[RFC PATCH v2 24/58] KVM: arm64: iommu: Support DABT for IOMMU

[Mostafa Saleh <smostafa@google.com>]

Soon, SMMUv3 driver would be added and it would need to emulate
access to some of its MMIO space.

Add a handler for DABTs for IOMMU drivers to be able to do so.

Signed-off-by: Mostafa Saleh <smostafa@google.com>
---
 arch/arm64/kvm/hyp/include/nvhe/iommu.h |  2 ++
 arch/arm64/kvm/hyp/nvhe/iommu/iommu.c   | 17 +++++++++++++++++
 arch/arm64/kvm/hyp/nvhe/mem_protect.c   | 19 +++++++++++++++++--
 3 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/hyp/include/nvhe/iommu.h b/arch/arm64/kvm/hyp/include/nvhe/iommu.h
index 06d12b35fa3e..cff75d67d807 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/iommu.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/iommu.h
@@ -21,6 +21,7 @@ size_t kvm_iommu_map_pages(pkvm_handle_t domain_id,
 size_t kvm_iommu_unmap_pages(pkvm_handle_t domain_id, unsigned long iova,
 			     size_t pgsize, size_t pgcount);
 phys_addr_t kvm_iommu_iova_to_phys(pkvm_handle_t domain_id, unsigned long iova);
+bool kvm_iommu_host_dabt_handler(struct kvm_cpu_context *host_ctxt, u64 esr, u64 addr);
 
 /* Flags for memory allocation for IOMMU drivers */
 #define IOMMU_PAGE_NOCACHE				BIT(0)
@@ -49,6 +50,7 @@ struct kvm_iommu_ops {
 	phys_addr_t (*iova_to_phys)(struct kvm_hyp_iommu_domain *domain, unsigned long iova);
 	void (*iotlb_sync)(struct kvm_hyp_iommu_domain *domain,
 			   struct iommu_iotlb_gather *gather);
+	bool (*dabt_handler)(struct kvm_cpu_context *host_ctxt, u64 esr, u64 addr);
 };
 
 int kvm_iommu_init(void);
diff --git a/arch/arm64/kvm/hyp/nvhe/iommu/iommu.c b/arch/arm64/kvm/hyp/nvhe/iommu/iommu.c
index fbab335d3490..e45dadd0c4aa 100644
--- a/arch/arm64/kvm/hyp/nvhe/iommu/iommu.c
+++ b/arch/arm64/kvm/hyp/nvhe/iommu/iommu.c
@@ -4,6 +4,10 @@
  *
  * Copyright (C) 2022 Linaro Ltd.
  */
+#include <asm/kvm_hyp.h>
+
+#include <hyp/adjust_pc.h>
+
 #include <kvm/iommu.h>
 
 #include <nvhe/iommu.h>
@@ -375,6 +379,19 @@ phys_addr_t kvm_iommu_iova_to_phys(pkvm_handle_t domain_id, unsigned long iova)
 	return phys;
 }
 
+bool kvm_iommu_host_dabt_handler(struct kvm_cpu_context *host_ctxt, u64 esr, u64 addr)
+{
+	bool ret = false;
+
+	if (kvm_iommu_ops && kvm_iommu_ops->dabt_handler)
+		ret = kvm_iommu_ops->dabt_handler(host_ctxt, esr, addr);
+
+	if (ret)
+		kvm_skip_host_instr();
+
+	return ret;
+}
+
 static int iommu_power_on(struct kvm_power_domain *pd)
 {
 	struct kvm_hyp_iommu *iommu = container_of(pd, struct kvm_hyp_iommu,
diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index a428ad9ca871..0fae651107db 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -16,6 +16,7 @@
 #include <hyp/fault.h>
 
 #include <nvhe/gfp.h>
+#include <nvhe/iommu.h>
 #include <nvhe/memory.h>
 #include <nvhe/mem_protect.h>
 #include <nvhe/mm.h>
@@ -799,11 +800,16 @@ static int handle_host_perm_fault(struct kvm_cpu_context *host_ctxt, u64 esr, u6
 	return handled ? 0 : -EPERM;
 }
 
+static bool is_dabt(u64 esr)
+{
+	return ESR_ELx_EC(esr) == ESR_ELx_EC_DABT_LOW;
+}
+
 void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt)
 {
 	struct kvm_vcpu_fault_info fault;
 	u64 esr, addr;
-	int ret = 0;
+	int ret = -EPERM;
 
 	esr = read_sysreg_el2(SYS_ESR);
 	if (!__get_fault_info(esr, &fault)) {
@@ -817,7 +823,15 @@ void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt)
 	}
 
 	addr = (fault.hpfar_el2 & HPFAR_MASK) << 8;
-	ret = host_stage2_idmap(addr);
+	addr |= fault.far_el2 & FAR_MASK;
+
+	if (is_dabt(esr) && !addr_is_memory(addr) &&
+	    kvm_iommu_host_dabt_handler(host_ctxt, esr, addr))
+		goto return_to_host;
+
+	/* If not handled, attempt to map the page. */
+	if (ret == -EPERM)
+		ret = host_stage2_idmap(addr);
 
 	if ((esr & ESR_ELx_FSC_TYPE) == ESR_ELx_FSC_PERM)
 		ret = handle_host_perm_fault(host_ctxt, esr, addr);
@@ -827,6 +841,7 @@ void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt)
 	else
 		BUG_ON(ret && ret != -EAGAIN);
 
+return_to_host:
 	trace_host_mem_abort(esr, addr);
 }
 
-- 
2.47.0.338.g60cca15819-goog