From: Ralph Campbell <rcampbell@nvidia.com>
To: "Christoph Hellwig" <hch@lst.de>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
"Dan Williams" <dan.j.williams@intel.com>,
"Bharata B Rao" <bharata@linux.ibm.com>,
"Christian König" <christian.koenig@amd.com>,
"Ben Skeggs" <bskeggs@redhat.com>
Cc: kvm-ppc@vger.kernel.org, nouveau@lists.freedesktop.org,
dri-devel@lists.freedesktop.org, linux-mm@kvack.org,
Jerome Glisse <jglisse@redhat.com>,
amd-gfx@lists.freedesktop.org
Subject: Re: [PATCH 3/4] mm: simplify device private page handling in hmm_range_fault
Date: Mon, 16 Mar 2020 15:49:51 -0700 [thread overview]
Message-ID: <7256f88d-809e-4aba-3c46-a223bd8cc521@nvidia.com> (raw)
In-Reply-To: <20200316193216.920734-4-hch@lst.de>
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 <hch@lst.de>
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 <nvif/class.h>
> #include <nvif/object.h>
> +#include <nvif/if000c.h>
> #include <nvif/if500b.h>
> #include <nvif/if900b.h>
>
> @@ -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;
> }
>
>
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next prev parent reply other threads:[~2020-03-16 22:50 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200316193216.920734-1-hch@lst.de>
[not found] ` <20200316193216.920734-2-hch@lst.de>
2020-03-16 20:55 ` [PATCH 1/4] memremap: add an owner field to struct dev_pagemap Ralph Campbell
[not found] ` <20200316193216.920734-3-hch@lst.de>
2020-03-16 21:43 ` [PATCH 2/4] mm: handle multiple owners of device private pages in migrate_vma Ralph Campbell
[not found] ` <20200316193216.920734-4-hch@lst.de>
2020-03-16 19:59 ` [PATCH 3/4] mm: simplify device private page handling in hmm_range_fault Jason Gunthorpe
2020-03-16 22:49 ` Ralph Campbell [this message]
2020-03-17 12:15 ` Jason Gunthorpe
[not found] ` <20200317122445.GA11662@lst.de>
[not found] ` <20200317122813.GA11866@lst.de>
2020-03-17 12:47 ` Jason Gunthorpe
[not found] ` <20200317125955.GA12847@lst.de>
2020-03-17 17:32 ` Jason Gunthorpe
2020-03-17 23:14 ` Ralph Campbell
2020-03-19 18:17 ` Jason Gunthorpe
2020-03-19 22:56 ` Ralph Campbell
2020-03-20 0:03 ` Jason Gunthorpe
2020-03-20 0:14 ` Jason Gunthorpe
2020-03-20 1:33 ` Ralph Campbell
2020-03-20 12:58 ` Jason Gunthorpe
[not found] ` <20200317073454.GA5843@lst.de>
2020-03-17 22:43 ` Ralph Campbell
2020-03-19 0:28 ` ensure device private pages have an owner v2 Jason Gunthorpe
[not found] ` <20200319071633.GA32522@lst.de>
2020-03-19 11:50 ` Jason Gunthorpe
2020-03-19 18:50 ` Jason Gunthorpe
[not found] ` <20200316193216.920734-5-hch@lst.de>
2020-03-16 19:49 ` [PATCH 4/4] mm: check the device private page owner in hmm_range_fault Jason Gunthorpe
2020-03-16 23:11 ` Ralph Campbell
2020-03-20 13:41 ` Jason Gunthorpe
[not found] ` <20200321082236.GB28613@lst.de>
2020-03-21 12:38 ` Jason Gunthorpe
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