Re: [PATCH v4 1/8] KVM: arm64: vgic-v3: Fix some error codes when setting RDIST base

[Auger Eric <eric.auger@redhat.com>]

Hi Marc,

On 4/1/21 12:52 PM, Marc Zyngier wrote:
> Hi Eric,
> 
> On Thu, 01 Apr 2021 09:52:31 +0100,
> Eric Auger <eric.auger@redhat.com> wrote:
>>
>> KVM_DEV_ARM_VGIC_GRP_ADDR group doc says we should return
>> -EEXIST in case the base address of the redist is already set.
>> We currently return -EINVAL.
>>
>> However we need to return -EINVAL in case a legacy REDIST address
>> is attempted to be set while REDIST_REGIONS were set. This case
>> is discriminated by looking at the count field.
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>>
>> ---
>>
>> v1 -> v2:
>> - simplify the check sequence
>> ---
>>  arch/arm64/kvm/vgic/vgic-mmio-v3.c | 15 +++++++--------
>>  1 file changed, 7 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
>> index 15a6c98ee92f0..013b737b658f8 100644
>> --- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
>> +++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
>> @@ -791,10 +791,6 @@ static int vgic_v3_insert_redist_region(struct kvm *kvm, uint32_t index,
>>  	size_t size = count * KVM_VGIC_V3_REDIST_SIZE;
>>  	int ret;
>>  
>> -	/* single rdist region already set ?*/
>> -	if (!count && !list_empty(rd_regions))
>> -		return -EINVAL;
>> -
>>  	/* cross the end of memory ? */
>>  	if (base + size < base)
>>  		return -EINVAL;
>> @@ -805,11 +801,14 @@ static int vgic_v3_insert_redist_region(struct kvm *kvm, uint32_t index,
>>  	} else {
>>  		rdreg = list_last_entry(rd_regions,
>>  					struct vgic_redist_region, list);
>> -		if (index != rdreg->index + 1)
>> -			return -EINVAL;
>>  
>> -		/* Cannot add an explicitly sized regions after legacy region */
>> -		if (!rdreg->count)
>> +		if ((!count) != (!rdreg->count))
>> +			return -EINVAL; /* Mix REDIST and REDIST_REGION */
> 
> Urgh... The triple negation killed me. Can we come up with a more
> intuitive expression? Something like:

Yes sometimes I can be "different" ;-)
> 
> 		/* Don't mix single region and discrete redist regions */
> 		if (!count && rdreg->count)
> 			return -EINVAL;>
> Does it capture what you want to express?

yes it does!

Thanks

Eric
> 
> Thanks,
> 
> 	M.
> 

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