[RFC PATCH v2 17/58] KVM: arm64: iommu: Add {attach, detach}_dev

[Mostafa Saleh <smostafa@google.com>]

Add attach/detach dev operations which are forwarded to the driver.

To avoid racing between alloc/free domain and attach/detach dev,
the refcount is used.

Although, as IOMMU attach/detach are per-IOMMU and would require
some sort of locking, nothing in the IOMMU core code need the lock
so delegate that to the driver to use locks when needed and the
hypervisor only guarantees no races between alloc/free domain.

Also, add a new function kvm_iommu_init_device() to initialise common
fields of the IOMMU struct, which is only the lock at the moment.
The IOMMU core code will need to use the lock next for power
management.

Signed-off-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
---
 arch/arm64/kvm/hyp/include/nvhe/iommu.h | 29 +++++++++++++
 arch/arm64/kvm/hyp/nvhe/iommu/iommu.c   | 56 ++++++++++++++++++++++++-
 include/kvm/iommu.h                     |  8 ++++
 3 files changed, 91 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/hyp/include/nvhe/iommu.h b/arch/arm64/kvm/hyp/include/nvhe/iommu.h
index 8f619f415d1f..d6d7447fbac8 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/iommu.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/iommu.h
@@ -35,10 +35,39 @@ struct kvm_iommu_ops {
 	int (*init)(void);
 	int (*alloc_domain)(struct kvm_hyp_iommu_domain *domain, int type);
 	void (*free_domain)(struct kvm_hyp_iommu_domain *domain);
+	struct kvm_hyp_iommu *(*get_iommu_by_id)(pkvm_handle_t iommu_id);
+	int (*attach_dev)(struct kvm_hyp_iommu *iommu, struct kvm_hyp_iommu_domain *domain,
+			  u32 endpoint_id, u32 pasid, u32 pasid_bits);
+	int (*detach_dev)(struct kvm_hyp_iommu *iommu, struct kvm_hyp_iommu_domain *domain,
+			  u32 endpoint_id, u32 pasid);
 };
 
 int kvm_iommu_init(void);
 
+int kvm_iommu_init_device(struct kvm_hyp_iommu *iommu);
+
+static inline hyp_spinlock_t *kvm_iommu_get_lock(struct kvm_hyp_iommu *iommu)
+{
+	/* See struct kvm_hyp_iommu */
+	BUILD_BUG_ON(sizeof(iommu->lock) != sizeof(hyp_spinlock_t));
+	return (hyp_spinlock_t *)(&iommu->lock);
+}
+
+static inline void kvm_iommu_lock_init(struct kvm_hyp_iommu *iommu)
+{
+	hyp_spin_lock_init(kvm_iommu_get_lock(iommu));
+}
+
+static inline void kvm_iommu_lock(struct kvm_hyp_iommu *iommu)
+{
+	hyp_spin_lock(kvm_iommu_get_lock(iommu));
+}
+
+static inline void kvm_iommu_unlock(struct kvm_hyp_iommu *iommu)
+{
+	hyp_spin_unlock(kvm_iommu_get_lock(iommu));
+}
+
 extern struct hyp_mgt_allocator_ops kvm_iommu_allocator_ops;
 
 #endif /* __ARM64_KVM_NVHE_IOMMU_H__ */
diff --git a/arch/arm64/kvm/hyp/nvhe/iommu/iommu.c b/arch/arm64/kvm/hyp/nvhe/iommu/iommu.c
index ba2aed52a74f..df2dbe4c0121 100644
--- a/arch/arm64/kvm/hyp/nvhe/iommu/iommu.c
+++ b/arch/arm64/kvm/hyp/nvhe/iommu/iommu.c
@@ -127,6 +127,19 @@ handle_to_domain(pkvm_handle_t domain_id)
 	return &domains[domain_id % KVM_IOMMU_DOMAINS_PER_PAGE];
 }
 
+static int domain_get(struct kvm_hyp_iommu_domain *domain)
+{
+	int old = atomic_fetch_inc_acquire(&domain->refs);
+
+	BUG_ON(!old || (old + 1 < 0));
+	return 0;
+}
+
+static void domain_put(struct kvm_hyp_iommu_domain *domain)
+{
+	BUG_ON(!atomic_dec_return_release(&domain->refs));
+}
+
 int kvm_iommu_init(void)
 {
 	int ret;
@@ -210,13 +223,44 @@ int kvm_iommu_free_domain(pkvm_handle_t domain_id)
 int kvm_iommu_attach_dev(pkvm_handle_t iommu_id, pkvm_handle_t domain_id,
 			 u32 endpoint_id, u32 pasid, u32 pasid_bits)
 {
-	return -ENODEV;
+	int ret;
+	struct kvm_hyp_iommu *iommu;
+	struct kvm_hyp_iommu_domain *domain;
+
+	iommu = kvm_iommu_ops->get_iommu_by_id(iommu_id);
+	if (!iommu)
+		return -EINVAL;
+
+	domain = handle_to_domain(domain_id);
+	if (!domain || domain_get(domain))
+		return -EINVAL;
+
+	ret = kvm_iommu_ops->attach_dev(iommu, domain, endpoint_id, pasid, pasid_bits);
+	if (ret)
+		domain_put(domain);
+	return ret;
 }
 
 int kvm_iommu_detach_dev(pkvm_handle_t iommu_id, pkvm_handle_t domain_id,
 			 u32 endpoint_id, u32 pasid)
 {
-	return -ENODEV;
+	int ret;
+	struct kvm_hyp_iommu *iommu;
+	struct kvm_hyp_iommu_domain *domain;
+
+	iommu = kvm_iommu_ops->get_iommu_by_id(iommu_id);
+	if (!iommu)
+		return -EINVAL;
+
+	domain = handle_to_domain(domain_id);
+	if (!domain || atomic_read(&domain->refs) <= 1)
+		return -EINVAL;
+
+	ret = kvm_iommu_ops->detach_dev(iommu, domain, endpoint_id, pasid);
+	if (ret)
+		return ret;
+	domain_put(domain);
+	return ret;
 }
 
 size_t kvm_iommu_map_pages(pkvm_handle_t domain_id,
@@ -236,3 +280,11 @@ phys_addr_t kvm_iommu_iova_to_phys(pkvm_handle_t domain_id, unsigned long iova)
 {
 	return 0;
 }
+
+/* Must be called from the IOMMU driver per IOMMU */
+int kvm_iommu_init_device(struct kvm_hyp_iommu *iommu)
+{
+	kvm_iommu_lock_init(iommu);
+
+	return 0;
+}
diff --git a/include/kvm/iommu.h b/include/kvm/iommu.h
index 10ecaae0f6a3..6ff78d766466 100644
--- a/include/kvm/iommu.h
+++ b/include/kvm/iommu.h
@@ -45,4 +45,12 @@ extern void **kvm_nvhe_sym(kvm_hyp_iommu_domains);
 #define KVM_IOMMU_DOMAINS_ROOT_ORDER_NR	\
 	(1 << get_order(KVM_IOMMU_DOMAINS_ROOT_SIZE))
 
+struct kvm_hyp_iommu {
+#ifdef __KVM_NVHE_HYPERVISOR__
+	hyp_spinlock_t			lock;
+#else
+	u32				unused;
+#endif
+};
+
 #endif /* __KVM_IOMMU_H */
-- 
2.47.0.338.g60cca15819-goog