On Mon, May 06, 2024, Yi Wang wrote:
> From: Yi Wang <foxywang@xxxxxxxxxxx>
>
> As we have setup empty irq routing in kvm_create_vm(), there's
> no need to setup dummy routing when KVM_CREATE_IRQCHIP.
>
> Signed-off-by: Yi Wang <foxywang@xxxxxxxxxxx>
> ---
> arch/s390/kvm/kvm-s390.c | 9 +--------
> 1 file changed, 1 insertion(+), 8 deletions(-)
>
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 5147b943a864..ba7fd39bcbf4 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -2998,14 +2998,7 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
> break;
> }
> case KVM_CREATE_IRQCHIP: {
> - struct kvm_irq_routing_entry routing;
> -
> - r = -EINVAL;
> - if (kvm->arch.use_irqchip) {
> - /* Set up dummy routing. */
> - memset(&routing, 0, sizeof(routing));
> - r = kvm_set_irq_routing(kvm, &routing, 0, 0);
> - }
> + r = 0;
This is wrong, KVM_CREATE_IRQCHIP should fail with -EINVAL if kvm->arch.use_irqchip
is false.
There's also a functional change here, though I highly doubt it negatively affects
userspace. Nothing in s390 prevents invoking KVM_CREATE_IRQCHIP after
KVM_SET_GSI_ROUTING, so userspace could very theoretically use KVM_CREATE_IRQCHIP
to reset to empty IRQ routing.
Christian, if it works for you, I'll massage it to this when applying.
--
From: Yi Wang <foxywang@xxxxxxxxxxx>
Date: Mon, 6 May 2024 18:17:51 +0800
Subject: [PATCH] KVM: s390: Don't re-setup dummy routing when
KVM_CREATE_IRQCHIP
Now that KVM sets up empty irq routing in kvm_create_vm(), there's
no need to setup dummy routing when KVM_CREATE_IRQCHIP.
Note, userspace could very theoretically use KVM_CREATE_IRQCHIP after
KVM_SET_GSI_ROUTING to reset to empty IRQ routing, but it's extremely
unlikely any VMM does that, e.g. the main reason s390 does anything for
KVM_CREATE_IRQCHIP is to that s390 doesn't need to be special cased by the
VMM.
Signed-off-by: Yi Wang <foxywang@xxxxxxxxxxx>
Acked-by: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240506101751.3145407-4-foxywang@xxxxxxxxxxx
[sean: keep use_irqchip check, call out KVM_SET_GSI_ROUTING impact]
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/s390/kvm/kvm-s390.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 82e9631cd9ef..4641083ee100 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2996,14 +2996,9 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
break;
}
case KVM_CREATE_IRQCHIP: {
- struct kvm_irq_routing_entry routing;
-
r = -EINVAL;
- if (kvm->arch.use_irqchip) {
- /* Set up dummy routing. */
- memset(&routing, 0, sizeof(routing));
- r = kvm_set_irq_routing(kvm, &routing, 0, 0);
- }
+ if (kvm->arch.use_irqchip)
+ r = 0;
break;
}
case KVM_SET_DEVICE_ATTR: {
base-commit: 9a859becf1b7f6879466e8c0ebee492b236f2080
--
