prange->last;
>>>>>>> - r = svm_migrate_vram_to_ram(prange, vmf->vma->vm_mm,
>>>>>>> - KFD_MIGRATE_TRIGGER_PAGEFAULT_CPU,
>>>>>>> - vmf->page);
>>>>>>> + r = svm_migrate_vram_to_ram(prange, vmf->vma->vm_mm, start,
>>>>>>> last,
>>>>>>> + KFD_MIGRATE_TRIGGER_PAGEFAULT_CPU, vmf->page);
>>>>>>> if (r)
>>>>>>> pr_debug("failed %d migrate svms 0x%p range 0x%p
>>>>>>> [0x%lx 0x%lx]\n",
>>>>>>> - r, prange->svms, prange, prange->start,
>>>>>>> prange->last);
>>>>>>> -
>>>>>>> - /* xnack on, update mapping on GPUs with ACCESS_IN_PLACE */
>>>>>>> - if (p->xnack_enabled && parent == prange)
>>>>>>> - op = SVM_OP_UPDATE_RANGE_NOTIFIER_AND_MAP;
>>>>>>> - else
>>>>>>> - op = SVM_OP_UPDATE_RANGE_NOTIFIER;
>>>>>>> - svm_range_add_list_work(&p->svms, parent, mm, op);
>>>>>>> - schedule_deferred_list_work(&p->svms);
>>>>>>> + r, prange->svms, prange, start, last);
>>>>>>> out_unlock_prange:
>>>>>>> - if (prange != parent)
>>>>>>> - mutex_unlock(&prange->migrate_mutex);
>>>>>>> - mutex_unlock(&parent->migrate_mutex);
>>>>>>> + mutex_unlock(&prange->migrate_mutex);
>>>>>>> out_unlock_svms:
>>>>>>> mutex_unlock(&p->svms.lock);
>>>>>>> out_unref_process:
>>>>>>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.h
>>>>>>> b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.h
>>>>>>> index 487f26368164..9e48d10e848e 100644
>>>>>>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.h
>>>>>>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.h
>>>>>>> @@ -41,9 +41,13 @@ enum MIGRATION_COPY_DIR {
>>>>>>> };
>>>>>>> int svm_migrate_to_vram(struct svm_range *prange, uint32_t
>>>>>>> best_loc,
>>>>>>> + unsigned long start, unsigned long last,
>>>>>>> struct mm_struct *mm, uint32_t trigger);
>>>>>>> +
>>>>>>> int svm_migrate_vram_to_ram(struct svm_range *prange, struct
>>>>>>> mm_struct *mm,
>>>>>>> - uint32_t trigger, struct page *fault_page);
>>>>>>> + unsigned long start, unsigned long last,
>>>>>>> + uint32_t trigger, struct page *fault_page);
>>>>>>> +
>>>>>>> unsigned long
>>>>>>> svm_migrate_addr_to_pfn(struct amdgpu_device *adev, unsigned
>>>>>>> long addr);
>>>>>>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
>>>>>>> b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
>>>>>>> index 841ba6102bbb..012dceb7c0ed 100644
>>>>>>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
>>>>>>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
>>>>>>> @@ -247,7 +247,8 @@ void svm_range_dma_unmap(struct device *dev,
>>>>>>> dma_addr_t *dma_addr,
>>>>>>> }
>>>>>>> }
>>>>>>> -void svm_range_free_dma_mappings(struct svm_range *prange,
>>>>>>> bool unmap_dma)
>>>>>>> +void svm_range_free_dma_mappings(struct svm_range *prange, bool
>>>>>>> unmap_dma,
>>>>>>> + unsigned long offset, unsigned long npages)
>>>>>>> {
>>>>>>> struct kfd_process_device *pdd;
>>>>>>> dma_addr_t *dma_addr;
>>>>>>> @@ -269,7 +270,7 @@ void svm_range_free_dma_mappings(struct
>>>>>>> svm_range *prange, bool unmap_dma)
>>>>>>> }
>>>>>>> dev = &pdd->dev->adev->pdev->dev;
>>>>>>> if (unmap_dma)
>>>>>>> - svm_range_dma_unmap(dev, dma_addr, 0, prange->npages);
>>>>>>> + svm_range_dma_unmap(dev, dma_addr, offset, npages);
>>>>>>> kvfree(dma_addr);
>>>>>>
>>>>>> This doesn't make sense. If we only unmapped some of the DMA
>>>>>> mappings, we should not free the DMA mapping array at all,
>>>>>> because that would mean leaking all the DMA mappings we did not
>>>>>> unmap.
