linux-kernel - Re: [PATCH 30/67] KVM: VMX: Stop walking list of routing table entries when updating IRTE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aCznzZ-SN4Pf_htE@google.com>
Date: Tue, 20 May 2025 13:36:29 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: Joerg Roedel <joro@...tes.org>, David Woodhouse <dwmw2@...radead.org>, 
	Lu Baolu <baolu.lu@...ux.intel.com>, 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 30/67] KVM: VMX: Stop walking list of routing table
 entries when updating IRTE

On Tue, Apr 08, 2025, Paolo Bonzini wrote:
> On 4/4/25 21:38, Sean Christopherson wrote:
> > Now that KVM provides the to-be-updated routing entry, stop walking the
> > routing table to find that entry.  KVM, via setup_routing_entry() and
> > sanity checked by kvm_get_msi_route(), disallows having a GSI configured
> > to trigger multiple MSIs, i.e. the for-loop can only process one entry.
> > 
> > Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> > ---
> >   arch/x86/kvm/vmx/posted_intr.c | 100 +++++++++++----------------------
> >   1 file changed, 33 insertions(+), 67 deletions(-)
> > 
> > diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
> > index 00818ca30ee0..786912cee3f8 100644
> > --- a/arch/x86/kvm/vmx/posted_intr.c
> > +++ b/arch/x86/kvm/vmx/posted_intr.c
> > @@ -268,78 +268,44 @@ int vmx_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,
> >   		       unsigned int host_irq, uint32_t guest_irq,
> >   		       struct kvm_kernel_irq_routing_entry *new)
> >   {
> > -	struct kvm_kernel_irq_routing_entry *e;
> > -	struct kvm_irq_routing_table *irq_rt;
> > -	bool enable_remapped_mode = true;
> >   	struct kvm_lapic_irq irq;
> >   	struct kvm_vcpu *vcpu;
> >   	struct vcpu_data vcpu_info;
> > -	bool set = !!new;
> > -	int idx, ret = 0;
> >   	if (!vmx_can_use_vtd_pi(kvm))
> >   		return 0;
> > -	idx = srcu_read_lock(&kvm->irq_srcu);
> > -	irq_rt = srcu_dereference(kvm->irq_routing, &kvm->irq_srcu);
> > -	if (guest_irq >= irq_rt->nr_rt_entries ||
> > -	    hlist_empty(&irq_rt->map[guest_irq])) {
> > -		pr_warn_once("no route for guest_irq %u/%u (broken user space?)\n",
> > -			     guest_irq, irq_rt->nr_rt_entries);
> > -		goto out;
> > -	}
> > -
> > -	hlist_for_each_entry(e, &irq_rt->map[guest_irq], link) {
> > -		if (e->type != KVM_IRQ_ROUTING_MSI)
> > -			continue;
> > -
> > -		WARN_ON_ONCE(new && memcmp(e, new, sizeof(*new)));
> 
> Alternatively, if you want to keep patches 28/29 separate, you could add
> this WARN_ON_ONCE to avic.c in the exact same place after checking e->type
> -- not so much for asserting purposes, but more to document what's going on
> for the reviewer.

FWIW, AVIC already has the same WARN, they were both added by "KVM: x86: Pass new
routing entries and irqfd when updating IRTEs".

That said, I agree that squashing 28/29 is the way to go, especially since I didn't
isolate the changes for VMX (I've no idea why I did for SVM but not VMX).