To my knowledge, mesa has historically requested that the kernel have CONFIG_CHECKPOINT_RESTORE enabled because some mesa functions depend on the sys_kcmp system call. Traditionally, the only way to enable that syscall in Linux was to enable CONFIG_CHECKPOINT_RESTORE. However, since Linux v5.10.20 and v5.11.3, a new CONFIG_KCMP has been added to Linux to allow enabling sys_kcmp without having to enable CONFIG_CHECKPOINT_RESTORE (which enables a bunch of other usually unnecessary things otherwise not related to sys_kcmp). When I emerged mesa-libs/mesa-20.3.4, on a system running Linux v5.11.5 with CONFIG_KCMP enabled, the mesa ebuild reported this: * Messages for package media-libs/mesa-20.3.4: * CONFIG_CHECKPOINT_RESTORE: is not set when it should be. * Please check to make sure these options are set correctly. * Failure to do so may cause unexpected problems. >>> Auto-cleaning packages... Since I have CONFIG_KCMP enabled, mesa will get sys_kcmp and does not need CONFIG_CHECKPOINT_RESTORE enabled. I suggest that the mesa ebuild should first check if CONFIG_KCMP is enabled (which it only can be on the newer kernels that support it), and recommend enabling CONFIG_KCMP if the config specifically says that CONFIG_KCMP is not set (which should only be found in configs for newer kernels), otherwise recommend enabling CONFIG_CHECKPOINT_RESTORE (for the older kernels that don't have CONFIG_KCMP).
Here is the commit that introduced the change, creating a separate CONFIG_KCMP, in the linux-5.10.y branch: commit 1ea36020950d44ef9152d832887a0c1cee0edee2 Author: Chris Wilson <chris@chris-wilson.co.uk> Date: Fri Feb 5 22:00:12 2021 +0000 kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE commit bfe3911a91047557eb0e620f95a370aee6a248c7 upstream. Userspace has discovered the functionality offered by SYS_kcmp and has started to depend upon it. In particular, Mesa uses SYS_kcmp for os_same_file_description() in order to identify when two fd (e.g. device or dmabuf) point to the same struct file. Since they depend on it for core functionality, lift SYS_kcmp out of the non-default CONFIG_CHECKPOINT_RESTORE into the selectable syscall category. Rasmus Villemoes also pointed out that systemd uses SYS_kcmp to deduplicate the per-service file descriptor store. Note that some distributions such as Ubuntu are already enabling CHECKPOINT_RESTORE in their configs and so, by extension, SYS_kcmp. References: https://gitlab.freedesktop.org/drm/intel/-/issues/3046 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Kees Cook <keescook@chromium.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Will Drewry <wad@chromium.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Dave Airlie <airlied@gmail.com> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Lucas Stach <l.stach@pengutronix.de> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Cyrill Gorcunov <gorcunov@gmail.com> Cc: stable@vger.kernel.org Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> # DRM depends on kcmp Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> # systemd uses kcmp Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Thomas Zimmermann <tzimmermann@suse.de> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/20210205220012.1983-1-chris@chris-wilson.co.uk Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Thanks... So I found that the commit is in v5.12-rc1, v5.11.3, and v5.10.20. Irritating amount of logic to handle that. I hope it doesn't get backported further.
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=de371306554b093d175fa9e12163b2e377d17762 commit de371306554b093d175fa9e12163b2e377d17762 Author: Matt Turner <mattst88@gentoo.org> AuthorDate: 2021-03-11 16:36:22 +0000 Commit: Matt Turner <mattst88@gentoo.org> CommitDate: 2021-03-11 16:38:00 +0000 media-libs/mesa: Check for CONFIG_KCMP on appropriate kernel versions Closes: https://bugs.gentoo.org/775095 Signed-off-by: Matt Turner <mattst88@gentoo.org> media-libs/mesa/mesa-20.3.4.ebuild | 10 +++++++++- media-libs/mesa/mesa-21.0.0_rc5.ebuild | 12 ++++++++++-- media-libs/mesa/mesa-9999.ebuild | 12 ++++++++++-- 3 files changed, 29 insertions(+), 5 deletions(-)
