Re: [PATCH 4/5] KVM: x86: Use kvm_get_vcpu() instead of open-coded access
From: Sean Christopherson <seanjc@google.com>
Date: 2021-11-05 20:04:46
Also in:
kvm, kvmarm, linux-mips
Subsystem:
kernel virtual machine for x86 (kvm/x86), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Sean Christopherson, Paolo Bonzini, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
On Fri, Nov 05, 2021, Marc Zyngier wrote:
quoted hunk ↗ jump to hunk
As we are about to change the way vcpus are allocated, mandate the use of kvm_get_vcpu() instead of open-coding the access. Signed-off-by: Marc Zyngier <maz@kernel.org> --- arch/x86/kvm/vmx/posted_intr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c index 5f81ef092bd4..82a49720727d 100644 --- a/arch/x86/kvm/vmx/posted_intr.c +++ b/arch/x86/kvm/vmx/posted_intr.c@@ -272,7 +272,7 @@ int pi_update_irte(struct kvm *kvm, unsigned int host_irq, uint32_t guest_irq, if (!kvm_arch_has_assigned_device(kvm) || !irq_remapping_cap(IRQ_POSTING_CAP) || - !kvm_vcpu_apicv_active(kvm->vcpus[0])) + !kvm_vcpu_apicv_active(kvm_get_vcpu(kvm, 0)))
Huh. The existing code is decidedly odd. I think it might even be broken, as it's not obvious that vCPU0 _must_ be created when e.g. kvm_arch_irq_bypass_add_producer() is called. An equivalent, safe check would be:
diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
index 5f81ef092bd4..a3100591a9ca 100644
--- a/arch/x86/kvm/vmx/posted_intr.c
+++ b/arch/x86/kvm/vmx/posted_intr.c@@ -272,7 +272,7 @@ int pi_update_irte(struct kvm *kvm, unsigned int host_irq, uint32_t guest_irq, if (!kvm_arch_has_assigned_device(kvm) || !irq_remapping_cap(IRQ_POSTING_CAP) || - !kvm_vcpu_apicv_active(kvm->vcpus[0])) + !kvm_apicv_activated(kvm)) return 0; idx = srcu_read_lock(&kvm->irq_srcu);
But I think even that is flawed, as APICv can be dynamically deactivated and re-activated while the VM is running, and I don't see a path that re-updates the IRTE when APICv is re-activated. So I think a more conservative check is needed, e.g.
diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
index 5f81ef092bd4..6cf5b2e86118 100644
--- a/arch/x86/kvm/vmx/posted_intr.c
+++ b/arch/x86/kvm/vmx/posted_intr.c@@ -272,7 +272,7 @@ int pi_update_irte(struct kvm *kvm, unsigned int host_irq, uint32_t guest_irq, if (!kvm_arch_has_assigned_device(kvm) || !irq_remapping_cap(IRQ_POSTING_CAP) || - !kvm_vcpu_apicv_active(kvm->vcpus[0])) + !irqchip_in_kernel(kvm) || !enable_apicv) return 0; idx = srcu_read_lock(&kvm->irq_srcu);
Paolo, am I missing something?