On 12.01.2023 16:43, Xenia Ragiadakou wrote:
> On 1/12/23 13:49, Xenia Ragiadakou wrote:
>> On 1/12/23 13:31, Jan Beulich wrote:
>>> On 04.01.2023 09:44, Xenia Ragiadakou wrote:
>>>> --- a/xen/include/xen/iommu.h
>>>> +++ b/xen/include/xen/iommu.h
>>>> @@ -74,9 +74,13 @@ extern enum __packed iommu_intremap {
>>>> iommu_intremap_restricted,
>>>> iommu_intremap_full,
>>>> } iommu_intremap;
>>>> -extern bool iommu_igfx, iommu_qinval, iommu_snoop;
>>>> #else
>>>> # define iommu_intremap false
>>>> +#endif
>>>> +
>>>> +#ifdef CONFIG_INTEL_IOMMU
>>>> +extern bool iommu_igfx, iommu_qinval, iommu_snoop;
>>>> +#else
>>>> # define iommu_snoop false
>>>> #endif
>>>
>>> Do these declarations really need touching? In patch 2 you didn't move
>>> amd_iommu_perdev_intremap's either.
>>
>> Ok, I will revert this change (as I did in v2 of patch 2) since it is
>> not needed.
>
> Actually, my patch was altering the current behavior by defining
> iommu_snoop as false when !INTEL_IOMMU.
>
> IIUC, there is no control over snoop behavior when using the AMD iommu.
> Hence, iommu_snoop should evaluate to true for AMD iommu.
> However, when using the INTEL iommu the user can disable it via the
> "iommu" param, right?
That's the intended behavior, yes, but right now we allow the option
to also affect behavior on AMD - perhaps wrongly so, as there's one
use outside of VT-x and VT-d code. But of course the option is
documented to be there for VT-d only, so one can view it as user
error if it's used on a non-VT-d system.
> If that's the case then iommu_snoop needs to be moved from vtd/iommu.c
> to x86/iommu.c and iommu_snoop assignment via iommu param needs to be
> guarded by CONFIG_INTEL_IOMMU.
Or #define to true when !INTEL_IOMMU and keep the variable where it
is.
Jan
