linux-kernel - Re: [PATCH v7 14/17] KVM: Update Posted-Interrupts Descriptor when vCPU is preempted

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Message-ID: <55F2B35C.5000000@redhat.com>
Date:	Fri, 11 Sep 2015 12:56:28 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Feng Wu <feng.wu@...el.com>, alex.williamson@...hat.com,
	joro@...tes.org, mtosatti@...hat.com
Cc:	eric.auger@...aro.org, kvm@...r.kernel.org,
	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 14/17] KVM: Update Posted-Interrupts Descriptor when
 vCPU is preempted



On 25/08/2015 10:50, Feng Wu wrote:
> This patch updates the Posted-Interrupts Descriptor when vCPU
> is preempted.
> 
> sched out:
> - Set 'SN' to suppress furture non-urgent interrupts posted for
> the vCPU.
> 
> sched in:
> - Clear 'SN'
> - Change NDST if vCPU is scheduled to a different CPU
> - Set 'NV' to POSTED_INTR_VECTOR
> 
> Signed-off-by: Feng Wu <feng.wu@...el.com>
> ---
>  arch/x86/kvm/vmx.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 51 insertions(+)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 234f720..9c87064 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -45,6 +45,7 @@
>  #include <asm/debugreg.h>
>  #include <asm/kexec.h>
>  #include <asm/apic.h>
> +#include <asm/irq_remapping.h>
>  
>  #include "trace.h"
>  #include "pmu.h"
> @@ -2001,10 +2002,60 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>  		vmcs_writel(HOST_IA32_SYSENTER_ESP, sysenter_esp); /* 22.2.3 */
>  		vmx->loaded_vmcs->cpu = cpu;
>  	}
> +
> +	if (irq_remapping_cap(IRQ_POSTING_CAP)) {
> +		struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
> +		struct pi_desc old, new;
> +		unsigned int dest;
> +
> +		do {
> +			old.control = new.control = pi_desc->control;
> +
> +			/*
> +			 * If 'nv' field is POSTED_INTR_WAKEUP_VECTOR, there
> +			 * are two possible cases:
> +			 * 1. After running 'pi_pre_block', context switch
> +			 *    happened. For this case, 'sn' was set in
> +			 *    vmx_vcpu_put(), so we need to clear it here.
> +			 * 2. After running 'pi_pre_block', we were blocked,
> +			 *    and woken up by some other guy. For this case,
> +			 *    we don't need to do anything, 'pi_post_block'
> +			 *    will do everything for us. However, we cannot
> +			 *    check whether it is case #1 or case #2 here
> +			 *    (maybe, not needed), so we also clear sn here,
> +			 *    I think it is not a big deal.
> +			 */
> +			if (pi_desc->nv != POSTED_INTR_WAKEUP_VECTOR) {
> +				if (vcpu->cpu != cpu) {
> +					dest = cpu_physical_id(cpu);
> +
> +					if (x2apic_enabled())
> +						new.ndst = dest;
> +					else
> +						new.ndst = (dest << 8) & 0xFF00;
> +				}
> +
> +				/* set 'NV' to 'notification vector' */
> +				new.nv = POSTED_INTR_VECTOR;
> +			}
> +
> +			/* Allow posting non-urgent interrupts */
> +			new.sn = 0;
> +		} while (cmpxchg(&pi_desc->control, old.control,
> +				new.control) != old.control);
> +	}
>  }
>  
>  static void vmx_vcpu_put(struct kvm_vcpu *vcpu)
>  {
> +	if (irq_remapping_cap(IRQ_POSTING_CAP)) {
> +		struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
> +
> +		/* Set SN when the vCPU is preempted */
> +		if (vcpu->preempted)
> +			pi_set_sn(pi_desc);
> +	}
> +
>  	__vmx_load_host_state(to_vmx(vcpu));
>  	if (!vmm_exclusive) {
>  		__loaded_vmcs_clear(to_vmx(vcpu)->loaded_vmcs);
> 

Please make this separate functions vmx_vcpu_pi_load and vmx_vcpu_pi_put.

Paolo
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