Re: [PATCH v6 20/21] PCI/P2PDMA: Introduce pci_mmap_p2pmem()

From: Logan Gunthorpe <logang@deltatee.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-block@vger.kernel.org, linux-pci@vger.kernel.org,
	linux-mm@kvack.org, iommu@lists.linux-foundation.org,
	"Stephen Bates" <sbates@raithlin.com>,
	"Christoph Hellwig" <hch@lst.de>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Christian König" <christian.koenig@amd.com>,
	"John Hubbard" <jhubbard@nvidia.com>,
	"Don Dutile" <ddutile@redhat.com>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Daniel Vetter" <daniel.vetter@ffwll.ch>,
	"Jakowski Andrzej" <andrzej.jakowski@intel.com>,
	"Minturn Dave B" <dave.b.minturn@intel.com>,
	"Jason Ekstrand" <jason@jlekstrand.net>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Xiong Jianxin" <jianxin.xiong@intel.com>,
	"Bjorn Helgaas" <helgaas@kernel.org>,
	"Ira Weiny" <ira.weiny@intel.com>,
	"Robin Murphy" <robin.murphy@arm.com>,
	"Martin Oliveira" <martin.oliveira@eideticom.com>,
	"Chaitanya Kulkarni" <ckulkarnilinux@gmail.com>,
	"Ralph Campbell" <rcampbell@nvidia.com>,
	"Bjorn Helgaas" <bhelgaas@google.com>
Subject: Re: [PATCH v6 20/21] PCI/P2PDMA: Introduce pci_mmap_p2pmem()
Date: Fri, 27 May 2022 09:35:07 -0600	[thread overview]
Message-ID: <a2590e27-41e8-59dc-3576-b5b8d716a198@deltatee.com> (raw)
In-Reply-To: <20220527125501.GD2960187@ziepe.ca>

On 2022-05-27 06:55, Jason Gunthorpe wrote:
> On Thu, Apr 07, 2022 at 09:47:16AM -0600, Logan Gunthorpe wrote:
>> +static void pci_p2pdma_unmap_mappings(void *data)
>> +{
>> +	struct pci_dev *pdev = data;
>> +	struct pci_p2pdma *p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);
>> +
>> +	/* Ensure no new pages can be allocated in mappings */
>> +	p2pdma->active = false;
>> +	synchronize_rcu();
>> +
>> +	unmap_mapping_range(p2pdma->inode->i_mapping, 0, 0, 1);
>> +
>> +	/*
>> +	 * On some architectures, TLB flushes are done with call_rcu()
>> +	 * so to ensure GUP fast is done with the pages, call synchronize_rcu()
>> +	 * before freeing them.
>> +	 */
>> +	synchronize_rcu();
>> +	pci_p2pdma_free_mappings(p2pdma->inode->i_mapping);
> 
> With the series from Felix getting close this should get updated to
> not set pte_devmap and use proper natural refcounting without any of
> this stuff.

Can you send a link? I'm not sure what you are referring to.

Thanks,

Logan