On Tue, 2018-01-23 at 10:40 -0800, Dave Hansen wrote:
>
> I'd really rather we break this out into a nice, linear set of
> true/false conditions.
>
> bool early_cpu_vulnerable_meltdown(struct cpuinfo_x86 *c)
> {
> u64 ia32_cap = 0;
>
> /* AMD processors are not subject to Meltdown exploit: */
> if (c->x86_vendor == X86_VENDOR_AMD)
> return false;
>
> /* Assume all remaining CPUs not enumerating are vulnerable: */
> if (!cpu_has(c, X86_FEATURE_ARCH_CAPABILITIES))
> return true;
>
> /*
> * Does the CPU explicitly enumerate that it is not vulnerable
> * to Rogue Data Cache Load (aka Meltdown)?
> */
> rdmsrl(MSR_IA32_ARCH_CAPABILITIES, ia32_cap);
> if (ia32_cap & ARCH_CAP_RDCL_NO)
> return false;
>
> /* Assume everything else is vulnerable */
> return true;
> }Makes sense. It also starts to address Alan's "starting to get messy" comment, and gives a simple way to add other conditions.
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