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

[Jeff Kubascik <jeff.kubascik@xxxxxxxxxxxxxxx>]

Hey Julien,

On 2/8/2020 7:05 AM, Julien Grall wrote:
> Hi Jeff,
> 
> As you now handle GICR register, I would drop "dist" from the title.
> 

Good catch, I missed this in 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@xxxxxxxxxxxxxxx>
> 
> Acked-by: Julien Grall <julien@xxxxxxx>
> 
> I will update the commit title while committing the patch.

Thank you!

>> ---
>> 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
> 

Sincerely,
Jeff Kubascik

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