x86/fpu: Set X86_FEATURE_OSXSAVE feature after enabling OSXSAVE in CR4

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@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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 7d372db8bee1186f8a211f5839d6baae7962c5a4..e33b732ad33764eb7b995a826de417abc94d3dce 100644 (file)
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -811,6 +811,14 @@ void __init fpu__init_system_xstate(void)
        fpu__init_prepare_fx_sw_frame();
        setup_init_fpu_buf();
        setup_xstate_comp();
+
+       /*
+        * 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",