linux-kernel - Re: [PATCH 11/67] KVM: SVM: Delete IRTE link from previous vCPU irrespective of new routing

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Message-ID: <d345b636-792f-4762-8c6c-2a7252294068@amd.com>
Date: Tue, 15 Apr 2025 16:36:29 +0530
From: Sairaj Kodilkar <sarunkod@....com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini
	<pbonzini@...hat.com>, Joerg Roedel <joro@...tes.org>, David Woodhouse
	<dwmw2@...radead.org>, Lu Baolu <baolu.lu@...ux.intel.com>
CC: <kvm@...r.kernel.org>, <iommu@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, Maxim Levitsky <mlevitsk@...hat.com>, Joao
 Martins <joao.m.martins@...cle.com>, David Matlack <dmatlack@...gle.com>
Subject: Re: [PATCH 11/67] KVM: SVM: Delete IRTE link from previous vCPU
 irrespective of new routing

On 4/5/2025 1:08 AM, Sean Christopherson wrote:
> Delete the IRTE link from the previous vCPU irrespective of the new
> routing state.  This is a glorified nop (only the ordering changes), as
> both the "posting" and "remapped" mode paths pre-delete the link.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>   arch/x86/kvm/svm/avic.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index 02b6f0007436..e9ded2488a0b 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -870,6 +870,12 @@ int avic_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,
>   	if (!kvm_arch_has_assigned_device(kvm) || !kvm_arch_has_irq_bypass())
>   		return 0;
>   
> +	/*
> +	 * If the IRQ was affined to a different vCPU, remove the IRTE metadata
> +	 * from the *previous* vCPU's list.
> +	 */
> +	svm_ir_list_del(irqfd);
> +
>   	pr_debug("SVM: %s: host_irq=%#x, guest_irq=%#x, set=%#x\n",
>   		 __func__, host_irq, guest_irq, set);
>   
> @@ -892,8 +898,6 @@ int avic_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,
>   
>   		WARN_ON_ONCE(new && memcmp(e, new, sizeof(*new)));
>   
> -		svm_ir_list_del(irqfd);
> -
>   		/**
>   		 * Here, we setup with legacy mode in the following cases:
>   		 * 1. When cannot target interrupt to a specific vcpu.

Hi sean,
Why not combine patch 10 and patch 11 ? Is there a reason to separate
the changes ?

Regards
Sairaj Kodilkar