linux-kernel - [PATCH 02/17] iommu: Add nested domain support

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Date:   Wed,  8 Feb 2023 20:31:38 -0800
From:   Yi Liu <yi.l.liu@...el.com>
To:     joro@...tes.org, alex.williamson@...hat.com, jgg@...dia.com,
        kevin.tian@...el.com, robin.murphy@....com
Cc:     cohuck@...hat.com, eric.auger@...hat.com, nicolinc@...dia.com,
        kvm@...r.kernel.org, mjrosato@...ux.ibm.com,
        chao.p.peng@...ux.intel.com, yi.l.liu@...el.com,
        yi.y.sun@...ux.intel.com, peterx@...hat.com, jasowang@...hat.com,
        shameerali.kolothum.thodi@...wei.com, lulu@...hat.com,
        suravee.suthikulpanit@....com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        baolu.lu@...ux.intel.com
Subject: [PATCH 02/17] iommu: Add nested domain support

From: Lu Baolu <baolu.lu@...ux.intel.com>

Introduce a new domain type for a user space I/O address, which is nested
on top of another user space address represented by a UNMANAGED domain. The
mappings of a nested domain are managed by user space software, therefore
it's unnecessary to have map/unmap callbacks. But the updates of the PTEs
in the nested domain page table must be propagated to the caches on both
IOMMU (IOTLB) and devices (DevTLB).

The nested domain is allocated by the domain_alloc_user op, and attached
to the device through the existing iommu_attach_device/group() interfaces.

An new domain op, named iotlb_sync_user is added for the userspace to flush
the hardware caches for a nested domain through iommufd. No wrapper for it
as it's only supposed to be used by iommufd.

Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
Signed-off-by: Yi Liu <yi.l.liu@...el.com>
---
 include/linux/iommu.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 214e3eb9bc86..f6db50f85a20 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -67,6 +67,9 @@ struct iommu_domain_geometry {
 
 #define __IOMMU_DOMAIN_SVA	(1U << 4)  /* Shared process address space */
 
+#define __IOMMU_DOMAIN_NESTED	(1U << 5)  /* User-managed IOVA nested on
+					      a stage-2 translation        */
+
 /*
  * This are the possible domain-types
  *
@@ -92,6 +95,7 @@ struct iommu_domain_geometry {
 				 __IOMMU_DOMAIN_DMA_API |	\
 				 __IOMMU_DOMAIN_DMA_FQ)
 #define IOMMU_DOMAIN_SVA	(__IOMMU_DOMAIN_SVA)
+#define IOMMU_DOMAIN_NESTED	(__IOMMU_DOMAIN_NESTED)
 
 struct iommu_domain {
 	unsigned type;
@@ -321,6 +325,7 @@ struct iommu_ops {
  * @iotlb_sync_map: Sync mappings created recently using @map to the hardware
  * @iotlb_sync: Flush all queued ranges from the hardware TLBs and empty flush
  *            queue
+ * @iotlb_sync_user: Flush hardware TLBs caching user space IO mappings
  * @iova_to_phys: translate iova to physical address
  * @enforce_cache_coherency: Prevent any kind of DMA from bypassing IOMMU_CACHE,
  *                           including no-snoop TLPs on PCIe or other platform
@@ -350,6 +355,8 @@ struct iommu_domain_ops {
 			       size_t size);
 	void (*iotlb_sync)(struct iommu_domain *domain,
 			   struct iommu_iotlb_gather *iotlb_gather);
+	void (*iotlb_sync_user)(struct iommu_domain *domain,
+				void *user_data);
 
 	phys_addr_t (*iova_to_phys)(struct iommu_domain *domain,
 				    dma_addr_t iova);
-- 
2.34.1