This is a note to let you know that I've just added the patch titled
x86/fpu: Set X86_FEATURE_OSXSAVE feature after enabling OSXSAVE in CR4
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-fpu-set-x86_feature_osxsave-feature-after-enabling-osxsave-in-cr4.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 2c66ca3949dc701da7f4c9407f2140ae425683a5 Mon Sep 17 00:00:00 2001
From: Feng Tang <feng.tang@xxxxxxxxx>
Date: Wed, 23 Aug 2023 14:57:47 +0800
Subject: x86/fpu: Set X86_FEATURE_OSXSAVE feature after enabling OSXSAVE in CR4
From: Feng Tang <feng.tang@xxxxxxxxx>
commit 2c66ca3949dc701da7f4c9407f2140ae425683a5 upstream.
0-Day found a 34.6% regression in stress-ng's 'af-alg' test case, and
bisected it to commit b81fac906a8f ("x86/fpu: Move FPU initialization into
arch_cpu_finalize_init()"), which optimizes the FPU init order, and moves
the CR4_OSXSAVE enabling into a later place:
arch_cpu_finalize_init
identify_boot_cpu
identify_cpu
generic_identify
get_cpu_cap --> setup cpu capability
...
fpu__init_cpu
fpu__init_cpu_xstate
cr4_set_bits(X86_CR4_OSXSAVE);
As the FPU is not yet initialized the CPU capability setup fails to set
X86_FEATURE_OSXSAVE. Many security module like 'camellia_aesni_avx_x86_64'
depend on this feature and therefore fail to load, causing the regression.
Cure this by setting X86_FEATURE_OSXSAVE feature right after OSXSAVE
enabling.
[ tglx: Moved it into the actual BSP FPU initialization code and added a comment ]
Fixes: b81fac906a8f ("x86/fpu: Move FPU initialization into arch_cpu_finalize_init()")
Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/lkml/202307192135.203ac24e-oliver.sang@xxxxxxxxx
Link: https://lore.kernel.org/lkml/20230823065747.92257-1-feng.tang@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/fpu/xstate.c | 7 +++++++
1 file changed, 7 insertions(+)
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -809,6 +809,13 @@ void __init fpu__init_system_xstate(void
goto out_disable;
}
+ /*
+ * CPU capabilities initialization runs before FPU init. So
+ * X86_FEATURE_OSXSAVE is not set. Now that XSAVE is completely
+ * functional, set the feature bit so depending code works.
+ */
+ setup_force_cpu_cap(X86_FEATURE_OSXSAVE);
+
print_xstate_offset_size();
pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is %d bytes, using '%s' format.\n",
xfeatures_mask_all,
Patches currently in stable-queue which might be from feng.tang@xxxxxxxxx are
queue-5.15/x86-fpu-set-x86_feature_osxsave-feature-after-enabling-osxsave-in-cr4.patch