>>>>> right, I realized that after submit. It is also related to able
>>>>> knowing if all pages are migrated to vram.
>>>>>>
>>>>>>> prange->dma_addr[gpuidx] = NULL;
>>>>>>> }
>>>>>>> @@ -284,7 +285,7 @@ static void svm_range_free(struct svm_range
>>>>>>> *prange, bool do_unmap)
>>>>>>> prange->start, prange->last);
>>>>>>> svm_range_vram_node_free(prange);
>>>>>>> - svm_range_free_dma_mappings(prange, do_unmap);
>>>>>>> + svm_range_free_dma_mappings(prange, do_unmap, 0,
>>>>>>> prange->npages);
>>>>>>> if (do_unmap && !p->xnack_enabled) {
>>>>>>> pr_debug("unreserve prange 0x%p size: 0x%llx\n",
>>>>>>> prange, size);
>>>>>>> @@ -384,6 +385,8 @@ static void svm_range_bo_release(struct kref
>>>>>>> *kref)
>>>>>>> prange->start, prange->last);
>>>>>>> mutex_lock(&prange->lock);
>>>>>>> prange->svm_bo = NULL;
>>>>>>> + /* prange dose not hold vram page now */
>>>>>>> + prange->actual_loc = 0;
>>>>>>
>>>>>> This is probably the wrong place to do this. The caller of
>>>>>> svm_range_bo_release should probably update prange->actual_loc
>>>>>> before calling this function.
>>>>>>
>>>>>>
>>>>>>> mutex_unlock(&prange->lock);
>>>>>>> spin_lock(&svm_bo->list_lock);
>>>>>>> @@ -439,7 +442,8 @@ svm_range_validate_svm_bo(struct kfd_node
>>>>>>> *node, struct svm_range *prange)
>>>>>>> mutex_unlock(&prange->lock);
>>>>>>> return false;
>>>>>>> }
>>>>>>> - if (prange->ttm_res) {
>>>>>>> + /* requeset from same kfd_node and we still have reference
>>>>>>> to it */
>>>>>>> + if (prange->ttm_res && prange->svm_bo->node == node) {
>>>>>>> /* We still have a reference, all is well */
>>>>>>> mutex_unlock(&prange->lock);
>>>>>>> return true;
>>>>>>> @@ -458,6 +462,8 @@ svm_range_validate_svm_bo(struct kfd_node
>>>>>>> *node, struct svm_range *prange)
>>>>>>> spin_unlock(&prange->svm_bo->list_lock);
>>>>>>> svm_range_bo_unref(prange->svm_bo);
>>>>>>> + prange->ttm_res = NULL;
>>>>>>> + prange->svm_bo = NULL;
>>>>>>
>>>>>> If this is really necessary, it should probably be done inside
>>>>>> the prange->lock.
>>>>>>
>>>>>>
>>>>>>> return false;
>>>>>>> }
>>>>>>> if (READ_ONCE(prange->svm_bo->evicting)) {
>>>>>>> @@ -2888,6 +2894,7 @@ svm_range_restore_pages(struct
>>>>>>> amdgpu_device *adev, unsigned int pasid,
>>>>>>> uint32_t vmid, uint32_t node_id,
>>>>>>> uint64_t addr, bool write_fault)
>>>>>>> {
>>>>>>> + unsigned long start, last, size;
>>>>>>> struct mm_struct *mm = NULL;
>>>>>>> struct svm_range_list *svms;
>>>>>>> struct svm_range *prange;
>>>>>>> @@ -3023,34 +3030,38 @@ svm_range_restore_pages(struct
>>>>>>> amdgpu_device *adev, unsigned int pasid,
>>>>>>> kfd_smi_event_page_fault_start(node, p->lead_thread->pid,
>>>>>>> addr,
>>>>>>> write_fault, timestamp);
>>>>>>> - if (prange->actual_loc != best_loc) {
>>>>>>> - migration = true;
>>>>>>> - if (best_loc) {
>>>>>>> - r = svm_migrate_to_vram(prange, best_loc, mm,
>>>>>>> - KFD_MIGRATE_TRIGGER_PAGEFAULT_GPU);
>>>>>>> - if (r) {
>>>>>>> - pr_debug("svm_migrate_to_vram failed (%d) at
>>>>>>> %llx, falling back to system memory\n",
>>>>>>> - r, addr);
>>>>>>> - /* Fallback to system memory if migration to
>>>>>>> - * VRAM failed
