Re: [PATCH] arm64: KVM: Invoke compute_layout() before alternatives are applied
From: James Morse <james.morse@arm.com>
Date: 2019-10-17 17:42:01
Also in:
kvmarm
Hi Sebastian, On 16/10/2019 17:59, Sebastian Andrzej Siewior wrote:
compute_layout() is invoked as part of an alternative fixup under stop_machine(). This function invokes get_random_long() which acquires a sleeping lock on -RT which can not be acquired in this context.
Rename compute_layout() to kvm_compute_layout() and invoke it before stop_machines() invokes the fixups.
Nit: stop_machine() applies the alternatives.
Add a __init prefix to kvm_compute_layout() because the caller has it, too (and so the code can be discarded after boot).
quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h index b9f8d787eea9f..7532f044d713b 100644 --- a/arch/arm64/include/asm/alternative.h +++ b/arch/arm64/include/asm/alternative.h@@ -35,6 +35,12 @@ void apply_alternatives_module(void *start, size_t length); static inline void apply_alternatives_module(void *start, size_t length) { } #endif +#ifdef CONFIG_KVM_ARM_HOST +void kvm_compute_layout(void); +#else +static inline void kvm_compute_layout(void) { } +#endif
I don't think alternative.h is where this belongs... Could you move it to kvm_mmu.h, which is where the kvm_update_va_mask macro that depends on it lives. You can avoid the #ifdef if you use if(IS_ENABLED()) in the caller. This has the advantage that the compiler will catch invalid C regardless of the build options. (and its easier on the eye)
quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c index d1757ef1b1e74..c28652ee06f64 100644 --- a/arch/arm64/kernel/alternative.c +++ b/arch/arm64/kernel/alternative.c@@ -238,6 +238,7 @@ static int __apply_alternatives_multi_stop(void *unused) void __init apply_alternatives_all(void) { /* better not try code patching on a live SMP system */ + kvm_compute_layout(); stop_machine(__apply_alternatives_multi_stop, NULL, cpu_online_mask); }
This is a funny place to do this kvm check, its not needed to apply the alternatives. apply_alternatives_all() is only called from smp_cpus_done(), immediately before it calls hyp_mode_check(), could we move it there to live with the 'started at EL2' message? (to save you battling the header-jungle: To include asm/kvm_mmu.h, you need to include linux/kvm_host.h first) We end up calling it unconditionally, but I don't think that matters, both callers do the right thing. With that: Reviewed-by: James Morse <james.morse@arm.com> Thanks, James _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel