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Janusz Krzysztofik 647535760a 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>
(cherry picked from commit 749670a58d)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
2024-05-29 11:35:08 +03:00
arch 16 hotfixes, 11 of which are cc:stable. 2024-05-25 15:10:33 -07:00
block block-6.10-20240523 2024-05-23 13:44:47 -07:00
certs kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
crypto This push fixes a bug in the new ecc P521 code as well as a buggy 2024-05-20 08:47:54 -07:00
Documentation 16 hotfixes, 11 of which are cc:stable. 2024-05-25 15:10:33 -07:00
drivers Revert "drm/i915: Remove extra multi-gt pm-references" 2024-05-29 11:35:08 +03:00
fs four smb client fixes, including two important netfs integration fixes 2024-05-25 22:33:10 -07:00
include mm: percpu: Include smp.h in alloc_tag.h 2024-05-26 14:40:39 -07:00
init Driver core changes for 6.10-rc1 2024-05-22 12:13:40 -07:00
io_uring io_uring-6.10-20240523 2024-05-23 13:41:49 -07:00
ipc Mainly singleton patches, documented in their respective changelogs. 2024-05-19 14:02:03 -07:00
kernel Misc fixes: 2024-05-25 14:48:40 -07:00
lib 16 hotfixes, 11 of which are cc:stable. 2024-05-25 15:10:33 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm 16 hotfixes, 11 of which are cc:stable. 2024-05-25 15:10:33 -07:00
net NFS client updates for Linux 6.10 2024-05-23 13:51:09 -07:00
rust LoongArch changes for v6.10 2024-05-22 09:43:07 -07:00
samples tracing/treewide: Remove second parameter of __assign_str() 2024-05-22 20:14:47 -04:00
scripts - A series ("kbuild: enable more warnings by default") from Arnd 2024-05-22 18:59:29 -07:00
security hardening fixes for v6.10-rc1 2024-05-24 08:33:44 -07:00
sound sound fixes for 6.10-rc1 2024-05-24 08:48:51 -07:00
tools Revert a patch causing a regression as described in the cset: 2024-05-26 09:54:26 -07:00
usr kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
virt The usual shower of singleton fixes and minor series all over MM, 2024-05-19 09:21:03 -07:00
.clang-format clang-format: Update with v6.7-rc4's for_each macro list 2023-12-08 23:54:38 +01:00
.cocciconfig
.editorconfig Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: create a list of all built DTB files 2024-02-19 18:20:39 +09:00
.mailmap mailmap: update email address for Satya Priya 2024-05-24 11:55:05 -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 MAINTAINERS: Drop Gustavo Pimentel as PCI DWC Maintainer 2024-03-27 13:41:02 -05:00
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 RTC for 6.10 2024-05-25 13:33:53 -07:00
Makefile Linux 6.10-rc1 2024-05-26 15:20:12 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.