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| author | Eric Biggers <ebiggers@kernel.org> | 2026-09-01 07:57:33 -0700 |
|---|---|---|
| committer | Borislav Petkov (AMD) <bp@alien8.de> | 2026-09-02 10:35:40 -0700 |
| commit | 518aa9948e4f2ba69b7066371d3ac8e4d31d604e (patch) | |
| tree | 1e01fb040b6a3c1ebf866814e7ab921461e33b7c /arch/x86/kernel | |
| parent | cee9395acd8043be0644b25c34bfa86623f2b935 (diff) | |
| download | linux-next-518aa9948e4f2ba69b7066371d3ac8e4d31d604e.tar.gz linux-next-518aa9948e4f2ba69b7066371d3ac8e4d31d604e.zip | |
x86/fpu: Check for missing AVX and AVX-512 xstate bits
If the CPU declares AVX or AVX-512 support, verify that the corresponding
xstate bits are also set. If not, warn and clear them.
This eliminates the perceived need for AVX and AVX-512 optimized code in the
kernel to call cpu_has_xfeatures(). That has never been universally done,
which strongly suggests that it has never really been needed in practice, but
this should remove any remaining doubt.
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Christoph Hellwig <hch@lst.de>
Link: https://patch.msgid.link/20260901145740.42337-2-ebiggers@kernel.org
Diffstat (limited to 'arch/x86/kernel')
| -rw-r--r-- | arch/x86/kernel/fpu/xstate.c | 25 |
1 files changed, 23 insertions, 2 deletions
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index a7b6524a9dea..97cfd4fb6cc0 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -806,7 +806,7 @@ static u64 __init guest_default_mask(void) void __init fpu__init_system_xstate(unsigned int legacy_size) { unsigned int eax, ebx, ecx, edx; - u64 xfeatures; + u64 xfeatures, mask; int err; int i; @@ -818,6 +818,8 @@ void __init fpu__init_system_xstate(unsigned int legacy_size) if (!boot_cpu_has(X86_FEATURE_XSAVE)) { pr_info("x86/fpu: x87 FPU will use %s\n", boot_cpu_has(X86_FEATURE_FXSR) ? "FXSAVE" : "FSAVE"); + /* Disable all dependent flags too */ + setup_clear_cpu_cap(X86_FEATURE_XSAVE); return; } @@ -833,7 +835,8 @@ void __init fpu__init_system_xstate(unsigned int legacy_size) cpuid_count(CPUID_LEAF_XSTATE, 1, &eax, &ebx, &ecx, &edx); fpu_kernel_cfg.max_features |= ecx + ((u64)edx << 32); - if ((fpu_kernel_cfg.max_features & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) { + mask = XFEATURE_MASK_FPSSE; + if ((fpu_kernel_cfg.max_features & mask) != mask) { /* * This indicates that something really unexpected happened * with the enumeration. Disable XSAVE and try to continue @@ -844,6 +847,24 @@ void __init fpu__init_system_xstate(unsigned int legacy_size) goto out_disable; } + mask |= XFEATURE_MASK_YMM; + if (boot_cpu_has(X86_FEATURE_AVX)) { + if ((fpu_kernel_cfg.max_features & mask) != mask) { + pr_err(FW_BUG + "x86/fpu: Disabling AVX support due to missing xstate features\n"); + setup_clear_cpu_cap(X86_FEATURE_AVX); + } + } + + mask |= XFEATURE_MASK_AVX512; + if (boot_cpu_has(X86_FEATURE_AVX512F)) { + if ((fpu_kernel_cfg.max_features & mask) != mask) { + pr_err(FW_BUG + "x86/fpu: Disabling AVX-512 support due to missing xstate features\n"); + setup_clear_cpu_cap(X86_FEATURE_AVX512F); + } + } + if (fpu_kernel_cfg.max_features & XFEATURE_MASK_APX && fpu_kernel_cfg.max_features & (XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR)) { /* |