Re: [PATCH 03/10] KVM: arm/arm64: vgic: Convert struct vgic_lr to use bitfields

From: "Alex Bennée" <alex.bennee@linaro.org>
To: Marc Zyngier <marc.zyngier@arm.com>
Cc: kvm@vger.kernel.org, Andre Przywara <andre.przywara@arm.com>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 03/10] KVM: arm/arm64: vgic: Convert struct vgic_lr to use bitfields
Date: Tue, 09 Jun 2015 14:12:19 +0100	[thread overview]
Message-ID: <87twuh6n64.fsf@linaro.org> (raw)
In-Reply-To: <1433783045-8002-4-git-send-email-marc.zyngier@arm.com>

Marc Zyngier <marc.zyngier@arm.com> writes:

> As we're about to cram more information in the vgic_lr structure
> (HW interrupt number and additional state information), we switch
> to a layout similar to the HW's:
>
> - use bitfields to save space (we don't need more than 10 bits
>   to represent the irq numbers)
> - source CPU and HW interrupt can share the same field, as
>   a SGI doesn't have a physical line.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

> ---
>  include/kvm/arm_vgic.h | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index 133ea00..4f9fa1d 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -95,11 +95,15 @@ enum vgic_type {
>  #define LR_STATE_ACTIVE		(1 << 1)
>  #define LR_STATE_MASK		(3 << 0)
>  #define LR_EOI_INT		(1 << 2)
> +#define LR_HW			(1 << 3)
>  
>  struct vgic_lr {
> -	u16	irq;
> -	u8	source;
> -	u8	state;
> +	unsigned irq:10;
> +	union {
> +		unsigned hwirq:10;
> +		unsigned source:8;
> +	};
> +	unsigned state:4;
>  };
>  
>  struct vgic_vmcr {

-- 
Alex Bennée
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