| Message ID | 1582617278-50338-1-git-send-email-pbonzini@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: SVM: allocate AVIC data structures based on kvm_amd moduleparameter | expand |
Paolo Bonzini <pbonzini@redhat.com> writes: > Even if APICv is disabled at startup, the backing page and ir_list need > to be initialized in case they are needed later. The only case in > which this can be skipped is for userspace irqchip, and that must be > done because avic_init_backing_page dereferences vcpu->arch.apic > (which is NULL for userspace irqchip). > > Tested-by: rmuncrief@humanavance.com > Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=206579 > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > arch/x86/kvm/svm.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > index ad3f5b178a03..bd02526300ab 100644 > --- a/arch/x86/kvm/svm.c > +++ b/arch/x86/kvm/svm.c > @@ -2194,8 +2194,9 @@ static void svm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) > static int avic_init_vcpu(struct vcpu_svm *svm) > { > int ret; > + struct kvm_vcpu *vcpu = &svm->vcpu; > > - if (!kvm_vcpu_apicv_active(&svm->vcpu)) > + if (!avic || !irqchip_in_kernel(vcpu->kvm)) > return 0; > > ret = avic_init_backing_page(&svm->vcpu); Out of pure curiosity, when irqchip_in_kernel() is false, can we still get to .update_pi_irte() (svm_update_pi_irte()) -> get_pi_vcpu_info() -> "vcpu_info->pi_desc_addr = __sme_set(page_to_phys((*svm)->avic_backing_page));" -> crash! or is there anything which make this impossible? The patch is an improvement anyway, so Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
On 25/02/20 14:45, Vitaly Kuznetsov wrote: >> int ret; >> + struct kvm_vcpu *vcpu = &svm->vcpu; >> >> - if (!kvm_vcpu_apicv_active(&svm->vcpu)) >> + if (!avic || !irqchip_in_kernel(vcpu->kvm)) >> return 0; >> >> ret = avic_init_backing_page(&svm->vcpu); > Out of pure curiosity, > > when irqchip_in_kernel() is false, can we still get to .update_pi_irte() > (svm_update_pi_irte()) -> get_pi_vcpu_info() -> "vcpu_info->pi_desc_addr > = __sme_set(page_to_phys((*svm)->avic_backing_page));" -> crash! or is > there anything which make this impossible? No, because kvm_arch_irqfd_allowed returns false so you cannot create any irqfd (svm_update_pi_irte is called when virt/lib/irqbypass.c finds a match between two eventfds in KVM and VFIO). Paolo
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index ad3f5b178a03..bd02526300ab 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -2194,8 +2194,9 @@ static void svm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) static int avic_init_vcpu(struct vcpu_svm *svm) { int ret; + struct kvm_vcpu *vcpu = &svm->vcpu; - if (!kvm_vcpu_apicv_active(&svm->vcpu)) + if (!avic || !irqchip_in_kernel(vcpu->kvm)) return 0; ret = avic_init_backing_page(&svm->vcpu);