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cherry-pick fix for setting X86_FEATURE_OSXSAVE feature

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Avoids regressions where some code falsely think they cannot use some
CPU features like AVX1, e.g., ZFS.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
This commit is contained in:
Thomas Lamprecht 2023-09-19 09:27:09 +02:00
parent 61656497ef
commit 9ba0dde971
1 changed files with 61 additions and 0 deletions
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patches/kernel/0016-x86-fpu-Set-X86_FEATURE_OSXSAVE-feature-after-enabli.patch Normal file
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@ -0,0 +1,61 @@
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Feng Tang <feng.tang@intel.com>
Date: Wed, 23 Aug 2023 14:57:47 +0800
Subject: [PATCH] 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
(cherry picked from commit 2c66ca3949dc701da7f4c9407f2140ae425683a5)
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.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 0bab497c9436..1afbc4866b10 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,