Messages in this thread | | | Date | Sat, 20 Jan 2018 21:08:11 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH 4/4] x86/pti: Do not enable PTI on fixed Intel processors |
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On Sat, 20 Jan 2018, David Woodhouse wrote:
> When they advertise the IA32_ARCH_CAPABILITIES MSR and it has the RDCL_NO > bit set, they don't need KPTI either.
Do they exist today? And do we have documentation for that new MSR already?
Thanks,
tglx
> Signed-off-by: David Woodhouse <dwmw@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 > >
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