Re: [PATCH 2/3] arm/arm64: speed up spinlocks and atomic ops

[Paolo Bonzini <pbonzini@redhat.com>]

On 25/06/2015 18:12, Andrew Jones wrote:
> spinlock torture tests made it clear that checking mmu_enabled()
> every time we call spin_lock is a bad idea. As most tests will
> want the MMU enabled the entire time, then just hard code
> mmu_enabled() to true. Tests that want to play with the MMU can
> be compiled with CONFIG_MAY_DISABLE_MMU to get the actual check
> back.

This doesn't work if you compile mmu.o just once.  Can you make
something like

static inline bool mmu_enabled(void)
{
	return disabled_mmu_cpu_count == 0 || __mmu_enabled();
}

...

bool __mmu_enabled(void)
{
	struct thread_info *ti = current_thread_info();
	return cpumask_test_cpu(ti->cpu, &mmu_enabled_cpumask);
}

?

Paolo