Re: [PATCH v5 7/8] KVM: VMX: Update PID-pointer table entry when APIC ID is changed

[Zeng Guang]

On 1/6/2022 3:13 AM, Tom Lendacky wrote:
> On 12/31/21 8:28 AM, Zeng Guang wrote:
> > In xAPIC mode, guest is allowed to modify APIC ID at runtime.
> > If IPI virtualization is enabled, corresponding entry in
> > PID-pointer table need change accordingly.
> >
> > Signed-off-by: Zeng Guang <guang.zeng@xxxxxxxxx>
> > ---
> >    arch/x86/include/asm/kvm_host.h |  1 +
> >    arch/x86/kvm/lapic.c            |  7 +++++--
> >    arch/x86/kvm/vmx/vmx.c          | 12 ++++++++++++
> >    3 files changed, 18 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index 2164b9f4c7b0..753bf2a7cebc 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -1493,6 +1493,7 @@ struct kvm_x86_ops {
> >    	int (*complete_emulated_msr)(struct kvm_vcpu *vcpu, int err);
> >    
> >    	void (*vcpu_deliver_sipi_vector)(struct kvm_vcpu *vcpu, u8 vector);
> > +	void (*update_ipiv_pid_entry)(struct kvm_vcpu *vcpu, u8 old_id, u8 new_id);
> >    };
> >    
> >    struct kvm_x86_nested_ops {
> > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> > index 3ce7142ba00e..83c2c7594bcd 100644
> > --- a/arch/x86/kvm/lapic.c
> > +++ b/arch/x86/kvm/lapic.c
> > @@ -2007,9 +2007,12 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
> >    
> >    	switch (reg) {
> >    	case APIC_ID:		/* Local APIC ID */
> > -		if (!apic_x2apic_mode(apic))
> > +		if (!apic_x2apic_mode(apic)) {
> > +			u8 old_id = kvm_lapic_get_reg(apic, APIC_ID) >> 24;
> > +
> >    			kvm_apic_set_xapic_id(apic, val >> 24);
> > -		else
> > +			kvm_x86_ops.update_ipiv_pid_entry(apic->vcpu, old_id, val >> 24);
> Won't this blow up on AMD since there is no corresponding SVM op?
>
> Thanks,
> Tom
Right, need check ops validness to avoid ruining AMD system. Same 
consideration on ops "update_ipiv_pid_table" in patch8.
I will revise in next version. Thanks.
> > +		} else
> >    			ret = 1;
> >    		break;
> >