linux-kernel - Re: [PATCH hmm v2 4/5] mm/hmm: remove HMM_PFN

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Date:   Mon, 4 May 2020 17:23:46 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     Jason Gunthorpe <jgg@...pe.ca>, <linux-mm@...ck.org>,
        Ralph Campbell <rcampbell@...dia.com>
CC:     Alex Deucher <alexander.deucher@....com>,
        <amd-gfx@...ts.freedesktop.org>, Ben Skeggs <bskeggs@...hat.com>,
        Christian König <christian.koenig@....com>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>,
        <dri-devel@...ts.freedesktop.org>,
        Felix Kuehling <Felix.Kuehling@....com>,
        Christoph Hellwig <hch@....de>,
        <intel-gfx@...ts.freedesktop.org>,
        Jérôme Glisse <jglisse@...hat.com>,
        <linux-kernel@...r.kernel.org>,
        Niranjana Vishwanathapura <niranjana.vishwanathapura@...el.com>,
        <nouveau@...ts.freedesktop.org>,
        "Yang, Philip" <Philip.Yang@....com>
Subject: Re: [PATCH hmm v2 4/5] mm/hmm: remove HMM_PFN_SPECIAL

On 2020-05-01 11:20, Jason Gunthorpe wrote:
> From: Jason Gunthorpe <jgg@...lanox.com>
> 
> This is just an alias for HMM_PFN_ERROR, nothing cares that the error was
> because of a special page vs any other error case.

Reviewed-by: John Hubbard <jhubbard@...dia.com>

thanks,
-- 
John Hubbard
NVIDIA
> 
> Acked-by: Felix Kuehling <Felix.Kuehling@....com>
> Reviewed-by: Christoph Hellwig <hch@....de>
> Signed-off-by: Jason Gunthorpe <jgg@...lanox.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 1 -
>   drivers/gpu/drm/nouveau/nouveau_svm.c   | 1 -
>   include/linux/hmm.h                     | 8 --------
>   mm/hmm.c                                | 2 +-
>   4 files changed, 1 insertion(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 41ae7f96f48194..76b4a4fa39ed04 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -775,7 +775,6 @@ static const uint64_t hmm_range_flags[HMM_PFN_FLAG_MAX] = {
>   static const uint64_t hmm_range_values[HMM_PFN_VALUE_MAX] = {
>   	0xfffffffffffffffeUL, /* HMM_PFN_ERROR */
>   	0, /* HMM_PFN_NONE */
> -	0xfffffffffffffffcUL /* HMM_PFN_SPECIAL */
>   };
>   
>   /**
> diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
> index c68e9317cf0740..cf0d9bd61bebf9 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_svm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
> @@ -379,7 +379,6 @@ static const u64
>   nouveau_svm_pfn_values[HMM_PFN_VALUE_MAX] = {
>   	[HMM_PFN_ERROR  ] = ~NVIF_VMM_PFNMAP_V0_V,
>   	[HMM_PFN_NONE   ] =  NVIF_VMM_PFNMAP_V0_NONE,
> -	[HMM_PFN_SPECIAL] = ~NVIF_VMM_PFNMAP_V0_V,
>   };
>   
>   /* Issue fault replay for GPU to retry accesses that faulted previously. */
> diff --git a/include/linux/hmm.h b/include/linux/hmm.h
> index 0df27dd03d53d7..81c302c884c0e3 100644
> --- a/include/linux/hmm.h
> +++ b/include/linux/hmm.h
> @@ -44,10 +44,6 @@ enum hmm_pfn_flag_e {
>    * Flags:
>    * HMM_PFN_ERROR: corresponding CPU page table entry points to poisoned memory
>    * HMM_PFN_NONE: corresponding CPU page table entry is pte_none()
> - * HMM_PFN_SPECIAL: corresponding CPU page table entry is special; i.e., the
> - *      result of vmf_insert_pfn() or vm_insert_page(). Therefore, it should not
> - *      be mirrored by a device, because the entry will never have HMM_PFN_VALID
> - *      set and the pfn value is undefined.
>    *
>    * Driver provides values for none entry, error entry, and special entry.
>    * Driver can alias (i.e., use same value) error and special, but
> @@ -56,12 +52,10 @@ enum hmm_pfn_flag_e {
>    * HMM pfn value returned by hmm_vma_get_pfns() or hmm_vma_fault() will be:
>    * hmm_range.values[HMM_PFN_ERROR] if CPU page table entry is poisonous,
>    * hmm_range.values[HMM_PFN_NONE] if there is no CPU page table entry,
> - * hmm_range.values[HMM_PFN_SPECIAL] if CPU page table entry is a special one
>    */
>   enum hmm_pfn_value_e {
>   	HMM_PFN_ERROR,
>   	HMM_PFN_NONE,
> -	HMM_PFN_SPECIAL,
>   	HMM_PFN_VALUE_MAX
>   };
>   
> @@ -110,8 +104,6 @@ static inline struct page *hmm_device_entry_to_page(const struct hmm_range *rang
>   		return NULL;
>   	if (entry == range->values[HMM_PFN_ERROR])
>   		return NULL;
> -	if (entry == range->values[HMM_PFN_SPECIAL])
> -		return NULL;
>   	if (!(entry & range->flags[HMM_PFN_VALID]))
>   		return NULL;
>   	return pfn_to_page(entry >> range->pfn_shift);
> diff --git a/mm/hmm.c b/mm/hmm.c
> index f06bcac948a79b..2e975eedb14f89 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -301,7 +301,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
>   			pte_unmap(ptep);
>   			return -EFAULT;
>   		}
> -		*pfn = range->values[HMM_PFN_SPECIAL];
> +		*pfn = range->values[HMM_PFN_ERROR];
>   		return 0;
>   	}
>   
>