When they advertise the IA32_ARCH_CAPABILITIES MSR and it has the RDCL_NO bit set, they don't need KPTI either.
Signed-off-by: David Woodhouse <d...@amazon.co.uk> --- arch/x86/kernel/cpu/common.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index e5d66e9..80572ae 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -900,8 +900,13 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) setup_force_cpu_cap(X86_FEATURE_ALWAYS); - if (c->x86_vendor != X86_VENDOR_AMD) - setup_force_cpu_bug(X86_BUG_CPU_MELTDOWN); + if (c->x86_vendor != X86_VENDOR_AMD) { + unsigned long ia32_cap = 0; + if (cpu_has(c, X86_FEATURE_ARCH_CAPABILITIES)) + rdmsrl(MSR_IA32_ARCH_CAPABILITIES, ia32_cap); + if (!(ia32_cap & ARCH_CAP_RDCL_NO)) + setup_force_cpu_bug(X86_BUG_CPU_MELTDOWN); + } setup_force_cpu_bug(X86_BUG_SPECTRE_V1); setup_force_cpu_bug(X86_BUG_SPECTRE_V2); -- 2.7.4