Re: [Qemu-devel] [PATCH v3 09/13] pc: kvm_apic: pass APIC ID depending on xAPIC/x2APIC mode

[Radim Krčmář]

2016-10-13 11:52+0200, Igor Mammedov:
> Signed-off-by: Igor Mammedov <address@hidden>
> ---
> v4:
>  - drop kvm_has_x2apic_api() and reuse kvm_enable_x2apic() instead
> ---

Reviewed-by: Radim Krčmář <address@hidden>

>  hw/i386/kvm/apic.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/i386/kvm/apic.c b/hw/i386/kvm/apic.c
> index be55102..9a7dd03 100644
> --- a/hw/i386/kvm/apic.c
> +++ b/hw/i386/kvm/apic.c
> @@ -34,7 +34,11 @@ static void kvm_put_apic_state(APICCommonState *s, struct 
> kvm_lapic_state *kapic
>      int i;
>  
>      memset(kapic, 0, sizeof(*kapic));
> -    kvm_apic_set_reg(kapic, 0x2, s->id << 24);
> +    if (kvm_enable_x2apic() && s->apicbase & MSR_IA32_APICBASE_EXTD) {

This will enable x2apic broadcast quirk even if a machine has no way of
using the standard x2APIC mode, so we'd change behavior if an OS
configured a device for broadcast.

I think Linux is the only user of the paravirtual x2APIC mode and it
doesn't configure devices for broadcast, so I think we're safe with it.

Thinking back, I could have just given it a non-controllable capability
in KVM ...

> +        kvm_apic_set_reg(kapic, 0x2, s->initial_apic_id);
> +    } else {
> +        kvm_apic_set_reg(kapic, 0x2, s->id << 24);
> +    }
>      kvm_apic_set_reg(kapic, 0x8, s->tpr);
>      kvm_apic_set_reg(kapic, 0xd, s->log_dest << 24);
>      kvm_apic_set_reg(kapic, 0xe, s->dest_mode << 28 | 0x0fffffff);
> @@ -59,7 +63,11 @@ void kvm_get_apic_state(DeviceState *dev, struct 
> kvm_lapic_state *kapic)
>      APICCommonState *s = APIC_COMMON(dev);
>      int i, v;
>  
> -    s->id = kvm_apic_get_reg(kapic, 0x2) >> 24;
> +    if (kvm_enable_x2apic() && s->apicbase & MSR_IA32_APICBASE_EXTD) {
> +        assert(kvm_apic_get_reg(kapic, 0x2) == s->initial_apic_id);
> +    } else {
> +        s->id = kvm_apic_get_reg(kapic, 0x2) >> 24;
> +    }
>      s->tpr = kvm_apic_get_reg(kapic, 0x8);
>      s->arb_id = kvm_apic_get_reg(kapic, 0x9);
>      s->log_dest = kvm_apic_get_reg(kapic, 0xd) >> 24;
> -- 
> 2.7.4
> 
>