Re: [PATCH 3/4] KVM: x86: Reject KVM_CREATE_IRQCHIP if APIC base is already mapped

[Sean Christopherson <seanjc@google.com>]

On Mon, Jul 06, 2026, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [High] Calling `gfn_to_memslot()` in `KVM_CREATE_IRQCHIP` without holding the SRCU read lock (`kvm->srcu`) or the memslots update lock (`kvm->slots_lock`) leads to a Use-After-Free and triggers a lockdep warning.
> --
> 
> commit 69e98e42c78858b7858a1956e233c569faf47ae1
> Author: Tim Wiederhake <twiederh@redhat.com>
> 
> KVM: x86: Reject KVM_CREATE_IRQCHIP if APIC base is already mapped
> 
> User space must not map guest memory that covers the default APIC base
> address when using an in-kernel irqchip. This commit adds an explicit
> check to KVM_CREATE_IRQCHIP so the conflict is reported at the point
> where the constraint takes effect.
> 
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> [ ... ]
> > @@ -4413,6 +4413,10 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
> >  		if (kvm->created_vcpus)
> >  			goto create_irqchip_unlock;
> >  
> > +		r = -EEXIST;
> > +		if (gfn_to_memslot(kvm, gpa_to_gfn(APIC_DEFAULT_PHYS_BASE)))

kvm_is_gpa_in_memslot() is what you want.