On Sep 18, 2014 5:13 PM, "Henrique de Moraes Holschuh" <h...@hmh.eng.br> wrote: > > On Thu, 18 Sep 2014, Henrique de Moraes Holschuh wrote: > > On Thu, 18 Sep 2014, H. Peter Anvin wrote: > > > We should, but this is also part of why we want the early ucode > > > capability. > > > > Well, yes. But that won't help the several stable and LTS distros with > > kernels without early ucode update support. > > Here's a plan that might work, pending actually checking the libpthread TSX > code to make sure it keys on /proc/cpuinfo flags:
Surely it checks cpuid directly, though. Can we twiddle the cpuid bit? I never noticed any way in the docs to do it, but if BIOS has such an ability, maybe we do, too. I wonder if there's anything semi-documented in biosbits, or if we could just reverse-engineer it. --Andy > > Add a cpu quirk, triggered by the Haswell cpuids, to force-disable hle on > the affected processors. > > This will work around the x86_capability capability issue (which should > still be fixed, anyway), and it should also get userspace to stay away from > TSX, therefore also working around the worst issue (processes getting > SIGILL). > > This will disable the "user may ask the BIOS to keep TSX enabled" > anti-feature, though. This drawback can be avoided, but only if a future > microcode update won't re-disable hle when the BIOS enabled it. For now, I > suggest that we decree that "hle is toast" for the current Haswells and add > back ways to enable it for testing when we know more about it. > > -- > "One disk to rule them all, One disk to find them. One disk to bring > them all and in the darkness grind them. In the Land of Redmond > where the shadows lie." -- The Silicon Valley Tarot > Henrique Holschuh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
