[PATCHv8 16/17] x86/cpu: Enable LASS during CPU initialization
From: Kirill A. Shutemov <hidden>
Date: 2025-07-01 09:59:35
Also in:
linux-efi, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
From: Sohil Mehta <redacted> Being a security feature, enable LASS by default if the platform supports it. While at it, get rid of the comment above the SMAP/SMEP/UMIP/LASS setup instead of updating it to mention LASS as well, as the whole sequence is quite self-explanatory. Signed-off-by: Sohil Mehta <redacted> Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: Kirill A. Shutemov <redacted> --- arch/x86/kernel/cpu/common.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 1552c7510380..97a228f917a9 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c@@ -401,6 +401,12 @@ static __always_inline void setup_umip(struct cpuinfo_x86 *c) cr4_clear_bits(X86_CR4_UMIP); } +static __always_inline void setup_lass(struct cpuinfo_x86 *c) +{ + if (cpu_feature_enabled(X86_FEATURE_LASS)) + cr4_set_bits(X86_CR4_LASS); +} + /* These bits should not change their value after CPU init is finished. */ static const unsigned long cr4_pinned_mask = X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP | X86_CR4_FSGSBASE | X86_CR4_CET | X86_CR4_FRED |
@@ -1975,10 +1981,10 @@ static void identify_cpu(struct cpuinfo_x86 *c) /* Disable the PN if appropriate */ squash_the_stupid_serial_number(c); - /* Set up SMEP/SMAP/UMIP */ setup_smep(c); setup_smap(c); setup_umip(c); + setup_lass(c); /* Enable FSGSBASE instructions if available. */ if (cpu_has(c, X86_FEATURE_FSGSBASE)) {
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2.47.2