Re: [PATCH] amd iommu: disable iommu emulation on non-iommu systems

[Wei Wang <wei.wang2@amd.com>]

On 02/01/2012 04:58 PM, Jan Beulich wrote:
>>>> On 26.01.12 at 11:56, Wei Wang<wei.wang2@amd.com>  wrote:
>> --- a/xen/drivers/passthrough/amd/iommu_guest.c	Tue Jan 24 16:46:17 2012 +0000
>> +++ b/xen/drivers/passthrough/amd/iommu_guest.c	Thu Jan 26 11:50:02 2012 +0100
>> @@ -805,6 +805,9 @@ int guest_iommu_set_base(struct domain *
>>      p2m_type_t t;
>>      struct guest_iommu *iommu = domain_iommu(d);
>>
>> +    if ( !is_hvm_domain(d) || !iommu_enabled || !iommuv2_enabled )
>> +        return 0;
>
> Is it really appropriate/correct to return 0 here, while ...


good point, will be fixed in the next try. No one use 
guest_iommu_set_base so far until remaining patches got committed.

>> +
>>      if ( !iommu )
>>          return -EACCES;

>
> ... here it is -EACCES? Further, are the extra checks needed at all
> (i.e. wouldn't domain_iommu() return NULL in all of these cases
> anyway due to the same checks being added to guest_iommu_init())?
> If so, the checks you add to guest_iommu_destroy() are pointless
> too.

It is just to make sure those functions are not called by an unexpected 
code path since it is non-static. But I can remove it if you prefer that.


Thanks,
Wei

> Jan
>
>