[PATCH 3/6] KVM: PPC: Book3S HV P9: Move cede logic out of XIVE escalation rearming

[Cédric Le Goater]

On 3/3/22 06:33, Nicholas Piggin wrote:
> Move the cede abort logic out of xive escalation rearming and into
> the caller to prepare for handling a similar case with nested guest
> entry.
> 
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>

Reviewed-by: Cédric Le Goater <clg at kaod.org>

In xive_esc_irq() :

	if (vcpu->arch.ceded)
		kvmppc_fast_vcpu_kick(vcpu);

which does :

	vcpu->kvm->arch.kvm_ops->fast_vcpu_kick(vcpu);


That's a lot of indirection which are costly on PPC. May be for this case,
since we know XIVE is only supported on KVM HV, we could use directly
kvmppc_fast_vcpu_kick_hv().

Thanks,

C.

> ---
>   arch/powerpc/include/asm/kvm_ppc.h |  4 ++--
>   arch/powerpc/kvm/book3s_hv.c       | 10 ++++++++--
>   arch/powerpc/kvm/book3s_xive.c     |  9 ++++++---
>   3 files changed, 16 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
> index a14dbcd1b8ce..94fa5f246657 100644
> --- a/arch/powerpc/include/asm/kvm_ppc.h
> +++ b/arch/powerpc/include/asm/kvm_ppc.h
> @@ -671,7 +671,7 @@ extern int kvmppc_xive_set_irq(struct kvm *kvm, int irq_source_id, u32 irq,
>   			       int level, bool line_status);
>   extern void kvmppc_xive_push_vcpu(struct kvm_vcpu *vcpu);
>   extern void kvmppc_xive_pull_vcpu(struct kvm_vcpu *vcpu);
> -extern void kvmppc_xive_rearm_escalation(struct kvm_vcpu *vcpu);
> +extern bool kvmppc_xive_rearm_escalation(struct kvm_vcpu *vcpu);
>   
>   static inline int kvmppc_xive_enabled(struct kvm_vcpu *vcpu)
>   {
> @@ -709,7 +709,7 @@ static inline int kvmppc_xive_set_irq(struct kvm *kvm, int irq_source_id, u32 ir
>   				      int level, bool line_status) { return -ENODEV; }
>   static inline void kvmppc_xive_push_vcpu(struct kvm_vcpu *vcpu) { }
>   static inline void kvmppc_xive_pull_vcpu(struct kvm_vcpu *vcpu) { }
> -static inline void kvmppc_xive_rearm_escalation(struct kvm_vcpu *vcpu) { }
> +static inline bool kvmppc_xive_rearm_escalation(struct kvm_vcpu *vcpu) { return true; }
>   
>   static inline int kvmppc_xive_enabled(struct kvm_vcpu *vcpu)
>   	{ return 0; }
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 5df359053147..a0b674d3a2da 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -4073,10 +4073,16 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
>   		    !(vcpu->arch.shregs.msr & MSR_PR)) {
>   			unsigned long req = kvmppc_get_gpr(vcpu, 3);
>   
> -			/* H_CEDE has to be handled now, not later */
> +			/* H_CEDE has to be handled now */
>   			if (req == H_CEDE) {
>   				kvmppc_cede(vcpu);
> -				kvmppc_xive_rearm_escalation(vcpu); /* may un-cede */
> +				if (!kvmppc_xive_rearm_escalation(vcpu)) {
> +					/*
> +					 * Pending escalation so abort
> +					 * the cede.
> +					 */
> +					vcpu->arch.ceded = 0;
> +				}
>   				kvmppc_set_gpr(vcpu, 3, 0);
>   				trap = 0;
>   
> diff --git a/arch/powerpc/kvm/book3s_xive.c b/arch/powerpc/kvm/book3s_xive.c
> index e216c068075d..7b513e14cada 100644
> --- a/arch/powerpc/kvm/book3s_xive.c
> +++ b/arch/powerpc/kvm/book3s_xive.c
> @@ -179,12 +179,13 @@ void kvmppc_xive_pull_vcpu(struct kvm_vcpu *vcpu)
>   }
>   EXPORT_SYMBOL_GPL(kvmppc_xive_pull_vcpu);
>   
> -void kvmppc_xive_rearm_escalation(struct kvm_vcpu *vcpu)
> +bool kvmppc_xive_rearm_escalation(struct kvm_vcpu *vcpu)
>   {
>   	void __iomem *esc_vaddr = (void __iomem *)vcpu->arch.xive_esc_vaddr;
> +	bool ret = true;
>   
>   	if (!esc_vaddr)
> -		return;
> +		return ret;
>   
>   	/* we are using XIVE with single escalation */
>   
> @@ -197,7 +198,7 @@ void kvmppc_xive_rearm_escalation(struct kvm_vcpu *vcpu)
>   		 * we also don't want to set xive_esc_on to 1 here in
>   		 * case we race with xive_esc_irq().
>   		 */
> -		vcpu->arch.ceded = 0;
> +		ret = false;
>   		/*
>   		 * The escalation interrupts are special as we don't EOI them.
>   		 * There is no need to use the load-after-store ordering offset
> @@ -210,6 +211,8 @@ void kvmppc_xive_rearm_escalation(struct kvm_vcpu *vcpu)
>   		__raw_readq(esc_vaddr + XIVE_ESB_SET_PQ_00);
>   	}
>   	mb();
> +
> +	return ret;
>   }
>   EXPORT_SYMBOL_GPL(kvmppc_xive_rearm_escalation);
>