From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ralph Campbell Subject: Re: [PATCH 3/4] mm: simplify device private page handling in hmm_range_fault Date: Mon, 16 Mar 2020 15:49:51 -0700 Message-ID: <7256f88d-809e-4aba-3c46-a223bd8cc521@nvidia.com> References: <20200316193216.920734-1-hch@lst.de> <20200316193216.920734-4-hch@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20200316193216.920734-4-hch-jcswGhMUV9g@public.gmane.org> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: amd-gfx-bounces-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org Sender: "amd-gfx" To: Christoph Hellwig , Jason Gunthorpe , Dan Williams , Bharata B Rao , =?UTF-8?Q?Christian_K=c3=b6nig?= , Ben Skeggs Cc: kvm-ppc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, nouveau-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Jerome Glisse , amd-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org List-Id: nouveau.vger.kernel.org On 3/16/20 12:32 PM, Christoph Hellwig wrote: > Remove the code to fault device private pages back into system memory > that has never been used by any driver. Also replace the usage of the > HMM_PFN_DEVICE_PRIVATE flag in the pfns array with a simple > is_device_private_page check in nouveau. > > Signed-off-by: Christoph Hellwig Getting rid of HMM_PFN_DEVICE_PRIVATE seems reasonable to me since a driver can look at the struct page but what if a driver needs to fault in a page from another device's private memory? Should it call handle_mm_fault()? > --- > drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 1 - > drivers/gpu/drm/nouveau/nouveau_dmem.c | 5 +++-- > drivers/gpu/drm/nouveau/nouveau_svm.c | 1 - > include/linux/hmm.h | 2 -- > mm/hmm.c | 25 +++++-------------------- > 5 files changed, 8 insertions(+), 26 deletions(-) > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c > index dee446278417..90821ce5e6ca 100644 > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c > @@ -776,7 +776,6 @@ struct amdgpu_ttm_tt { > static const uint64_t hmm_range_flags[HMM_PFN_FLAG_MAX] = { > (1 << 0), /* HMM_PFN_VALID */ > (1 << 1), /* HMM_PFN_WRITE */ > - 0 /* HMM_PFN_DEVICE_PRIVATE */ > }; > > static const uint64_t hmm_range_values[HMM_PFN_VALUE_MAX] = { > diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c b/drivers/gpu/drm/nouveau/nouveau_dmem.c > index 0e36345d395c..edfd0805fba4 100644 > --- a/drivers/gpu/drm/nouveau/nouveau_dmem.c > +++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c > @@ -28,6 +28,7 @@ > > #include > #include > +#include > #include > #include > > @@ -692,9 +693,8 @@ nouveau_dmem_convert_pfn(struct nouveau_drm *drm, > if (page == NULL) > continue; > > - if (!(range->pfns[i] & range->flags[HMM_PFN_DEVICE_PRIVATE])) { > + if (!is_device_private_page(page)) > continue; > - } > > if (!nouveau_dmem_page(drm, page)) { > WARN(1, "Some unknown device memory !\n"); > @@ -705,5 +705,6 @@ nouveau_dmem_convert_pfn(struct nouveau_drm *drm, > addr = nouveau_dmem_page_addr(page); > range->pfns[i] &= ((1UL << range->pfn_shift) - 1); > range->pfns[i] |= (addr >> PAGE_SHIFT) << range->pfn_shift; > + range->pfns[i] |= NVIF_VMM_PFNMAP_V0_VRAM; > } > } > diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c > index df9bf1fd1bc0..39c731a99937 100644 > --- a/drivers/gpu/drm/nouveau/nouveau_svm.c > +++ b/drivers/gpu/drm/nouveau/nouveau_svm.c > @@ -367,7 +367,6 @@ static const u64 > nouveau_svm_pfn_flags[HMM_PFN_FLAG_MAX] = { > [HMM_PFN_VALID ] = NVIF_VMM_PFNMAP_V0_V, > [HMM_PFN_WRITE ] = NVIF_VMM_PFNMAP_V0_W, > - [HMM_PFN_DEVICE_PRIVATE] = NVIF_VMM_PFNMAP_V0_VRAM, > }; > > static const u64 > diff --git a/include/linux/hmm.h b/include/linux/hmm.h > index 4bf8d6997b12..5e6034f105c3 100644 > --- a/include/linux/hmm.h > +++ b/include/linux/hmm.h > @@ -74,7 +74,6 @@ > * Flags: > * HMM_PFN_VALID: pfn is valid. It has, at least, read permission. > * HMM_PFN_WRITE: CPU page table has write permission set > - * HMM_PFN_DEVICE_PRIVATE: private device memory (ZONE_DEVICE) > * > * The driver provides a flags array for mapping page protections to device > * PTE bits. If the driver valid bit for an entry is bit 3, > @@ -86,7 +85,6 @@ > enum hmm_pfn_flag_e { > HMM_PFN_VALID = 0, > HMM_PFN_WRITE, > - HMM_PFN_DEVICE_PRIVATE, > HMM_PFN_FLAG_MAX > }; > > diff --git a/mm/hmm.c b/mm/hmm.c > index 180e398170b0..cfad65f6a67b 100644 > --- a/mm/hmm.c > +++ b/mm/hmm.c > @@ -118,15 +118,6 @@ static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk, > /* We aren't ask to do anything ... */ > if (!(pfns & range->flags[HMM_PFN_VALID])) > return; > - /* If this is device memory then only fault if explicitly requested */ > - if ((cpu_flags & range->flags[HMM_PFN_DEVICE_PRIVATE])) { > - /* Do we fault on device memory ? */ > - if (pfns & range->flags[HMM_PFN_DEVICE_PRIVATE]) { > - *write_fault = pfns & range->flags[HMM_PFN_WRITE]; > - *fault = true; > - } > - return; > - } > > /* If CPU page table is not valid then we need to fault */ > *fault = !(cpu_flags & range->flags[HMM_PFN_VALID]); > @@ -260,21 +251,15 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, > swp_entry_t entry = pte_to_swp_entry(pte); > > /* > - * This is a special swap entry, ignore migration, use > - * device and report anything else as error. > + * Never fault in device private pages pages, but just report > + * the PFN even if not present. > */ > if (is_device_private_entry(entry)) { > - cpu_flags = range->flags[HMM_PFN_VALID] | > - range->flags[HMM_PFN_DEVICE_PRIVATE]; > - cpu_flags |= is_write_device_private_entry(entry) ? > - range->flags[HMM_PFN_WRITE] : 0; > - hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags, > - &fault, &write_fault); > - if (fault || write_fault) > - goto fault; > *pfn = hmm_device_entry_from_pfn(range, > swp_offset(entry)); > - *pfn |= cpu_flags; > + *pfn |= range->flags[HMM_PFN_VALID]; > + if (is_write_device_private_entry(entry)) > + *pfn |= range->flags[HMM_PFN_WRITE]; > return 0; > } > >