Messages in this thread | | | Subject | Re: [PATCH] arm64: Enable MRS emulation early | From | Suzuki K Poulose <> | Date | Wed, 4 Oct 2017 14:00:35 +0100 |
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On 04/10/17 12:32, Mark Rutland wrote: > On Wed, Oct 04, 2017 at 12:10:40PM +0100, Catalin Marinas wrote: >> On Wed, Oct 04, 2017 at 11:14:26AM +0100, Mark Rutland wrote: >>> On Wed, Oct 04, 2017 at 10:48:05AM +0100, Suzuki K Poulose wrote: >>>> Make sure the MRS emulation is enabled early enough, such that the >>>> early userspace applications (e.g, those run from initrd) could >>>> use the facility without crashing them. >>>> >>>> Fixes: commit 77c97b4ee2129 ("arm64: cpufeature: Expose CPUID registers by emulation") >>>> Reported-by: Matwey V. Kornilov <matwey.kornilov@gmail.com> >>>> Cc: James Morse <james.morse@arm.com> >>>> Cc: Dave Martin <Dave.martin@arm.com> >>>> Cc: Catalin Marinas <catalin.marinas@arm.com> >>>> Cc: Will Deacon <will.deacon@arm.com> >>>> Cc: stable@vger.kernel.org >>>> Cc: Mark Rutland <mark.rutland@arm.com> >>>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> >>> >>> This looks sensible, but shouldn't we do the same for other >>> late_inicalls can affect initrd userspace? >>> >>> e.g. armv8_deprecated_init, fpsimd_init, sys_reg_genericv8_init? >> >> I think we should, though not all of them are concerned with the user >> code. For example, fpsimd_init() takes care of the pm/hotplug aspect and >> nothing to do with user space. > > My worry was that without the pm/hotplug notifiers, things could go > wrong during the initrd. e.g. we could lose userspace fp state without > the pm notifier, or userspace could trigger hotplpug that we wouldn't > manage correctly > > So even if it's not directly userspace related, it can affect (or can be > affected by) initrd userspace.
You're right. In fact, I had a version of the patch which enables the emulation as soon as we have initialised the ELF_HWCAPs from setup_cpu_features(), rather than depending on an initcall. But that requires moving the setup_cpu_features() to the bottom, which makes the hunk look a bit more complex than it is.
And similarly, we should be able to do the fpsimd_init from setup_cpu_features(), as we have finalised the HWCAPs and pm_register_notifier any adds the entry to a static list of notifiers ( even though the cpu_pm callbacks are registered as a core_initcall() ).
Similarly for sys_reg_genericv8_init & armv8_deprecated_init could be made a core initcall.
I think it would be good to separate them out.
i.e, enable_mrs_emulation & fpsimd_init from setup_cpu_features() and the other two promoted as core_initcalls.
Thoughts ?
Suzuki
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