On Wed, Feb 01, 2017 at 05:36:09PM +0000, Catalin Marinas wrote: > On Wed, Feb 01, 2017 at 04:33:58PM +0000, Will Deacon wrote: > > On Wed, Feb 01, 2017 at 11:29:22AM -0500, Christopher Covington wrote: > > > On 01/31/2017 12:56 PM, Marc Zyngier wrote: > > > > Given that all ARMv8 CPUs can support SW_PAN, it is more likely to be > > > > enabled than the ARMv8.1 PAN. I'd vote for supporting the workaround in > > > > that case too, and hope that people do enable the HW version. > > > > > > Okay, I'll do my best to add support for the SW PAN case. I rebased and > > > submitted v6 of the E1009 patch [1] so that it no longer depends on this > > > patch landing first, if you all are inclined to pick it up while work on > > > this E1003 patch continues. > > > > The alternative is not enabling SW_PAN (at runtime) if this errata is > > present, along with a warning stating that hardware-PAN should be > > enabled in kconfig instead. Not sure what distributions will make of that > > though. > > The problem with this patch is that when ARM64_SW_TTBR0_PAN is enabled > and in the absence of hardware PAN (or ARM64_PAN disabled), > cpu_do_switch_mm is no longer called for user process switching, so the > workaround is pretty much useless. Oh, I see what you mean now. > I'm ok with adding the Kconfig dependency below to > QCOM_FALKOR_ERRATUM_1003: > > depends on !ARM64_SW_TTBR0_PAN || ARM64_PAN > > together with a run-time warning if ARM64_SW_TTBR0_PAN is being used. That makes it look like hardware-PAN is the cause of the erratum. Maybe just select ARM64_PAN if the erratum workaround is selected, then runtime warning if we find that the h/w doesn't have PAN but does have the erratum (which should never fire)? Will
