From mboxrd@z Thu Jan  1 00:00:00 1970
From: Julien Grall <julien.grall@citrix.com>
Subject: Re: [PATCH v6 23/31] xen/arm: ITS: Add 32-bit access to
 GICR_TYPER
Date: Mon, 31 Aug 2015 17:06:16 +0100
Message-ID: <55E47B78.8070603@citrix.com>
References: <1441019208-2764-1-git-send-email-vijay.kilari@gmail.com>
	<1441019208-2764-24-git-send-email-vijay.kilari@gmail.com>
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To: vijay.kilari@gmail.com, Ian.Campbell@citrix.com, stefano.stabellini@eu.citrix.com, stefano.stabellini@citrix.com, tim@xen.org, xen-devel@lists.xen.org
Cc: Prasun.Kapoor@caviumnetworks.com, Vijaya Kumar K <Vijaya.Kumar@caviumnetworks.com>, manish.jaggi@caviumnetworks.com
List-Id: xen-devel@lists.xenproject.org

Hi Vijay,

On 31/08/2015 12:06, vijay.kilari@gmail.com wrote:
> From: Vijaya Kumar K <Vijaya.Kumar@caviumnetworks.com>
>
> Add support to read 32-bit access to GICR_TYPER register
>
> Signed-off-by: Vijaya Kumar K <Vijaya.Kumar@caviumnetworks.com>
> ---
>   xen/arch/arm/vgic-v3.c |    6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
> index 771bfd1..4caac5e 100644
> --- a/xen/arch/arm/vgic-v3.c
> +++ b/xen/arch/arm/vgic-v3.c
> @@ -122,6 +122,7 @@ static int __vgic_v3_rdistr_rd_mmio_read(struct vcpu *v, mmio_info_t *info,
>           *r = vgic_reg32_read(GICV3_GICR_IIDR_VAL, info);
>           return 1;
>       case GICR_TYPER:
> +    case GICR_TYPER + 4:

While I understand this...

>       {
>           uint64_t typer, aff;
>
> @@ -136,7 +137,10 @@ static int __vgic_v3_rdistr_rd_mmio_read(struct vcpu *v, mmio_info_t *info,
>           if ( v->arch.vgic.flags & VGIC_V3_RDIST_LAST )
>               typer |= GICR_TYPER_LAST;
>
> -        *r = vgic_reg64_read(typer, info);
> +        if ( dabt.size == DABT_DOUBLE_WORD )
> +            *r = vgic_reg64_read(typer, info);
> +        else
> +            *r = vgic_reg32_read(typer, info);

can you explain why this is necessary? The goal of vgic_reg64_read is to 
handle all access size to 64bit register.
The vgic_reg32_read will only handle access on 32bit and therefore it 
won't be possible to access to the most significant word.

Regards,

-- 
Julien Grall