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SubjectRE: [PATCH v8 04/11] iommu: Add sva iommu_domain support
Date
> From: Baolu Lu
> Sent: Friday, June 10, 2022 3:16 PM
> >
> >> +#define __IOMMU_DOMAIN_HOST_VA (1U << 5) /* Host CPU virtual
> address */
> >
> > Do you mean general CPU VA? or Host CPU VA, I'm reading the latter as
> 2nd
> > stage?
>
> Host CPU VA. In the near future, we will add another flag _GUEST_VA, so
> that the shared page table types are distiguished.

How does the kernel knows that an user page table translates guest VA?
IMHO I don't think the kernel should care about it except managing
all the aspects related to the user page table itself...

>
> >
> >> +
> >> /*
> >> * This are the possible domain-types
> >> *
> >> @@ -86,15 +89,24 @@ struct iommu_domain_geometry {
> >> #define IOMMU_DOMAIN_DMA_FQ
> (__IOMMU_DOMAIN_PAGING | \
> >> __IOMMU_DOMAIN_DMA_API | \
> >> __IOMMU_DOMAIN_DMA_FQ)
> >> +#define IOMMU_DOMAIN_SVA (__IOMMU_DOMAIN_SHARED |
> \
> >> + __IOMMU_DOMAIN_HOST_VA)
> >
> > Doesn't shared automatically mean CPU VA? Do we need another flag?
>
> Yes. Shared means CPU VA, but there're many types. Besides above two, we
> also see the shared KVM/EPT.
>

Will the two sharing scenarios share any common code? If not then
having a separate flag bit is meaningless.

It might be more straightforward to be:

#define IOMMU_DOMAIN_SVA __IOMMU_DOMAIN_SVA
#define IOMMU_DOMAIN_KVM __IOMMU_DOMAIN_KVM
#define IOMMU_DOMAIN_USER __IOMMU_DOMAIN_USER

Thanks
Kevin

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