Messages in this thread | | | Subject | Re: [PATCH] svm/avic: Allow avic_vcpu_load logic to support host APIC ID 255 | From | "Graf, Alexander" <> | Date | Tue, 7 May 2019 16:16:19 +0200 |
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On 03.05.19 15:37, Suthikulpanit, Suravee wrote: > Current logic does not allow VCPU to be loaded onto CPU with > APIC ID 255. This should be allowed since the host physical APIC ID > field in the AVIC Physical APIC table entry is an 8-bit value, > and APIC ID 255 is valid in system with x2APIC enabled. > > Instead, do not allow VCPU load if the host APIC ID cannot be > represented by an 8-bit value. > > Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Your comment for AVIC_MAX_PHYSICAL_ID_COUNT says that 0xff (255) is broadcast hence you disallow that value. In fact, even the comment a few lines above the patch hunk does say that. Why the change of mind?
Alex
> --- > arch/x86/kvm/svm.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > index 294448e..122788f 100644 > --- a/arch/x86/kvm/svm.c > +++ b/arch/x86/kvm/svm.c > @@ -2071,7 +2071,11 @@ static void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu) > if (!kvm_vcpu_apicv_active(vcpu)) > return; > > - if (WARN_ON(h_physical_id >= AVIC_MAX_PHYSICAL_ID_COUNT)) > + /* > + * Since the host physical APIC id is 8 bits, > + * we can support host APIC ID upto 255. > + */ > + if (WARN_ON(h_physical_id > AVIC_MAX_PHYSICAL_ID_COUNT)) > return; > > entry = READ_ONCE(*(svm->avic_physical_id_cache)); >
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