Re: [Xen-devel] [PATCH v3] xen/arm: Handle unimplemented VGICv3 dist registers as RAZ/WI

[Julien Grall <julien@xen.org>]

Hi Jeff,

As you now handle GICR register, I would drop "dist" from the title.

On 04/02/2020 19:51, Jeff Kubascik wrote:
> Per the ARM Generic Interrupt Controller Architecture Specification (ARM
> IHI 0069E), reserved registers should generally be treated as RAZ/WI.
> To simplify the VGICv3 design and improve guest compatibility, treat the
> default case for GICD and GICR registers as read_as_zero/write_ignore.
> 
> Signed-off-by: Jeff Kubascik <jeff.kubascik@dornerworks.com>

Acked-by: Julien Grall <julien@xen.org>

I will update the commit title while committing the patch.

> ---
> Changes in v3:
> - Fixed spelling error in commit message
> - Dropped misleading comments that were added in v2
> - Added printk back in for default case
> - Implemented RAZ/WI for the redist registers as well
> - Update commit message to include GICR scope
> ---
>   xen/arch/arm/vgic-v3.c | 22 ++++++++++++++++------
>   1 file changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
> index 422b94f902..4e60ba15cc 100644
> --- a/xen/arch/arm/vgic-v3.c
> +++ b/xen/arch/arm/vgic-v3.c
> @@ -320,7 +320,7 @@ static int __vgic_v3_rdistr_rd_mmio_read(struct vcpu *v, mmio_info_t *info,
>           printk(XENLOG_G_ERR
>                  "%pv: vGICR: unhandled read r%d offset %#08x\n",
>                  v, dabt.reg, gicr_reg);
> -        return 0;
> +        goto read_as_zero;
>       }
>   bad_width:
>       printk(XENLOG_G_ERR "%pv vGICR: bad read width %d r%d offset %#08x\n",
> @@ -337,6 +337,10 @@ read_as_zero_32:
>       *r = 0;
>       return 1;
>   
> +read_as_zero:
> +    *r = 0;
> +    return 1;
> +
>   read_impl_defined:
>       printk(XENLOG_G_DEBUG
>              "%pv: vGICR: RAZ on implementation defined register offset %#08x\n",
> @@ -638,7 +642,7 @@ static int __vgic_v3_rdistr_rd_mmio_write(struct vcpu *v, mmio_info_t *info,
>       default:
>           printk(XENLOG_G_ERR "%pv: vGICR: unhandled write r%d offset %#08x\n",
>                  v, dabt.reg, gicr_reg);
> -        return 0;
> +        goto write_ignore;
>       }
>   bad_width:
>       printk(XENLOG_G_ERR
> @@ -654,6 +658,9 @@ write_ignore_32:
>       if ( dabt.size != DABT_WORD ) goto bad_width;
>       return 1;
>   
> +write_ignore:
> +    return 1;
> +
>   write_impl_defined:
>       printk(XENLOG_G_DEBUG
>              "%pv: vGICR: WI on implementation defined register offset %#08x\n",
> @@ -925,7 +932,7 @@ static int vgic_v3_rdistr_sgi_mmio_read(struct vcpu *v, mmio_info_t *info,
>           printk(XENLOG_G_ERR
>                  "%pv: vGICR: SGI: unhandled read r%d offset %#08x\n",
>                  v, dabt.reg, gicr_reg);
> -        return 0;
> +        goto read_as_zero;
>       }
>   bad_width:
>       printk(XENLOG_G_ERR "%pv: vGICR: SGI: bad read width %d r%d offset %#08x\n",
> @@ -1002,7 +1009,7 @@ static int vgic_v3_rdistr_sgi_mmio_write(struct vcpu *v, mmio_info_t *info,
>           printk(XENLOG_G_ERR
>                  "%pv: vGICR: SGI: unhandled write r%d offset %#08x\n",
>                  v, dabt.reg, gicr_reg);
> -        return 0;
> +        goto write_ignore;
>       }
>   
>   bad_width:
> @@ -1014,6 +1021,9 @@ bad_width:
>   write_ignore_32:
>       if ( dabt.size != DABT_WORD ) goto bad_width;
>       return 1;
> +
> +write_ignore:
> +    return 1;
>   }
>   
>   static struct vcpu *get_vcpu_from_rdist(struct domain *d,
> @@ -1252,7 +1262,7 @@ static int vgic_v3_distr_mmio_read(struct vcpu *v, mmio_info_t *info,
>       default:
>           printk(XENLOG_G_ERR "%pv: vGICD: unhandled read r%d offset %#08x\n",
>                  v, dabt.reg, gicd_reg);
> -        return 0;
> +        goto read_as_zero;
>       }
>   
>   bad_width:
> @@ -1438,7 +1448,7 @@ static int vgic_v3_distr_mmio_write(struct vcpu *v, mmio_info_t *info,
>           printk(XENLOG_G_ERR
>                  "%pv: vGICD: unhandled write r%d=%"PRIregister" offset %#08x\n",
>                  v, dabt.reg, r, gicd_reg);
> -        return 0;
> +        goto write_ignore;
>       }
>   
>   bad_width:
> 

Cheers,

-- 
Julien Grall

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