Re: [Xen-devel] [PATCH v6 23/31] xen/arm: ITS: Add 32-bit access to GICR_TYPER

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Vijay,

On 31/08/2015 12:06, vijay.kilari@xxxxxxxxx wrote:
> From: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxxxxxxxxxx>
>
> Add support to read 32-bit access to GICR_TYPER register
>
> Signed-off-by: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxxxxxxxxxx>
> ---
>   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

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