----- pbonzini@xxxxxxxxxx wrote:
> The initial reset of the local APIC is performed before the VMCS has
> been
> created, but it tries to do a vmwrite:
>
> vmwrite error: reg 810 value 4a00 (err 18944)
> CPU: 54 PID: 38652 Comm: qemu-kvm Tainted: G W I
> 4.16.0-0.rc2.git0.1.fc28.x86_64 #1
> Hardware name: Intel Corporation S2600CW/S2600CW, BIOS
> SE5C610.86B.01.01.0003.090520141303 09/05/2014
> Call Trace:
> vmx_set_rvi [kvm_intel]
> vmx_hwapic_irr_update [kvm_intel]
> kvm_lapic_reset [kvm]
> kvm_create_lapic [kvm]
> kvm_arch_vcpu_init [kvm]
> kvm_vcpu_init [kvm]
> vmx_create_vcpu [kvm_intel]
> kvm_vm_ioctl [kvm]
>
> Move it later, after the VMCS has been created.
>
> Fixes: 851c1a18c5412fd321e387cfe60739387cdbf37d
> Cc: Liran Alon <liran.alon@xxxxxxxxxx>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> arch/x86/kvm/lapic.c | 1 -
> arch/x86/kvm/x86.c | 1 +
> 2 files changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 924ac8ce9d50..cc5fe7a50dde 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -2165,7 +2165,6 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu)
> */
> vcpu->arch.apic_base = MSR_IA32_APICBASE_ENABLE;
> static_key_slow_inc(&apic_sw_disabled.key); /* sw disabled at reset
> */
> - kvm_lapic_reset(vcpu, false);
> kvm_iodevice_init(&apic->dev, &apic_mmio_ops);
>
> return 0;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index c8a0b545ac20..ca90d9515137 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7975,6 +7975,7 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
> kvm_vcpu_mtrr_init(vcpu);
> vcpu_load(vcpu);
> kvm_vcpu_reset(vcpu, false);
> + kvm_lapic_reset(vcpu, false);
> kvm_mmu_setup(vcpu);
> vcpu_put(vcpu);
> return 0;
> --
> 1.8.3.1
I agree with the bug and the fix.
It makes sense to reset LAPIC in the same place other components are reset
rather than in it's creation.
However, I failed to understand why you mention it fixes commit:
851c1a18c541 ("KVM: nVMX: Fix injection to L2 when L1 don't intercept external-interrupts")
Before and after that commit, vmx_hwapic_irr_update() did exactly the same
because is_guest_mode(vcpu)==false at this point.
Therefore, vmx_hwapic_irr_update() has always just called vmx_set_rvi()
which has not changed in that commit.
It seems to me that the commit which introduced this issue is actually:
4191db26b714 ("KVM: x86: Update APICv on APIC reset")
What am I missing?
-Liran
