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From: John Hubbard <jhubbard@nvidia.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Al Viro" <viro@zeniv.linux.org.uk>,
	"Alex Williamson" <alex.williamson@redhat.com>,
	"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
	"Björn Töpel" <bjorn.topel@intel.com>,
	"Christoph Hellwig" <hch@infradead.org>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Daniel Vetter" <daniel@ffwll.ch>,
	"Dave Chinner" <david@fromorbit.com>,
	"David Airlie" <airlied@linux.ie>,
	"David S . Miller" <davem@davemloft.net>,
	"Ira Weiny" <ira.weiny@intel.com>, "Jan Kara" <jack@suse.cz>,
	"Jason Gunthorpe" <jgg@ziepe.ca>, "Jens Axboe" <axboe@kernel.dk>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Magnus Karlsson" <magnus.karlsson@intel.com>,
	"Mauro Carvalho Chehab" <mchehab@kernel.org>,
	"Michael Ellerman" <mpe@ellerman.id.au>,
	"Michal Hocko" <mhocko@suse.com>,
	"Mike Kravetz" <mike.kravetz@oracle.com>,
	"Paul Mackerras" <paulus@samba.org>,
	"Shuah Khan" <shuah@kernel.org>,
	"Vlastimil Babka" <vbabka@suse.cz>,
	bpf@vger.kernel.org, dri-devel@lists.freedesktop.org,
	kvm@vger.kernel.org, linux-block@vger.kernel.org,
	linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-kselftest@vger.kernel.org, linux-media@vger.kernel.org,
	linux-rdma@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	netdev@vger.kernel.org, linux-mm@kvack.org,
	LKML <linux-kernel@vger.kernel.org>,
	"John Hubbard" <jhubbard@nvidia.com>,
	"Jason Gunthorpe" <jgg@mellanox.com>
Subject: [PATCH 06/19] vfio: fix FOLL_LONGTERM use, simplify get_user_pages_remote() call
Date: Sun, 24 Nov 2019 20:19:58 -0800	[thread overview]
Message-ID: <20191125042011.3002372-7-jhubbard@nvidia.com> (raw)
In-Reply-To: <20191125042011.3002372-1-jhubbard@nvidia.com>

Update VFIO to take advantage of the recently loosened restriction on
FOLL_LONGTERM with get_user_pages_remote(). Also, now it is possible to
fix a bug: the VFIO caller is logically a FOLL_LONGTERM user, but it
wasn't setting FOLL_LONGTERM.

Also, remove an unnessary pair of calls that were releasing and
reacquiring the mmap_sem. There is no need to avoid holding mmap_sem
just in order to call page_to_pfn().

Also, now that the the DAX check ("if a VMA is DAX, don't allow long
term pinning") is in the internals of get_user_pages_remote() and
__gup_longterm_locked(), there's no need for it at the VFIO call site.
So remove it.

Tested-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/vfio/vfio_iommu_type1.c | 30 +++++-------------------------
 1 file changed, 5 insertions(+), 25 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 2ada8e6cdb88..b800fc9a0251 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -322,7 +322,6 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,
 {
 	struct page *page[1];
 	struct vm_area_struct *vma;
-	struct vm_area_struct *vmas[1];
 	unsigned int flags = 0;
 	int ret;
 
@@ -330,33 +329,14 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,
 		flags |= FOLL_WRITE;
 
 	down_read(&mm->mmap_sem);
-	if (mm == current->mm) {
-		ret = get_user_pages(vaddr, 1, flags | FOLL_LONGTERM, page,
-				     vmas);
-	} else {
-		ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags, page,
-					    vmas, NULL);
-		/*
-		 * The lifetime of a vaddr_get_pfn() page pin is
-		 * userspace-controlled. In the fs-dax case this could
-		 * lead to indefinite stalls in filesystem operations.
-		 * Disallow attempts to pin fs-dax pages via this
-		 * interface.
-		 */
-		if (ret > 0 && vma_is_fsdax(vmas[0])) {
-			ret = -EOPNOTSUPP;
-			put_page(page[0]);
-		}
-	}
-	up_read(&mm->mmap_sem);
-
+	ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags | FOLL_LONGTERM,
+				    page, NULL, NULL);
 	if (ret == 1) {
 		*pfn = page_to_pfn(page[0]);
-		return 0;
+		ret = 0;
+		goto done;
 	}
 
