From: Nicolin Chen nicolinc@nvidia.com Sent: Wednesday, September 11, 2024 3:21 PM
On Wed, Sep 11, 2024 at 06:25:16AM +0000, Tian, Kevin wrote:
From: Jason Gunthorpe jgg@nvidia.com Sent: Friday, September 6, 2024 2:22 AM
On Thu, Sep 05, 2024 at 11:00:49AM -0700, Nicolin Chen wrote:
On Thu, Sep 05, 2024 at 01:20:39PM -0300, Jason Gunthorpe wrote:
On Tue, Aug 27, 2024 at 09:59:54AM -0700, Nicolin Chen wrote:
+static int arm_smmu_viommu_cache_invalidate(struct
iommufd_viommu *viommu,
struct iommu_user_data_array*array)
+{
struct iommu_domain *domain =iommufd_viommu_to_parent_domain(viommu);
return __arm_smmu_cache_invalidate_user(to_smmu_domain(domain), viommu, array);I'd like to have the viommu struct directly hold the VMID. The nested parent should be sharable between multiple viommus, it doesn't
make
any sense that it would hold the vmid.
This is struggling because it is trying too hard to not have the driver allocate the viommu, and I think we should just go ahead and
do
that. Store the vmid, today copied from the nesting parent in the vmid private struct. No need for iommufd_viommu_to_parent_domain(),
just
rework the APIs to pass the vmid down not a domain.
OK. When I designed all this stuff, we still haven't made mind about sharing the s2 domain, i.e. moving the VMID, which might need a couple of more patches to achieve.
Yes, many more patches, and don't try to do it now.. But we can copy the vmid from the s2 and place it in the viommu struct during allocation time.
does it assume that a viommu object cannot span multiple physical IOMMUs so there is only one vmid per viommu?
I think so. One the reasons of introducing vIOMMU is to maintain the shareability across physical IOMMUs at the s2 HWPT_PAGING.
I don't quite get it. e.g. for intel-iommu the S2 domain itself can be shared across physical IOMMUs then what is the problem preventing a vIOMMU object using that S2 to span multiple IOMMUs?
Probably there is a good reason e.g. for simplification or better aligned with hw accel stuff. But it's not explained clearly so far.