Request for testers: glibc update to work around Intel TSX errata microcode_ctl problems.

[Reindl Harald]

Am 29.09.2014 um 00:21 schrieb Andrew Lutomirski:
> On Sep 28, 2014 12:25 PM, "Reindl Harald" <h.reindl at thelounge.net <mailto:h.reindl at thelounge.net>> wrote:
>>
>> Am 28.09.2014 um 21:15 schrieb drago01:
>> > On Sun, Sep 28, 2014 at 8:17 PM, Reindl Harald <h.reindl at thelounge.net <mailto:h.reindl at thelounge.net>> wrote:
>> >>
>> >> Am 28.09.2014 um 20:13 schrieb Carlos O'Donell:
>> >>> On 09/28/2014 01:24 PM, drago01 wrote:
>> >>>> On Sun, Sep 28, 2014 at 6:49 PM, Carlos O'Donell <carlos at redhat.com <mailto:carlos at redhat.com>> wrote:
>> >>>> Does that update still make sense given that the kernel / dracut
>> >>>> update enables early microcode loading?
>> >>>
>> >>> What about the case where the user runs a custom kernel?
>> >>
>> >> then he needs to build it right
>> >>
>> >> don't get me wrong but you can't seriously disable TSX
>> >> completly because a *possible* out-of-distribution kernel
>> >
>> > Well the microcode update *does* disable TSX (so that only applies to
>> > new yet to be introduced cpus) ...
>>
>> that's the point of what i said:
>>
>> * you buy a new CPU in 2 months
>> * the microcode don't disable TSX there
> 
> What hypothetical CPU is this?  I don't think Broadwell has TSX

TSX was introduced with Haswell
otherwise the thread and the microcode to disable it now would not exist

http://www.anandtech.com/show/8376/intel-disables-tsx-instructions-erratum-found-in-haswell-haswelleep-broadwelly

> so I think we're talking about Skylake here

see above - who other than Intel knows if the next Haswell/Broadwell
becomes a new "Step" with fixes and enables TSX again but only for
the newer ones

however - how does that matter?

you can either build all without TSX forever or load microcode
early enough that it is masked controlled by the microcode
before it is used while apply the microcode later disables
the instructions which is the current topic

>> * if glibc now is built without TSX support you gain nothing from new hardware
>> * if kernel loads microcode early and you have hardware supporting
>>   TSX and glibc also supports it -> fine you hav ethe feature
>>
>> it would be a big mistake to disable completly TSX forever and
>> if not forever how would someone decide when enable it - the only
>> sane way is to get microcode applid as early as possible and
>> after that use the CPU feautures which are enabled
>>
>> > but yeah if you build your own kernel you should try to be
>> > as close to possible to the distro config
>>
>> exactly what i said

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 181 bytes
Desc: OpenPGP digital signature
URL: <http://lists.fedoraproject.org/pipermail/devel/attachments/20140929/3c24c832/attachment.sig>