Re: [PATCH 10/18] iommu/vt-d: Add custom allocator for IOASID

Alex Williamson
2019-04-15T20:37:16Z

On Mon, 8 Apr 2019 16:59:25 -0700
Jacob Pan <jacob.jun.pan@linux.intel.com> wrote:

> When VT-d driver runs in the guest, PASID allocation must be
> performed via virtual command interface. This patch register a
> custom IOASID allocator which takes precedence over the default
> IDR based allocator. The resulting IOASID allocation will always
> come from the host. This ensures that PASID namespace is system-
> wide.
>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> Signed-off-by: Liu, Yi L <yi.l.liu@intel.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> ---
> drivers/iommu/intel-iommu.c | 50 +++++++++++++++++++++++++++++++++++++++++++++
> include/linux/intel-iommu.h | 1 +
> 2 files changed, 51 insertions(+)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 28cb713..a38d774 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -4820,6 +4820,42 @@ static int __init platform_optin_force_iommu(void)
> return 1;
> }
>
> +static ioasid_t intel_ioasid_alloc(ioasid_t min, ioasid_t max, void *data)
> +{
> + struct intel_iommu *iommu = data;
> + ioasid_t ioasid;
> +
> + if (vcmd_alloc_pasid(iommu, &ioasid))
> + return INVALID_IOASID;
> + return ioasid;

How does this honor min/max?

> +}
> +
> +static int intel_ioasid_free(ioasid_t ioasid, void *data)
> +{
> + struct iommu_pasid_alloc_info *svm;
> + struct intel_iommu *iommu = data;
> +
> + if (!iommu || !cap_caching_mode(iommu->cap))
> + return -EINVAL;
> + /*
> + * Sanity check the ioasid owner is done at upper layer, e.g. VFIO
> + * We can only free the PASID when all the devices are unbond.
> + */
> + svm = ioasid_find(NULL, ioasid, NULL);
> + if (!svm) {
> + pr_warn("Freeing unbond IOASID %d\n", ioasid);
> + return -EBUSY;
> + }
> + vcmd_free_pasid(iommu, ioasid);
> +
> + return 0;
> +}
> +
> +static struct ioasid_allocator intel_iommu_ioasid_allocator = {
> + .alloc = intel_ioasid_alloc,
> + .free = intel_ioasid_free,
> +};
> +
> int __init intel_iommu_init(void)
> {
> int ret = -ENODEV;
> @@ -4921,6 +4957,20 @@ int __init intel_iommu_init(void)
> "%s", iommu->name);
> iommu_device_set_ops(&iommu->iommu, &intel_iommu_ops);
> iommu_device_register(&iommu->iommu);
> + if (cap_caching_mode(iommu->cap) && sm_supported(iommu)) {
> + /*
> + * Register a custom ASID allocator if we are running
> + * in a guest, the purpose is to have a system wide PASID
> + * namespace among all PASID users.
> + * Note that only one vIOMMU in each guest is supported.

Why one vIOMMU per guest? This would prevent guests with multiple PCI
domains aiui.

> + */
> + intel_iommu_ioasid_allocator.pdata = (void *)iommu;
> + ret = ioasid_set_allocator(&intel_iommu_ioasid_allocator);
> + if (ret == -EBUSY) {
> + pr_info("Custom IOASID allocator already registered\n");
> + break;
> + }
> + }
> }
>
> bus_set_iommu(&pci_bus_type, &intel_iommu_ops);
> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
> index b29c85c..bc09d80 100644
> --- a/include/linux/intel-iommu.h
> +++ b/include/linux/intel-iommu.h
> @@ -31,6 +31,7 @@
> #include <linux/iommu.h>
> #include <linux/io-64-nonatomic-lo-hi.h>
> #include <linux/dmar.h>
> +#include <linux/ioasid.h>
>
> #include <asm/cacheflush.h>
> #include <asm/iommu.h>