[v2] kvm/ppc: IRQ disabling cleanup

Simplify the handling of lazy EE by going directly from fully-enabled
to hard-disabled.  This replaces the lazy_irq_pending() check
(including its misplaced kvm_guest_exit() call).

As suggested by Tiejun Chen, move the interrupt disabling into
kvmppc_prepare_to_enter() rather than have each caller do it.  Also
move the IRQ enabling on heavyweight exit into
kvmppc_prepare_to_enter().

Signed-off-by: Scott Wood <scottwood@freescale.com>
---
v2:
 - rebased
 - removed redundant (on 64-bit) and possibly performance-affecting WARNs
 - addressed cosmetic feedback

 arch/powerpc/include/asm/kvm_ppc.h |  6 ++++++
 arch/powerpc/kvm/book3s_pr.c       | 14 ++++++--------
 arch/powerpc/kvm/booke.c           | 12 +++++-------
 arch/powerpc/kvm/powerpc.c         | 26 +++++++++-----------------
 4 files changed, 26 insertions(+), 32 deletions(-)

On 10.01.2014, at 02:18, Scott Wood <scottwood@freescale.com> wrote:

> Simplify the handling of lazy EE by going directly from fully-enabled
> to hard-disabled.  This replaces the lazy_irq_pending() check
> (including its misplaced kvm_guest_exit() call).
> 
> As suggested by Tiejun Chen, move the interrupt disabling into
> kvmppc_prepare_to_enter() rather than have each caller do it.  Also
> move the IRQ enabling on heavyweight exit into
> kvmppc_prepare_to_enter().
> 
> Signed-off-by: Scott Wood <scottwood@freescale.com>

Thanks, applied to kvm-ppc-queue.


Alex

> ---
> v2:
> - rebased
> - removed redundant (on 64-bit) and possibly performance-affecting WARNs
> - addressed cosmetic feedback
> 
> arch/powerpc/include/asm/kvm_ppc.h |  6 ++++++
> arch/powerpc/kvm/book3s_pr.c       | 14 ++++++--------
> arch/powerpc/kvm/booke.c           | 12 +++++-------
> arch/powerpc/kvm/powerpc.c         | 26 +++++++++-----------------
> 4 files changed, 26 insertions(+), 32 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
> index c8317fb..e64881cd 100644
> --- a/arch/powerpc/include/asm/kvm_ppc.h
> +++ b/arch/powerpc/include/asm/kvm_ppc.h
> @@ -455,6 +455,12 @@ static inline void kvmppc_fix_ee_before_entry(void)
> 	trace_hardirqs_on();
> 
> #ifdef CONFIG_PPC64
> +	/*
> +	 * To avoid races, the caller must have gone directly from having
> +	 * interrupts fully-enabled to hard-disabled.
> +	 */
> +	WARN_ON(local_paca->irq_happened != PACA_IRQ_HARD_DIS);
> +
> 	/* Only need to enable IRQs by hard enabling them after this */
> 	local_paca->irq_happened = 0;
> 	local_paca->soft_enabled = 1;
> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
> index fe14ca3..ce7accc 100644
> --- a/arch/powerpc/kvm/book3s_pr.c
> +++ b/arch/powerpc/kvm/book3s_pr.c
> @@ -1023,14 +1023,14 @@ program_interrupt:
> 		 * and if we really did time things so badly, then we just exit
> 		 * again due to a host external interrupt.
> 		 */
> -		local_irq_disable();
> 		s = kvmppc_prepare_to_enter(vcpu);
> -		if (s <= 0) {
> -			local_irq_enable();
> +		if (s <= 0)
> 			r = s;
> -		} else {
> +		else {
> +			/* interrupts now hard-disabled */
> 			kvmppc_fix_ee_before_entry();
> 		}
> +
> 		kvmppc_handle_lost_ext(vcpu);
> 	}
> 
> @@ -1277,12 +1277,10 @@ static int kvmppc_vcpu_run_pr(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
> 	 * really did time things so badly, then we just exit again due to
> 	 * a host external interrupt.
> 	 */
> -	local_irq_disable();
> 	ret = kvmppc_prepare_to_enter(vcpu);
> -	if (ret <= 0) {
> -		local_irq_enable();
> +	if (ret <= 0)
> 		goto out;
> -	}
> +	/* interrupts now hard-disabled */
> 
> 	/* Save FPU state in stack */
> 	if (current->thread.regs->msr & MSR_FP)
> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> index 53e65a2..626b431 100644
> --- a/arch/powerpc/kvm/booke.c
> +++ b/arch/powerpc/kvm/booke.c
> @@ -643,7 +643,7 @@ int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
> 		local_irq_enable();
> 		kvm_vcpu_block(vcpu);
> 		clear_bit(KVM_REQ_UNHALT, &vcpu->requests);
> -		local_irq_disable();
> +		hard_irq_disable();
> 
> 		kvmppc_set_exit_type(vcpu, EMULATED_MTMSRWE_EXITS);
> 		r = 1;
> @@ -692,13 +692,12 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
> 		return -EINVAL;
> 	}
> 
> -	local_irq_disable();
> 	s = kvmppc_prepare_to_enter(vcpu);
> 	if (s <= 0) {
> -		local_irq_enable();
> 		ret = s;
> 		goto out;
> 	}
> +	/* interrupts now hard-disabled */
> 
> #ifdef CONFIG_PPC_FPU
> 	/* Save userspace FPU state in stack */
> @@ -1217,12 +1216,11 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
> 	 * aren't already exiting to userspace for some other reason.
> 	 */
> 	if (!(r & RESUME_HOST)) {
> -		local_irq_disable();
> 		s = kvmppc_prepare_to_enter(vcpu);
> -		if (s <= 0) {
> -			local_irq_enable();
> +		if (s <= 0)
> 			r = (s << 2) | RESUME_HOST | (r & RESUME_FLAG_NV);
> -		} else {
> +		else {
> +			/* interrupts now hard-disabled */
> 			kvmppc_fix_ee_before_entry();
> 		}
> 	}
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 9ae9768..ea65029 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -68,14 +68,16 @@ int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
>  */
> int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
> {
> -	int r = 1;
> +	int r;
> +
> +	WARN_ON(irqs_disabled());
> +	hard_irq_disable();
> 
> -	WARN_ON_ONCE(!irqs_disabled());
> 	while (true) {
> 		if (need_resched()) {
> 			local_irq_enable();
> 			cond_resched();
> -			local_irq_disable();
> +			hard_irq_disable();
> 			continue;
> 		}
> 
> @@ -101,7 +103,7 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
> 			local_irq_enable();
> 			trace_kvm_check_requests(vcpu);
> 			r = kvmppc_core_check_requests(vcpu);
> -			local_irq_disable();
> +			hard_irq_disable();
> 			if (r > 0)
> 				continue;
> 			break;
> @@ -113,22 +115,12 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
> 			continue;
> 		}
> 
> -#ifdef CONFIG_PPC64
> -		/* lazy EE magic */
> -		hard_irq_disable();
> -		if (lazy_irq_pending()) {
> -			/* Got an interrupt in between, try again */
> -			local_irq_enable();
> -			local_irq_disable();
> -			kvm_guest_exit();
> -			continue;
> -		}
> -#endif
> -
> 		kvm_guest_enter();
> -		break;
> +		return 1;
> 	}
> 
> +	/* return to host */
> +	local_irq_enable();
> 	return r;
> }
> EXPORT_SYMBOL_GPL(kvmppc_prepare_to_enter);
> -- 
> 1.8.3.2
> 

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