Re: [Xen-devel] [PATCH v8 01/17] x86: Support compiling with indirect branch thunks

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 14/01/2018 19:48, David Woodhouse wrote:
> On Fri, 2018-01-12 at 18:00 +0000, Andrew Cooper wrote:
>> +.macro IND_THUNK_RETPOLINE reg:req
>> +        call 2f
>> +1:
> Linux and GCC have now settled on 'pause;lfence;jmp' here.

And elsewhere.  It is probably worth taking, but it takes us to 17 bytes
which is frustratingly over one cache line.

~Andrew

>
>> +        lfence
>> +        jmp 1b
>> +2:
>> +        mov %\reg, (%rsp)
>> +        ret
>> +.endm
>> +


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