Re: [PATCH v3 04/13] arm64: alternatives: use tpidr_el2 on VHE hosts

Catalin Marinas
2017-10-13T15:31:48Z

On Fri, Sep 22, 2017 at 07:26:05PM +0100, James Morse wrote:
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index cd52d365d1f0..8e4c7da2b126 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -865,6 +865,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
> .capability = ARM64_HAS_VIRT_HOST_EXTN,
> .def_scope = SCOPE_SYSTEM,
> .matches = runs_at_el2,
> + .enable = cpu_copy_el2regs,
> },
> {
> .desc = "32-bit EL0 Support",
> @@ -1308,3 +1309,25 @@ static int __init enable_mrs_emulation(void)
> }
>
> late_initcall(enable_mrs_emulation);
> +
> +int cpu_copy_el2regs(void *__unused)
> +{
> + int do_copyregs = 0;
> +
> + /*
> + * Copy register values that aren't redirected by hardware.
> + *
> + * Before code patching, we only set tpidr_el1, all CPUs need to copy
> + * this value to tpidr_el2 before we patch the code. Once we've done
> + * that, freshly-onlined CPUs will set tpidr_el2, so we don't need to
> + * do anything here.
> + */
> + asm volatile(ALTERNATIVE("mov %0, #1", "mov %0, #0",
> + ARM64_HAS_VIRT_HOST_EXTN)
> + : "=r" (do_copyregs) : : );

Can you just do:

if (cpu_have_const_cap(ARM64_HAS_VIRT_HOST_EXTN))
write_sysreg(read_sysreg(tpidr_el1), tpidr_el2);

At this point the capability bits should be set and the jump labels
enabled.

Otherwise:

Reviewed-by: Catalin Marinas <catalin.marinas-5wv7dgnIgG8@public.gmane.org>