linux-kernel - Re: [PATCH v3 00/26] KVM: x86: Halt and APICv overhaul

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Message-ID: <3bf8d500-0c1e-92dd-20c8-c3c231d2cbed@redhat.com>
Date:   Thu, 9 Dec 2021 15:29:04 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Cc:     Joerg Roedel <joro@...tes.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        kvm@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 00/26] KVM: x86: Halt and APICv overhaul

On 12/9/21 01:02, Sean Christopherson wrote:
> RDX, a.k.a. ir_data is NULL.  This check in svm_ir_list_add()
> 
> 	if (pi->ir_data && (pi->prev_ga_tag != 0)) {
> 
> implies pi->ir_data can be NULL, but neither avic_update_iommu_vcpu_affinity()
> nor amd_iommu_update_ga() check ir->data for NULL.
> 
> amd_ir_set_vcpu_affinity() returns "success" without clearing pi.is_guest_mode
> 
> 	/* Note:
> 	 * This device has never been set up for guest mode.
> 	 * we should not modify the IRTE
> 	 */
> 	if (!dev_data || !dev_data->use_vapic)
> 		return 0;
> 
> so it's plausible svm_ir_list_add() could add to the list with a NULL pi->ir_data.
> 
> But none of the relevant code has seen any meaningful changes since 5.15, so odds
> are good I broke something :-/
> 

Ok, I'll take this.

Paolo