Re: [PATCH 0/8] x86: Disentangle the vdso and clean it up

[Andy Lutomirski]

On Mon, Oct 20, 2014 at 2:41 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> On 09/23/2014 10:50 AM, Andy Lutomirski wrote:
>>
>> Patch 8 removes the vvar that selects the getcpu mode.  That vvar
>> has been unnecessary for a couple of years, ever since alternative
>> patching has worked in the vdso.
>>
>
> Is there any fundamental reason to not always use LSL at this point?

No, other than aesthetics.

Crappy timings on my dev box:

rdtscp: 18ns (and slowdown of nearly insns because it's like lfence or
mfence IIRC)

lsl: 15ns

just for fun, lsl of an out of bounds descriptor: 46ns

lsl is also nice because it works even if CR4.TSD is set.

I know I probably shouldn't say this, but sgdt is even faster (<8ns)

Should I send a replacement for patch 8 or should I let you merge 1-7
and fold this into the followup series?

--Andy
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