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To:     Andrew Morton <akpm@linux-foundation.org>,
        John Hubbard <jhubbard@nvidia.com>
Cc:     Souptick Joarder <jrdr.linux@gmail.com>,
        Matthew Wilcox <willy@infradead.org>,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Tvrtko Ursulin <tvrtko.ursulin@intel.com>,
        Matthew Auld <matthew.auld@intel.com>,
        intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        LKML <linux-kernel@vger.kernel.org>, linux-mm@kvack.org,
        John Hubbard <jhubbard@nvidia.com>
From:   Chris Wilson <chris@chris-wilson.co.uk>
Subject: Re: [PATCH 0/4] mm/gup, drm/i915: refactor gup_fast, convert to pin_user_pages()
Message-ID: <159008745422.32320.5724805750977048669@build.alporthouse.com>
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Date:   Thu, 21 May 2020 19:57:34 +0100
Sender: linux-kernel-owner@vger.kernel.org
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Quoting John Hubbard (2020-05-19 01:21:20)
> This needs to go through Andrew's -mm tree, due to adding a new gup.c
> routine. However, I would really love to have some testing from the
> drm/i915 folks, because I haven't been able to run-time test that part
> of it.

CI hit

<4> [185.667750] WARNING: CPU: 0 PID: 1387 at mm/gup.c:2699 internal_get_user_pages_fast+0x63a/0xac0
<4> [185.667752] Modules linked in: vgem snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic i915 mei_hdcp x86_pkg_temp_thermal coretemp snd_hda_intel snd_intel_dspcfg crct10dif_pclmul snd_hda_codec crc32_pclmul snd_hwdep snd_hda_core ghash_clmulni_intel cdc_ether usbnet mii snd_pcm e1000e mei_me ptp pps_core mei intel_lpss_pci prime_numbers
<4> [185.667774] CPU: 0 PID: 1387 Comm: gem_userptr_bli Tainted: G     U            5.7.0-rc5-CI-Patchwork_17704+ #1
<4> [185.667777] Hardware name: Intel Corporation Ice Lake Client Platform/IceLake U DDR4 SODIMM PD RVP, BIOS ICLSFWR1.R00.3234.A01.1906141750 06/14/2019
<4> [185.667782] RIP: 0010:internal_get_user_pages_fast+0x63a/0xac0
<4> [185.667785] Code: 24 40 08 48 39 5c 24 38 49 89 df 0f 85 74 fc ff ff 48 83 44 24 50 08 48 39 5c 24 58 49 89 dc 0f 85 e0 fb ff ff e9 14 fe ff ff <0f> 0b b8 ea ff ff ff e9 36 fb ff ff 4c 89 e8 48 21 e8 48 39 e8 0f
<4> [185.667789] RSP: 0018:ffffc90001133c38 EFLAGS: 00010206
<4> [185.667792] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff8884999ee800
<4> [185.667795] RDX: 00000000000c0001 RSI: 0000000000000100 RDI: 00007f419e774000
<4> [185.667798] RBP: ffff888453dbf040 R08: 0000000000000000 R09: 0000000000000001
<4> [185.667800] R10: 0000000000000000 R11: 0000000000000000 R12: ffff888453dbf380
<4> [185.667803] R13: ffff8884999ee800 R14: ffff888453dbf3e8 R15: 0000000000000040
<4> [185.667806] FS:  00007f419e875e40(0000) GS:ffff88849fe00000(0000) knlGS:0000000000000000
<4> [185.667808] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
<4> [185.667811] CR2: 00007f419e873000 CR3: 0000000458bd2004 CR4: 0000000000760ef0
<4> [185.667814] PKRU: 55555554
<4> [185.667816] Call Trace:
<4> [185.667912]  ? i915_gem_userptr_get_pages+0x1c6/0x290 [i915]
<4> [185.667918]  ? mark_held_locks+0x49/0x70
<4> [185.667998]  ? i915_gem_userptr_get_pages+0x1c6/0x290 [i915]
<4> [185.668073]  ? i915_gem_userptr_get_pages+0x1c6/0x290 [i915]

and then panicked, across a range of systems.
-Chris