[MODERATED] Re: [PATCH v7 04/10] TAAv7 4

On Tue, Oct 22, 2019 at 10:25:27PM -0700, speck for Pawan Gupta wrote:
> I think we first need to agree on whether disabling TSX is the
> mitigation for X86_BUG_TAA or the lack of bug. Your clearing the bug bit
> here makes me think that you are treating it as lack of bug. This series
> treats it as a mitigation when the hardware has the bug. Let me know
> your thoughts on this.

Ok, I see your point. And yes, let's do what you're suggesting because
that mirrors reality optimally:

static void __init taa_select_mitigation(void)
{ 
        u64 ia32_cap;

        if (!boot_cpu_has_bug(X86_BUG_TAA) || cpu_mitigations_off()) {
                taa_mitigation = TAA_MITIGATION_OFF;
                return;
        }

	if (!boot_cpu_has(X86_FEATURE_RTM)) {
                taa_mitigation = TAA_MITIGATION_TSX_DISABLE;
                goto out;
        }

	...

so the bug presence would take precedence and in the !X86_BUG_TAA case
or when we've disabled all mitigations, we won't say anything.

Then, if the bug is present but we've disabled TSX, we say "Mitigation:
TSX disabled".

Hohumm, makes sense to me.

Thx.

-- 
Regards/Gruss,
    Boris.

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