linux-kernel - Re: [PATCH v3 19/20] PCI/P2PDMA: introduce pci_mmap

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Message-ID: <20210928195518.GV3544071@ziepe.ca>
Date:   Tue, 28 Sep 2021 16:55:18 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Logan Gunthorpe <logang@...tatee.com>
Cc:     linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
        linux-block@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
        Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Christian König <christian.koenig@....com>,
        John Hubbard <jhubbard@...dia.com>,
        Don Dutile <ddutile@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Jakowski Andrzej <andrzej.jakowski@...el.com>,
        Minturn Dave B <dave.b.minturn@...el.com>,
        Jason Ekstrand <jason@...kstrand.net>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Xiong Jianxin <jianxin.xiong@...el.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Ira Weiny <ira.weiny@...el.com>,
        Robin Murphy <robin.murphy@....com>,
        Martin Oliveira <martin.oliveira@...eticom.com>,
        Chaitanya Kulkarni <ckulkarnilinux@...il.com>
Subject: Re: [PATCH v3 19/20] PCI/P2PDMA: introduce pci_mmap_p2pmem()

On Thu, Sep 16, 2021 at 05:40:59PM -0600, Logan Gunthorpe wrote:
> +int pci_mmap_p2pmem(struct pci_dev *pdev, struct vm_area_struct *vma)
> +{
> +	struct pci_p2pdma_map *pmap;
> +	struct pci_p2pdma *p2pdma;
> +	int ret;
> +
> +	/* prevent private mappings from being established */
> +	if ((vma->vm_flags & VM_MAYSHARE) != VM_MAYSHARE) {
> +		pci_info_ratelimited(pdev,
> +				     "%s: fail, attempted private mapping\n",
> +				     current->comm);
> +		return -EINVAL;
> +	}
> +
> +	pmap = pci_p2pdma_map_alloc(pdev, vma->vm_end - vma->vm_start);
> +	if (!pmap)
> +		return -ENOMEM;
> +
> +	rcu_read_lock();
> +	p2pdma = rcu_dereference(pdev->p2pdma);
> +	if (!p2pdma) {
> +		ret = -ENODEV;
> +		goto out;
> +	}
> +
> +	ret = simple_pin_fs(&pci_p2pdma_fs_type, &pci_p2pdma_fs_mnt,
> +			    &pci_p2pdma_fs_cnt);
> +	if (ret)
> +		goto out;
> +
> +	ihold(p2pdma->inode);
> +	pmap->inode = p2pdma->inode;
> +	rcu_read_unlock();
> +
> +	vma->vm_flags |= VM_MIXEDMAP;

Why is this a VM_MIXEDMAP? Everything fault sticks in here has a
struct page, right?

Jason