On Fri, Mar 10, 2023 at 07:39:00AM +0000, Liu, Yi L wrote:
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From: Nicolin Chen nicolinc@nvidia.com Sent: Friday, March 10, 2023 3:10 PM
On Fri, Mar 10, 2023 at 11:30:04AM +0800, Baolu Lu wrote:
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On 3/9/23 4:09 PM, Yi Liu wrote:
This provides a way for userspace to probe the supported hwpt data types by kernel. Currently, kernel only supports
IOMMU_HWPT_TYPE_DEFAULT,
new types would be added per vendor drivers' extension.
Userspace that wants to allocate hw_pagetable with user data should
check
this. While for the allocation without user data, no need for it. It is supported by default.
Co-developed-by: Nicolin Chen nicolinc@nvidia.com Signed-off-by: Nicolin Chen nicolinc@nvidia.com Signed-off-by: Yi Liu yi.l.liu@intel.com
drivers/iommu/iommufd/device.c | 1 + drivers/iommu/iommufd/hw_pagetable.c | 18 +++++++++++++++--- drivers/iommu/iommufd/iommufd_private.h | 2 ++ drivers/iommu/iommufd/main.c | 2 +- include/uapi/linux/iommufd.h | 8 ++++++++ 5 files changed, 27 insertions(+), 4 deletions(-)
diff --git a/drivers/iommu/iommufd/device.c
b/drivers/iommu/iommufd/device.c
index 19cd6df46c6a..0328071dcac1 100644 --- a/drivers/iommu/iommufd/device.c +++ b/drivers/iommu/iommufd/device.c @@ -322,6 +322,7 @@ int iommufd_device_get_hw_info(struct
iommufd_ucmd *ucmd)
cmd->out_data_type = ops->driver_type; cmd->data_len = length;
cmd->out_hwpt_type_bitmap =iommufd_hwpt_type_bitmaps[ops->driver_type];
rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));diff --git a/drivers/iommu/iommufd/hw_pagetable.c
b/drivers/iommu/iommufd/hw_pagetable.c
index 67facca98de1..160712256c64 100644 --- a/drivers/iommu/iommufd/hw_pagetable.c +++ b/drivers/iommu/iommufd/hw_pagetable.c @@ -173,6 +173,14 @@ static const size_t
iommufd_hwpt_alloc_data_size[] = {
[IOMMU_HWPT_TYPE_DEFAULT] = 0,};
+/*
- bitmaps of supported hwpt types of by underlying iommu, indexed
- by ops->driver_type which is one of enum iommu_hw_info_type.
- */
+const u64 iommufd_hwpt_type_bitmaps[] = {
[IOMMU_HW_INFO_TYPE_DEFAULT] =BIT_ULL(IOMMU_HWPT_TYPE_DEFAULT),
+};
I am a bit confused here. Why do you need this array? What I read is that you want to convert ops->driver_type to a bit position in cmd->out_hwpt_type_bitmap.
Am I getting it right?
If so, why not just cmd->out_hwpt_type_bitmap = BIT_ULL(ops->driver_type);
?
The reason is for future extensions. If future usages need different types of user data to allocate hwpt, it can define a new type and corresponding data structure. Such new usages may be using new vendor-specific page tables or vendor-agnostic usages like Re-use of the KVM page table in the IOMMU mentioned by IOMMUFD basic series.
https://lore.kernel.org/kvm/0-v6-a196d26f289e+11787-iommufd_jgg@nvidia.com/
A driver_type would be IOMMUFD_HW_INFO_TYPExx. What's inside the BIT_ULL is IOMMUFD_HWPT_TYPE_*. It seems to get a bit confusing after several rounds of renaming though. And they do seem to be a bit of duplications at the actual values, at least for now.
For now, vendor drivers only have one stage-1 page table format. But in the future, it may change per new page table format introduction and new usage.
Yea, that's what I thought too. Yet, I am wondering a bit if it'd be better to have an ops->hwpt_type in the drivers, v.s. maintaining a potentially big chunk of the array here.
Thanks Nic