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From: Jason Gunthorpe <jgg@ziepe.ca>
To: Jerome Glisse <jglisse@redhat.com>
Cc: "John Hubbard" <jhubbard@nvidia.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"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>,
	"Jens Axboe" <axboe@kernel.dk>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"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>,
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	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>
Subject: Re: [PATCH v2 05/18] mm/gup: introduce pin_user_pages*() and FOLL_PIN
Date: Mon, 4 Nov 2019 16:37:02 -0400
Message-ID: <20191104203702.GG30938@ziepe.ca> (raw)
In-Reply-To: <20191104203153.GB7731@redhat.com>

On Mon, Nov 04, 2019 at 03:31:53PM -0500, Jerome Glisse wrote:
> > Note for Jason: the (a) or (b) items are talking about the vfio case, which is
> > one of the two call sites that now use pin_longterm_pages_remote(), and the
> > other one is infiniband:
> > 
> > drivers/infiniband/core/umem_odp.c:646:         npages = pin_longterm_pages_remote(owning_process, owning_mm,
> > drivers/vfio/vfio_iommu_type1.c:353:            ret = pin_longterm_pages_remote(NULL, mm, vaddr, 1,
> 
> vfio should be reverted until it can be properly implemented.
> The issue is that when you fix the implementation you might
> break vfio existing user and thus regress the kernel from user
> point of view. So i rather have the change to vfio reverted,
> i believe it was not well understood when it got upstream,
> between in my 5.4 tree it is still gup_remote not longterm.

It is clearly a bug, vfio must use LONGTERM, and does right above this
remote call:

        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);


I'm not even sure that it really makes any sense to build a 'if' like
that, surely just always call remote??

Jason

  reply index

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-03 21:17 [PATCH v2 00/18] mm/gup: track dma-pinned pages: FOLL_PIN, FOLL_LONGTERM John Hubbard
2019-11-03 21:17 ` [PATCH v2 01/18] mm/gup: pass flags arg to __gup_device_* functions John Hubbard
2019-11-04 16:39   ` Jerome Glisse
2019-11-03 21:17 ` [PATCH v2 02/18] mm/gup: factor out duplicate code from four routines John Hubbard
2019-11-04 16:51   ` Jerome Glisse
2019-11-03 21:17 ` [PATCH v2 03/18] goldish_pipe: rename local pin_user_pages() routine John Hubbard
2019-11-04 16:52   ` Jerome Glisse
2019-11-03 21:17 ` [PATCH v2 04/18] media/v4l2-core: set pages dirty upon releasing DMA buffers John Hubbard
2019-11-10 10:10   ` Hans Verkuil
2019-11-11 21:46     ` John Hubbard
2019-11-03 21:18 ` [PATCH v2 05/18] mm/gup: introduce pin_user_pages*() and FOLL_PIN John Hubbard
2019-11-04 17:33   ` Jerome Glisse
2019-11-04 19:04     ` John Hubbard
2019-11-04 19:18       ` Jerome Glisse
2019-11-04 19:30         ` John Hubbard
2019-11-04 19:52           ` Jerome Glisse
2019-11-04 20:09             ` John Hubbard
2019-11-04 20:31               ` Jason Gunthorpe
2019-11-04 20:40                 ` John Hubbard
2019-11-04 20:31               ` Jerome Glisse
2019-11-04 20:37                 ` Jason Gunthorpe [this message]
2019-11-04 20:57                   ` John Hubbard
2019-11-04 21:15                     ` Jason Gunthorpe
2019-11-04 21:34                       ` John Hubbard
2019-11-04 20:33   ` David Rientjes
2019-11-04 20:48     ` Jerome Glisse
2019-11-05 13:10   ` Mike Rapoport
2019-11-05 19:00     ` John Hubbard
2019-11-07  2:25       ` Ira Weiny
2019-11-07  8:07       ` Mike Rapoport
2019-11-03 21:18 ` [PATCH v2 06/18] goldish_pipe: convert to pin_user_pages() and put_user_page() John Hubbard
2019-11-03 21:18 ` [PATCH v2 07/18] infiniband: set FOLL_PIN, FOLL_LONGTERM via pin_longterm_pages*() John Hubbard
2019-11-04 20:33   ` Jason Gunthorpe
2019-11-04 20:48     ` John Hubbard
2019-11-04 20:57       ` Jason Gunthorpe
2019-11-04 22:03         ` John Hubbard
2019-11-05  2:32           ` Jason Gunthorpe
2019-11-07  2:26         ` Ira Weiny
2019-11-03 21:18 ` [PATCH v2 08/18] mm/process_vm_access: set FOLL_PIN via pin_user_pages_remote() John Hubbard
2019-11-04 17:41   ` Jerome Glisse
2019-11-03 21:18 ` [PATCH v2 09/18] drm/via: set FOLL_PIN via pin_user_pages_fast() John Hubbard
2019-11-04 17:44   ` Jerome Glisse
2019-11-04 18:22     ` John Hubbard
2019-11-03 21:18 ` [PATCH v2 10/18] fs/io_uring: set FOLL_PIN via pin_user_pages() John Hubbard
2019-11-03 21:18 ` [PATCH v2 11/18] net/xdp: " John Hubbard
2019-11-03 21:18 ` [PATCH v2 12/18] mm/gup: track FOLL_PIN pages John Hubbard
2019-11-04 18:52   ` Jerome Glisse
2019-11-04 22:49     ` John Hubbard
2019-11-04 23:49       ` Jerome Glisse
2019-11-05  0:18         ` John Hubbard
2019-11-03 21:18 ` [PATCH v2 13/18] media/v4l2-core: pin_longterm_pages (FOLL_PIN) and put_user_page() conversion John Hubbard
2019-11-10 10:11   ` Hans Verkuil
2019-11-03 21:18 ` [PATCH v2 14/18] vfio, mm: " John Hubbard
2019-11-03 21:18 ` [PATCH v2 15/18] powerpc: book3s64: convert to pin_longterm_pages() and put_user_page() John Hubbard
2019-11-03 21:18 ` [PATCH v2 16/18] mm/gup_benchmark: support pin_user_pages() and related calls John Hubbard
2019-11-03 21:18 ` [PATCH v2 17/18] selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN coverage John Hubbard
2019-11-03 21:18 ` [PATCH v2 18/18] mm/gup: remove support for gup(FOLL_LONGTERM) John Hubbard

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