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Janusz Krzysztofik 749670a58d
 Revert "drm/i915: Remove extra multi-gt pm-references" 
This reverts commit 1f33dc0c11.

There was a patch supposed to fix an issue of illegal attempts to free a
still active i915 VMA object when parking a GT believed to be idle,
reported by CI on 2-GT Meteor Lake.  As a solution, an extra wakeref for
a Primary GT was acquired from i915_gem_do_execbuffer() -- see commit
f56fe3e917 ("drm/i915: Fix a VMA UAF for multi-gt platform").

However, that fix occurred insufficient -- the issue was still reported by
CI.  That wakeref was released on exit from i915_gem_do_execbuffer(), then
potentially before completion of the request and deactivation of its
associated VMAs.  Moreover, CI reports indicated that single-GT platforms
also suffered sporadically from the same race.

Since that issue was fixed by another commit f3c71b2ded ("drm/i915/vma:
Fix UAF on destroy against retire race"), the changes introduced by that
insufficient fix were dropped as no longer useful.  However, that series
resulted in another VMA UAF scenario now being triggered in CI.

<4> [260.290809] ------------[ cut here ]------------
<4> [260.290988] list_del corruption. prev->next should be ffff888118c5d990, but was ffff888118c5a510. (prev=ffff888118c5a510)
<4> [260.291004] WARNING: CPU: 2 PID: 1143 at lib/list_debug.c:62 __list_del_entry_valid_or_report+0xb7/0xe0
..
<4> [260.291055] CPU: 2 PID: 1143 Comm: kms_plane Not tainted 6.9.0-rc2-CI_DRM_14524-ga25d180c6853+ #1
<4> [260.291058] Hardware name: Intel Corporation Meteor Lake Client Platform/MTL-P LP5x T3 RVP, BIOS MTLPFWI1.R00.3471.D91.2401310918 01/31/2024
<4> [260.291060] RIP: 0010:__list_del_entry_valid_or_report+0xb7/0xe0
...
<4> [260.291087] Call Trace:
<4> [260.291089]  <TASK>
<4> [260.291124]  i915_vma_reopen+0x43/0x80 [i915]
<4> [260.291298]  eb_lookup_vmas+0x9cb/0xcc0 [i915]
<4> [260.291579]  i915_gem_do_execbuffer+0xc9a/0x26d0 [i915]
<4> [260.291883]  i915_gem_execbuffer2_ioctl+0x123/0x2a0 [i915]
...
<4> [260.292301]  </TASK>
...
<4> [260.292506] ---[ end trace 0000000000000000 ]---
<4> [260.292782] general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6ca3: 0000 [#1] PREEMPT SMP NOPTI
<4> [260.303575] CPU: 2 PID: 1143 Comm: kms_plane Tainted: G        W          6.9.0-rc2-CI_DRM_14524-ga25d180c6853+ #1
<4> [260.313851] Hardware name: Intel Corporation Meteor Lake Client Platform/MTL-P LP5x T3 RVP, BIOS MTLPFWI1.R00.3471.D91.2401310918 01/31/2024
<4> [260.326359] RIP: 0010:eb_validate_vmas+0x114/0xd80 [i915]
...
<4> [260.428756] Call Trace:
<4> [260.431192]  <TASK>
<4> [639.283393]  i915_gem_do_execbuffer+0xd05/0x26d0 [i915]
<4> [639.305245]  i915_gem_execbuffer2_ioctl+0x123/0x2a0 [i915]
...
<4> [639.411134]  </TASK>
...
<4> [639.449979] ---[ end trace 0000000000000000 ]---

We defer actually closing, unbinding and destroying a VMA until next idle
point, or until the object is freed in the meantime.  By postponing the
unbind, we allow for the VMA to be reopened by the client, avoiding the
work required to rebind the VMA.

Starting from commit b0647a5e79 ("drm/i915: Avoid live-lock with
i915_vma_parked()"), we assume that as long as a GT is held idle, no VMA
would be reopened while we destroy them.  That assumption is no longer
true in multi-GT configurations, where a VMA we reopen may be handled by a
GT different from the one that we already keep active via its engine while
we set up an execbuf request.

Restoring the extra GT0 PM wakeref removed from i915_gem_do_execbuffer()
processing path seems to fix this issue.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/10608
Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Nirmoy Das <nirmoy.das@linux.intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@linux.intel.com>
Fixes: 1f33dc0c11 ("drm/i915: Remove extra multi-gt pm-references")
Link: https://patchwork.freedesktop.org/patch/msgid/20240506180253.96858-2-janusz.krzysztofik@linux.intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
History 2024-05-07 13:09:03 -04:00
arch Linux 6.6-rc7 2023-10-23 18:20:06 +10:00
block block: Fix regression in sed-opal for a saved key. 2023-10-13 08:16:08 -06:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto KEYS: asymmetric: Fix sign/verify on pkcs1pad without a hash 2023-10-18 12:27:10 +08:00
Documentation Merge tag 'drm-msm-next-2023-10-17' of https://gitlab.freedesktop.org/drm/msm into drm-next 2023-10-23 18:29:18 +10:00
drivers Revert "drm/i915: Remove extra multi-gt pm-references" 2024-05-07 13:09:03 -04:00
fs Bug fixes for 6.6-rc6: 2023-10-21 09:43:09 -07:00
include drm/i915/guc: Use context hints for GT frequency 2024-03-07 10:25:06 -08:00
init workqueue: Changes for v6.6 2023-09-01 16:06:32 -07:00
io_uring io_uring: fix crash with IORING_SETUP_NO_MMAP and invalid SQ ring address 2023-10-18 09:22:14 -06:00
ipc Add x86 shadow stack support 2023-08-31 12:20:12 -07:00
kernel vmemdup-user-array API and changes with it. 2023-10-24 11:13:29 +10:00
lib maple_tree: add MAS_UNDERFLOW and MAS_OVERFLOW states 2023-09-29 17:20:46 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm: slab: Do not create kmalloc caches smaller than arch_slab_minalign() 2023-10-11 15:24:49 +02:00
net Including fixes from bluetooth, netfilter, WiFi. 2023-10-19 12:08:18 -07:00
rust rust: docs: fix logo replacement 2023-10-19 16:40:00 +02:00
samples VFIO updates for v6.6-rc1 2023-08-30 20:36:01 -07:00
scripts kbuild: remove stale code for 'source' symlink in packaging scripts 2023-10-01 23:06:06 +09:00
security KEYS: trusted: Remove redundant static calls usage 2023-10-10 11:19:43 -07:00
sound sound fixes for 6.6-rc7 2023-10-20 10:05:10 -07:00
tools Probes fixes for v6.6-rc6.2: 2023-10-21 11:00:36 -07:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt ARM: 2023-09-07 13:52:20 -07:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: rename binkernel.spec to kernel.spec 2023-07-25 00:59:33 +09:00
.mailmap MAINTAINERS: update Matthieu's email address 2023-10-05 09:34:32 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Linux 6.6-rc7 2023-10-23 18:20:06 +10:00
Makefile Linux 6.6-rc7 2023-10-22 12:11:21 -10:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.