linux-kernel - Re: [PATCH v2 25/43] KVM: VMX: Save/restore IRQs (instead of CLI/STI) during PI pre/post block

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Date:   Thu, 28 Oct 2021 13:54:40 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Marc Zyngier <maz@...nel.org>,
        Huacai Chen <chenhuacai@...nel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
        Paul Mackerras <paulus@...abs.org>,
        Anup Patel <anup.patel@....com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Atish Patra <atish.patra@....com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-mips@...r.kernel.org, kvm@...r.kernel.org,
        kvm-ppc@...r.kernel.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        David Matlack <dmatlack@...gle.com>,
        Oliver Upton <oupton@...gle.com>,
        Jing Zhang <jingzhangos@...gle.com>
Subject: Re: [PATCH v2 25/43] KVM: VMX: Save/restore IRQs (instead of
 CLI/STI) during PI pre/post block

On Fri, 2021-10-08 at 19:12 -0700, Sean Christopherson wrote:
> Save/restore IRQs when disabling IRQs in posted interrupt pre/post block
> in preparation for moving the code into vcpu_put/load(), and thus may be
> called with IRQs already disabled.
> 
> No functional changed intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  arch/x86/kvm/vmx/posted_intr.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
> index 239e0e72a0dd..414ea6972b5c 100644
> --- a/arch/x86/kvm/vmx/posted_intr.c
> +++ b/arch/x86/kvm/vmx/posted_intr.c
> @@ -140,6 +140,7 @@ int pi_pre_block(struct kvm_vcpu *vcpu)
>  {
>  	struct pi_desc old, new;
>  	struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
> +	unsigned long flags;
>  
>  	if (!kvm_arch_has_assigned_device(vcpu->kvm) ||
>  	    !irq_remapping_cap(IRQ_POSTING_CAP) ||
> @@ -147,8 +148,7 @@ int pi_pre_block(struct kvm_vcpu *vcpu)
>  	    vmx_interrupt_blocked(vcpu))
>  		return 0;
>  
> -	WARN_ON(irqs_disabled());
> -	local_irq_disable();
> +	local_irq_save(flags);
>  
>  	vcpu->pre_pcpu = vcpu->cpu;
>  	spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->cpu));
> @@ -171,19 +171,20 @@ int pi_pre_block(struct kvm_vcpu *vcpu)
>  	if (pi_test_on(pi_desc))
>  		__pi_post_block(vcpu);
>  
> -	local_irq_enable();
> +	local_irq_restore(flags);
>  	return (vcpu->pre_pcpu == -1);
>  }
>  
>  void pi_post_block(struct kvm_vcpu *vcpu)
>  {
> +	unsigned long flags;
> +
>  	if (vcpu->pre_pcpu == -1)
>  		return;
>  
> -	WARN_ON(irqs_disabled());
> -	local_irq_disable();
> +	local_irq_save(flags);
>  	__pi_post_block(vcpu);
> -	local_irq_enable();
> +	local_irq_restore(flags);
>  }
>  
>  /*
Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>

Best regards,
	Maxim Levitsky