linux-kernel - Re: [PATCH v1 06/11] KVM: x86: use hardware-compatible format for APIC ID register

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Date:	Fri, 1 Jul 2016 10:33:20 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Radim Krčmář <rkrcmar@...hat.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:	"Lan, Tianyu" <tianyu.lan@...el.com>,
	Igor Mammedov <imammedo@...hat.com>,
	Jan Kiszka <jan.kiszka@....de>, Peter Xu <peterx@...hat.com>
Subject: Re: [PATCH v1 06/11] KVM: x86: use hardware-compatible format for
 APIC ID register

On 30/06/2016 22:54, Radim Krčmář wrote:
> +static void __kvm_apic_state_fixup(struct kvm_vcpu *vcpu,
> +		struct kvm_lapic_state *s, bool set)
> +{
> +	if (apic_x2apic_mode(vcpu->arch.apic)) {
> +		u32 *id = (u32 *)(s->regs + APIC_ID);
> +		if (set)
> +			*id >>= 24;
> +		else
> +			*id <<= 24;
> +	}

When setting, this should read from the apic_base being set.  So I think
you cannot use apic_x2apic_mode.

With this change, you don't need the struct kvm_vcpu argument now; add a
struct kvm argument instead in patch 10.

> @@ -2780,6 +2780,7 @@ static int kvm_vcpu_ioctl_get_lapic(struct kvm_vcpu *vcpu,
>  		kvm_x86_ops->sync_pir_to_irr(vcpu);
>  
>  	memcpy(s->regs, vcpu->arch.apic->regs, sizeof *s);
> +	kvm_apic_state_get_fixup(vcpu, s);

Instead of kvm_apic_state_get/set_fixup, group the memcpy and
__kvm_apic_state_fixup in a new function kvm_apic_get_state(struct
kvm_lapic *apic, char *regs).

>  	return 0;
>  }
> @@ -2787,6 +2788,7 @@ static int kvm_vcpu_ioctl_get_lapic(struct kvm_vcpu *vcpu,
>  static int kvm_vcpu_ioctl_set_lapic(struct kvm_vcpu *vcpu,
>  				    struct kvm_lapic_state *s)
>  {
> +	kvm_apic_state_set_fixup(vcpu, s);
>  	kvm_apic_post_state_restore(vcpu, s);

... and likewise merge these two in a refactored
kvm_apic_post_state_restore called kvm_apic_set_state(struct kvm_lapic
*apic, char *regs), by calling __kvm_apic_state_fixup before
kvm_apic_post_state_restore's memcpy.

With these changes I guess there's no need for the underscores in
__kvm_apic_state_fixup.  And you can also change the struct
kvm_lapic_state pointer in the function to a char *.

Thanks,

Paolo