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

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Message-ID: <346f5a5e93077ba20188a9b0e67bb3a44e2cad48.camel@redhat.com>
Date:   Thu, 09 Dec 2021 16:48:25 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.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 Thu, 2021-12-09 at 15:29 +0100, Paolo Bonzini wrote:
> 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 :-/

Doesn't reproduce here yet even with my iommu changes :-(
Oh well.

Best regards,
	Maxim Levitsky


> > 
> 
> Ok, I'll take this.
> 
> Paolo
>