Messages in this thread | | | Date | Wed, 4 Oct 2017 12:10:40 +0100 | From | Catalin Marinas <> | Subject | Re: [PATCH] arm64: Enable MRS emulation early |
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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. That said, making it core_initcall() is probably not a bad thing (just a statement that it is concerned with the core initialisation), as long as all the other infrastructure it registers with is up.
For Suzuki's patch, I was thinking of enabling emulation before we register the HWCAP_CPUID bit (setup_elf_hwcaps). However, that means we have to bring it before smp_cpus_done(). It's not really worth it as we don't expect any user space at that point.
-- Catalin
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