On Fri, May 11, 2018 at 11:38:06AM +0100, Andrew Cooper wrote:
> At the moment, we have two different encodings of Xen's MSR_SPEC_CTRL value,
> which is a side effect of how the Spectre series developed. One encoding is
> via an alias with the bottom bit of bti_ist_info, and can encode IBRS or not,
> but not other configuraitons such as STIBP.
>
> Break Xen's value out into a separate variable (in the top of stack block for
> XPTI reasons) and use this instead of bti_ist_info in the IST path.
>
> Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
Reviewed-by: Wei Liu <wei.l...@citrix.com>
>
> /*
> @@ -417,8 +421,6 @@ void __init init_speculation_mitigations(void)
>
> static void __init __maybe_unused build_assertions(void)
> {
> - /* The optimised assembly relies on this alias. */
> - BUILD_BUG_ON(BTI_IST_IBRS != SPEC_CTRL_IBRS);
I was about to suggest removing this function entirely but it is in fact
filled in later, so this is fine.
Wei.
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