Am 29.09.2014 um 00:21 schrieb Andrew Lutomirski: > On Sep 28, 2014 12:25 PM, "Reindl Harald" <h.reindl@xxxxxxxxxxxxx <mailto:h.reindl@xxxxxxxxxxxxx>> wrote: >> >> Am 28.09.2014 um 21:15 schrieb drago01: >> > On Sun, Sep 28, 2014 at 8:17 PM, Reindl Harald <h.reindl@xxxxxxxxxxxxx <mailto:h.reindl@xxxxxxxxxxxxx>> 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@xxxxxxxxxx <mailto:carlos@xxxxxxxxxx>> 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
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