linux-kernel - Re: [PATCH v2] nouveau/hmm: map pages after migration

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Date:   Tue, 3 Mar 2020 08:42:29 -0400
From:   Jason Gunthorpe <jgg@...lanox.com>
To:     Ralph Campbell <rcampbell@...dia.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-rdma@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        nouveau@...ts.freedesktop.org, Jerome Glisse <jglisse@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Christoph Hellwig <hch@....de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ben Skeggs <bskeggs@...hat.com>
Subject: Re: [PATCH v2] nouveau/hmm: map pages after migration

On Mon, Mar 02, 2020 at 05:00:23PM -0800, Ralph Campbell wrote:
> When memory is migrated to the GPU, it is likely to be accessed by GPU
> code soon afterwards. Instead of waiting for a GPU fault, map the
> migrated memory into the GPU page tables with the same access permissions
> as the source CPU page table entries. This preserves copy on write
> semantics.
> 
> Signed-off-by: Ralph Campbell <rcampbell@...dia.com>
> Cc: Christoph Hellwig <hch@....de>
> Cc: Jason Gunthorpe <jgg@...lanox.com>
> Cc: "Jérôme Glisse" <jglisse@...hat.com>
> Cc: Ben Skeggs <bskeggs@...hat.com>
> ---
> 
> Originally this patch was targeted for Jason's rdma tree since other HMM
> related changes were queued there. Now that those have been merged, this
> patch just contains changes to nouveau so it could go through any tree.
> I guess Ben Skeggs' tree would be appropriate.

Yep

> +static inline struct nouveau_pfnmap_args *
> +nouveau_pfns_to_args(void *pfns)

don't use static inline inside C files

> +{
> +	struct nvif_vmm_pfnmap_v0 *p =
> +		container_of(pfns, struct nvif_vmm_pfnmap_v0, phys);
> +
> +	return container_of(p, struct nouveau_pfnmap_args, p);

And this should just be 

   return container_of(pfns, struct nouveau_pfnmap_args, p.phys);

> +static struct nouveau_svmm *
> +nouveau_find_svmm(struct nouveau_svm *svm, struct mm_struct *mm)
> +{
> +	struct nouveau_ivmm *ivmm;
> +
> +	list_for_each_entry(ivmm, &svm->inst, head) {
> +		if (ivmm->svmm->notifier.mm == mm)
> +			return ivmm->svmm;
> +	}
> +	return NULL;
> +}

Is this re-implementing mmu_notifier_get() ?

Jason