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 <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
>
>
