From: Christoph Hellwig <hch@lst.de>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-mm@kvack.org, "Ralph Campbell" <rcampbell@nvidia.com>,
"Alex Deucher" <alexander.deucher@amd.com>,
amd-gfx@lists.freedesktop.org, "Ben Skeggs" <bskeggs@redhat.com>,
"Christian König" <christian.koenig@amd.com>,
"David (ChunMing) Zhou" <David1.Zhou@amd.com>,
dri-devel@lists.freedesktop.org, "Kuehling,
Felix" <Felix.Kuehling@amd.com>, "Christoph Hellwig" <hch@lst.de>,
intel-gfx@lists.freedesktop.org,
"Jérôme Glisse" <jglisse@redhat.com>,
"John Hubbard" <jhubbard@nvidia.com>,
linux-kernel@vger.kernel.org,
"Niranjana Vishwanathapura" <niranjana.vishwanathapura@intel.com>,
nouveau@lists.freedesktop.org
Subject: Re: [PATCH hmm 2/5] mm/hmm: make hmm_range_fault return 0 or -1
Date: Wed, 22 Apr 2020 07:52:29 +0200 [thread overview]
Message-ID: <20200422055229.GB22366@lst.de> (raw)
In-Reply-To: <2-v1-4eb72686de3c+5062-hmm_no_flags_jgg@mellanox.com>
On Tue, Apr 21, 2020 at 09:21:43PM -0300, Jason Gunthorpe wrote:
> From: Jason Gunthorpe <jgg@mellanox.com>
>
> hmm_vma_walk->last is supposed to be updated after every write to the
> pfns, so that it can be returned by hmm_range_fault(). However, this is
> not done consistently. Fortunately nothing checks the return code of
> hmm_range_fault() for anything other than error.
>
> More importantly last must be set before returning -EBUSY as it is used to
> prevent reading an output pfn as an input flags when the loop restarts.
>
> For clarity and simplicity make hmm_range_fault() return 0 or -ERRNO. Only
> set last when returning -EBUSY.
>
> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
> ---
> Documentation/vm/hmm.rst | 2 +-
> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 4 ++--
> drivers/gpu/drm/nouveau/nouveau_svm.c | 6 +++---
> include/linux/hmm.h | 2 +-
> mm/hmm.c | 25 +++++++++----------------
> 5 files changed, 16 insertions(+), 23 deletions(-)
>
> diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst
> index 4e3e9362afeb10..9924f2caa0184c 100644
> --- a/Documentation/vm/hmm.rst
> +++ b/Documentation/vm/hmm.rst
> @@ -161,7 +161,7 @@ device must complete the update before the driver callback returns.
> When the device driver wants to populate a range of virtual addresses, it can
> use::
>
> - long hmm_range_fault(struct hmm_range *range);
> + int hmm_range_fault(struct hmm_range *range);
>
> It will trigger a page fault on missing or read-only entries if write access is
> requested (see below). Page faults use the generic mm page fault code path just
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 6309ff72bd7876..efc1329a019127 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -852,12 +852,12 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
> down_read(&mm->mmap_sem);
> r = hmm_range_fault(range);
> up_read(&mm->mmap_sem);
> - if (unlikely(r <= 0)) {
> + if (unlikely(r)) {
> /*
> * FIXME: This timeout should encompass the retry from
> * mmu_interval_read_retry() as well.
> */
> - if ((r == 0 || r == -EBUSY) && !time_after(jiffies, timeout))
> + if ((r == -EBUSY) && !time_after(jiffies, timeout))
Please also kill the superflous inner braces here.
> + * Return: 0 or -ERRNO with one of the following status codes:
Maybe say something like:
* Returns 0 on success or one of the following error codes:
Otherwise this looks good:
Reviewed-by: Christoph Hellwig <hch@lst.de>
next prev parent reply other threads:[~2020-04-22 5:52 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-22 0:21 [PATCH hmm 0/5] Adjust hmm_range_fault() API Jason Gunthorpe
2020-04-22 0:21 ` [PATCH hmm 1/5] mm/hmm: make CONFIG_DEVICE_PRIVATE into a select Jason Gunthorpe
2020-04-22 5:50 ` Christoph Hellwig
2020-04-22 0:21 ` [PATCH hmm 2/5] mm/hmm: make hmm_range_fault return 0 or -1 Jason Gunthorpe
2020-04-22 5:52 ` Christoph Hellwig [this message]
2020-04-29 19:38 ` Jason Gunthorpe
2020-04-22 0:21 ` [PATCH hmm 3/5] drm/amdgpu: remove dead code after hmm_range_fault() Jason Gunthorpe
2020-04-22 0:21 ` [PATCH hmm 4/5] mm/hmm: remove HMM_PFN_SPECIAL Jason Gunthorpe
2020-04-22 5:53 ` Christoph Hellwig
2020-04-22 0:21 ` [PATCH hmm 5/5] mm/hmm: remove the customizable pfn format from hmm_range_fault Jason Gunthorpe
2020-04-22 6:03 ` Christoph Hellwig
2020-04-22 12:39 ` Jason Gunthorpe
2020-04-23 6:10 ` Christoph Hellwig
2020-04-22 17:52 ` Felix Kuehling
2020-04-29 22:41 ` Jason Gunthorpe
2020-04-22 19:09 ` [PATCH hmm 0/5] Adjust hmm_range_fault() API Ralph Campbell
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