>>>>>>> - */
>>>>>>> - if (prange->actual_loc)
>>>>>>> - r = svm_migrate_vram_to_ram(prange, mm,
>>>>>>> - KFD_MIGRATE_TRIGGER_PAGEFAULT_GPU,
>>>>>>> - NULL);
>>>>>>> - else
>>>>>>> - r = 0;
>>>>>>> - }
>>>>>>> - } else {
>>>>>>> - r = svm_migrate_vram_to_ram(prange, mm,
>>>>>>> - KFD_MIGRATE_TRIGGER_PAGEFAULT_GPU,
>>>>>>> - NULL);
>>>>>>> - }
>>>>>>> + /* Align migration range start and size to granularity size */
>>>>>>> + size = 1UL << prange->granularity;
>>>>>>> + start = ALIGN_DOWN(addr, size);
>>>>>>> + last = ALIGN(addr + 1, size) - 1;
>>>>>>> +
>>>>>>> + start = (start >= prange->start) ? start : prange->start;
>>>>>>> + last = (last <= prange->last) ? last : prange->last;
>>>>>>
>>>>>> This could be written more compact:
>>>>>>
>>>>>> start = max(prange->start, ALIGN_DOWN(addr, size));
>>>>>> last = min(prange->last, ALIGN(addr + 1, size) - 1);
>>>>>>
>>>>>>
>>>>>>> +
>>>>>>> + migration = true;
>>>>>>
>>>>>> If you make this always true, we don't need this variable any
>>>>>> more. But see below ...
>>>>>>
>>>>>>
>>>>>>> + if (best_loc) {
>>>>>>> + r = svm_migrate_to_vram(prange, best_loc, start, last,
>>>>>>> + mm, KFD_MIGRATE_TRIGGER_PAGEFAULT_GPU);
>>>>>>
>>>>>> Maybe we can add an output parameter to svm_migrate_... to return
>>>>>> whether an actual migration was performed (based on cpages). That
>>>>>> could be used to update the migration variable more accurately.
>>>>>>
>>>>>>
>>>>>>> if (r) {
>>>>>>> - pr_debug("failed %d to migrate svms %p [0x%lx
>>>>>>> 0x%lx]\n",
>>>>>>> - r, svms, prange->start, prange->last);
>>>>>>> - goto out_unlock_range;
>>>>>>> + pr_debug("svm_migrate_to_vram failed (%d) at %llx,
>>>>>>> falling back to system memory\n",
>>>>>>> + r, addr);
>>>>>>> + /* Fallback to system memory if migration to
>>>>>>> + * VRAM failed
>>>>>>> + */
>>>>>>> + if (prange->actual_loc)
>>>>>>> + r = svm_migrate_vram_to_ram(prange, mm, start,
>>>>>>> last,
>>>>>>> + KFD_MIGRATE_TRIGGER_PAGEFAULT_GPU, NULL);
>>>>>>> + else
>>>>>>> + r = 0;
>>>>>>> }
>>>>>>> + } else {
>>>>>>> + r = svm_migrate_vram_to_ram(prange, mm, start, last,
>>>>>>> + KFD_MIGRATE_TRIGGER_PAGEFAULT_GPU, NULL);
>>>>>>
>>>>>> This is only necessary if prange->actual_loc is non-0. And again,
>>>>>> this could update migration with an output parameter based on
>>>>>> cpages.
>>>>>>
>>>>>>
>>>>>>> + }
>>>>>>> + if (r) {
>>>>>>> + pr_debug("failed %d to migrate svms %p [0x%lx 0x%lx]\n",
>>>>>>> + r, svms, start, last);
>>>>>>> + goto out_unlock_range;
>>>>>>> }
>>>>>>> r = svm_range_validate_and_map(mm, prange, gpuidx,
>>>>>>> false, false, false);
>>>>>>> @@ -3402,18 +3413,22 @@ svm_range_trigger_migration(struct
>>>>>>> mm_struct *mm, struct svm_range *prange,
>>>>>>> *migrated = false;
>>>>>>> best_loc = svm_range_best_prefetch_location(prange);
>>>>>>> - if (best_loc == KFD_IOCTL_SVM_LOCATION_UNDEFINED ||
>>>>>>> - best_loc == prange->actual_loc)
>>>>>>> + /* when best_loc is a gpu node and same as prange->actual_loc
>>>>>>> + * we still need migrate as prange->actual_loc does not
>>>>>>> mean all
>>>>>>> + * pages in prange are vram. hmm migrate will pick up right
>>>>>>> pages.
