The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: 2c66ca3949dc701da7f4c9407f2140ae425683a5 Gitweb: https://git.kernel.org/tip/2c66ca3949dc701da7f4c9407f2140ae425683a5 Author: Feng Tang feng.tang@intel.com AuthorDate: Wed, 23 Aug 2023 14:57:47 +08:00 Committer: Thomas Gleixner tglx@linutronix.de CommitterDate: Thu, 24 Aug 2023 11:01:45 +02:00
x86/fpu: Set X86_FEATURE_OSXSAVE feature after enabling OSXSAVE in CR4
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@intel.com Signed-off-by: Feng Tang feng.tang@intel.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: stable@vger.kernel.org Link: https://lore.kernel.org/lkml/202307192135.203ac24e-oliver.sang@intel.com Link: https://lore.kernel.org/lkml/20230823065747.92257-1-feng.tang@intel.com --- arch/x86/kernel/fpu/xstate.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 0bab497..1afbc48 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -882,6 +882,13 @@ void __init fpu__init_system_xstate(unsigned int legacy_size) 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", fpu_kernel_cfg.max_features,