On Fri, Feb 10, 2023 at 03:44:10PM -0700, Alex Williamson wrote:
On Wed, 8 Feb 2023 20:16:38 -0800 Yi Liu yi.l.liu@intel.com wrote:
From: Lu Baolu baolu.lu@linux.intel.com
To support nested translation in the userspace, it should check the underlying hardware information for the capabilities.
Add intel_iommu_hw_info() to report cap_reg and ecap_reg information.
Signed-off-by: Lu Baolu baolu.lu@linux.intel.com Signed-off-by: Yi Liu yi.l.liu@intel.com Signed-off-by: Nicolin Chen nicolinc@nvidia.com Signed-off-by: Yi Sun yi.y.sun@linux.intel.com
drivers/iommu/intel/iommu.c | 19 +++++++++++++++++++ drivers/iommu/intel/iommu.h | 1 + include/uapi/linux/iommufd.h | 21 +++++++++++++++++++++ 3 files changed, 41 insertions(+)
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c index 59df7e42fd53..929f600cc350 100644 --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -4760,8 +4760,26 @@ static void intel_iommu_remove_dev_pasid(struct device *dev, ioasid_t pasid) intel_pasid_tear_down_entry(iommu, dev, pasid, false); } +static void *intel_iommu_hw_info(struct device *dev, u32 *length) +{
- struct device_domain_info *info = dev_iommu_priv_get(dev);
- struct intel_iommu *iommu = info->iommu;
- struct iommu_device_info_vtd *vtd;
- vtd = kzalloc(sizeof(*vtd), GFP_KERNEL);
- if (!vtd)
return ERR_PTR(-ENOMEM);- vtd->cap_reg = iommu->cap;
- vtd->ecap_reg = iommu->ecap;
Just a friendly reminder that these registers are already exposed to userspace under /sys/class/iommu/ and each device has an iommu link back to their iommu device there.
I think in cases of mdevs w/ PASID (eg SIOV) it is not general to get from vfio sysfs to the sysfs path for the iommu.
This series doesn't really stand on its own without some discussion of why that interface is not sufficient for this use case.
IMHO I don't really like the idea of mixing iommufd with sysfs, it should stand on its own.
In particular there is no generic way to go from a iommufd dev_id to any sysfs path, userspace would need prior unique knowledge about the subsystem that is being bound to iommufd first.
So, I think some of those explanations would be good in the commit message?
I would also add explanation about what userspace is supposed to do with these bits when it operates the nesting feature.
Jason