>>>>>>> + */
>>>>>>> + if (best_loc == KFD_IOCTL_SVM_LOCATION_UNDEFINED)
>>>>>>> return 0;
>>>>>>> if (!best_loc) {
>>>>>>> - r = svm_migrate_vram_to_ram(prange, mm,
>>>>>>> + r = svm_migrate_vram_to_ram(prange, mm, prange->start,
>>>>>>> prange->last,
>>>>>>> KFD_MIGRATE_TRIGGER_PREFETCH, NULL);
>>>>>>> *migrated = !r;
>>>>>>
>>>>>> This could also use an output parameter from
>>>>>> svm_migrate_vram_to_ram to update migrated more accurately.
>>>>>>
>>>>>> Regards,
>>>>>> Felix
>>>>>>
>>>>> I think the main issue here is to know how many pages are from
>>>>> vram for a prange. If use an integer to record how we handle
>>>>> prange split case?
>>>>>
>>>>> Regards
>>>>>
>>>>> Xiaogang
>>>>>
>>>>>>
>>>>>>> return r;
>>>>>>> }
>>>>>>> - r = svm_migrate_to_vram(prange, best_loc, mm,
>>>>>>> KFD_MIGRATE_TRIGGER_PREFETCH);
>>>>>>> + r = svm_migrate_to_vram(prange, best_loc, prange->start,
>>>>>>> prange->last,
>>>>>>> + mm, KFD_MIGRATE_TRIGGER_PREFETCH);
>>>>>>> *migrated = !r;
>>>>>>> return r;
>>>>>>> @@ -3468,7 +3483,11 @@ static void
>>>>>>> svm_range_evict_svm_bo_worker(struct work_struct *work)
>>>>>>> mutex_lock(&prange->migrate_mutex);
>>>>>>> do {
>>>>>>> + /* migrate all vram pages in this prange to sys ram
>>>>>>> + * after that prange->actual_loc should be zero
>>>>>>> + */
>>>>>>> r = svm_migrate_vram_to_ram(prange, mm,
>>>>>>> + prange->start, prange->last,
>>>>>>> KFD_MIGRATE_TRIGGER_TTM_EVICTION, NULL);
>>>>>>> } while (!r && prange->actual_loc && --retries);
>>>>>>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
>>>>>>> b/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
>>>>>>> index 9e668eeefb32..c565e018cfb3 100644
>>>>>>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
>>>>>>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
>>>>>>> @@ -88,7 +88,9 @@ struct svm_work_list_item {
>>>>>>> * @flags: flags defined as KFD_IOCTL_SVM_FLAG_*
>>>>>>> * @perferred_loc: perferred location, 0 for CPU, or GPU id
>>>>>>> * @perfetch_loc: last prefetch location, 0 for CPU, or GPU id
>>>>>>> - * @actual_loc: the actual location, 0 for CPU, or GPU id
>>>>>>> + * @actual_loc: this svm_range location. 0: all pages are from
>>>>>>> sys ram;
>>>>>>> + * GPU id: this svm_range may include vram pages
>>>>>>> from GPU with
>>>>>>> + * id actual_loc.
>>>>>>> * @granularity:migration granularity, log2 num pages
>>>>>>> * @invalid: not 0 means cpu page table is invalidated
>>>>>>> * @validate_timestamp: system timestamp when range is validated
>>>>>>> @@ -183,7 +185,8 @@ void svm_range_add_list_work(struct
>>>>>>> svm_range_list *svms,
>>>>>>> void schedule_deferred_list_work(struct svm_range_list *svms);
>>>>>>> void svm_range_dma_unmap(struct device *dev, dma_addr_t
>>>>>>> *dma_addr,
>>>>>>> unsigned long offset, unsigned long npages);
>>>>>>> -void svm_range_free_dma_mappings(struct svm_range *prange, bool
>>>>>>> unmap_dma);
>>>>>>> +void svm_range_free_dma_mappings(struct svm_range *prange, bool
>>>>>>> unmap_dma,
>>>>>>> + unsigned long offset, unsigned long npages);
>>>>>>> int svm_range_get_info(struct kfd_process *p, uint32_t
>>>>>>> *num_svm_ranges,
>>>>>>> uint64_t *svm_priv_data_size);
>>>>>>> int kfd_criu_checkpoint_svm(struct kfd_process *p,
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