-	down_read(&mm->mmap_sem);
-
 	vaddr = untagged_addr(vaddr);
 
 	vma = find_vma_intersection(mm, vaddr, vaddr + 1);
@@ -366,7 +346,7 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,
 		if (is_invalid_reserved_pfn(*pfn))
 			ret = 0;
 	}
-
+done:
 	up_read(&mm->mmap_sem);
 	return ret;
 }
-- 
2.24.0


  parent reply	other threads:[~2019-11-25  4:22 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-25  4:19 [PATCH 00/19] pin_user_pages(): reduced-risk series for Linux 5.5 John Hubbard
2019-11-25  4:19 ` [PATCH 01/19] mm/gup: factor out duplicate code from four routines John Hubbard
2019-11-25  4:19 ` [PATCH 02/19] mm/gup: move try_get_compound_head() to top, fix minor issues John Hubbard
2019-11-25  4:19 ` [PATCH 03/19] mm: Cleanup __put_devmap_managed_page() vs ->page_free() John Hubbard
2019-11-25  4:19 ` [PATCH 04/19] goldish_pipe: rename local pin_user_pages() routine John Hubbard
2019-11-25  4:19 ` [PATCH 05/19] mm: fix get_user_pages_remote()'s handling of FOLL_LONGTERM John Hubbard
2019-11-25  4:19 ` John Hubbard [this message]
2019-11-25  4:19 ` [PATCH 07/19] mm/gup: introduce pin_user_pages*() and FOLL_PIN John Hubbard
2019-11-25  7:47   ` kbuild test robot
2019-11-25  8:44   ` kbuild test robot
2019-11-25 20:13     ` John Hubbard
2019-11-25  4:20 ` [PATCH 08/19] goldish_pipe: convert to pin_user_pages() and put_user_page() John Hubbard
2019-11-25  4:20 ` [PATCH 09/19] IB/{core,hw,umem}: set FOLL_PIN via pin_user_pages*(), fix up ODP John Hubbard
2019-11-25  4:20 ` [PATCH 10/19] mm/process_vm_access: set FOLL_PIN via pin_user_pages_remote() John Hubbard
2019-11-25  4:20 ` [PATCH 11/19] drm/via: set FOLL_PIN via pin_user_pages_fast() John Hubbard
2019-11-25  4:20 ` [PATCH 12/19] fs/io_uring: set FOLL_PIN via pin_user_pages() John Hubbard
2019-11-25  4:20 ` [PATCH 13/19] net/xdp: " John Hubbard
2019-11-25  4:20 ` [PATCH 14/19] media/v4l2-core: set pages dirty upon releasing DMA buffers John Hubbard
2019-11-25  4:20 ` [PATCH 15/19] media/v4l2-core: pin_user_pages (FOLL_PIN) and put_user_page() conversion John Hubbard
2019-11-25  4:20 ` [PATCH 16/19] vfio, mm: " John Hubbard
2019-11-25  4:20 ` [PATCH 17/19] powerpc: book3s64: convert to pin_user_pages() and put_user_page() John Hubbard
2019-11-25  8:59   ` Jan Kara
2019-11-25 20:46     ` John Hubbard
2019-11-25  4:20 ` [PATCH 18/19] mm/gup_benchmark: use proper FOLL_WRITE flags instead of hard-coding "1" John Hubbard
2019-11-25  4:20 ` [PATCH 19/19] mm, tree-wide: rename put_user_page*() to unpin_user_page*() John Hubbard

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