Re: [Xen-devel] [PATCH v8 11/17] x86: Protect unaware domains from meddling hyperthreads

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 17/01/2018 08:40, Jan Beulich wrote:
>>>> On 16.01.18 at 22:11, <andrew.cooper3@xxxxxxxxxx> wrote:
>> An alternative to the current levelling logic would be to treat STIBP as
>> a Special Bit (in CPUID terms, like OSXSAVE/etc) and unconditionally set
>> it equal to IBRS, irrespective of the toolstack setting.  That way,
>> migration between HT and non-HT hardware is safe and a VM which chooses
>> to use STIBP will work even on non-HT hardware which simply ignores the
>> request.
> Wouldn't that overall result in simpler code anyway?

Much, except its only become an option since yesterday.

~Andrew

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