[PATCH v4 12/28] KVM: arm64: iommu: Support DABT for IOMMU

Mostafa Saleh
2025-08-19T21:52:37Z

SMMUv3 driver need to trap and emulate access to the MMIO space as
part of the nested implementation.

Add a handler for DABTs for IOMMU drivers to be able to do so, in
case the host fault in page, check if it's part of IOMMU emulation
first.

Signed-off-by: Mostafa Saleh <smostafa@google.com>
---
arch/arm64/include/asm/kvm_arm.h | 2 ++
arch/arm64/kvm/hyp/include/nvhe/iommu.h | 3 ++-
arch/arm64/kvm/hyp/nvhe/iommu/iommu.c | 15 +++++++++++++++
arch/arm64/kvm/hyp/nvhe/mem_protect.c | 10 ++++++++++
4 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index 1da290aeedce..8d63308ccd5c 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -331,6 +331,8 @@

/* Hyp Prefetch Fault Address Register (HPFAR/HDFAR) */
#define HPFAR_MASK (~UL(0xf))
+
+#define FAR_MASK GENMASK_ULL(11, 0)
/*
* We have
* PAR [PA_Shift - 1 : 12] = PA [PA_Shift - 1 : 12]
diff --git a/arch/arm64/kvm/hyp/include/nvhe/iommu.h b/arch/arm64/kvm/hyp/include/nvhe/iommu.h
index 9f4906c6dcc9..10fe4fbf7424 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/iommu.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/iommu.h
@@ -8,6 +8,7 @@
struct kvm_iommu_ops {
int (*init)(void);
void (*host_stage2_idmap)(phys_addr_t start, phys_addr_t end, int prot);
+ bool (*dabt_handler)(struct user_pt_regs *regs, u64 esr, u64 addr);
};

int kvm_iommu_init(void *pool_base, size_t nr_pages);
@@ -16,5 +17,5 @@ void kvm_iommu_host_stage2_idmap(phys_addr_t start, phys_addr_t end,
enum kvm_pgtable_prot prot);
void *kvm_iommu_donate_pages(u8 order);
void kvm_iommu_reclaim_pages(void *ptr);
-
+bool kvm_iommu_host_dabt_handler(struct user_pt_regs *regs, u64 esr, u64 addr);
#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 1673165c7330..376b30f557a2 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 <linux/iommu.h>

#include <nvhe/iommu.h>
@@ -113,3 +117,14 @@ void kvm_iommu_reclaim_pages(void *ptr)
{
hyp_put_page(&iommu_pages_pool, ptr);
}
+
+bool kvm_iommu_host_dabt_handler(struct user_pt_regs *regs, u64 esr, u64 addr)
+{
+ if (kvm_iommu_ops && kvm_iommu_ops->dabt_handler &&
+ kvm_iommu_ops->dabt_handler(regs, esr, addr)) {
+ /* DABT handled by the driver, skip to next instruction. */
+ kvm_skip_host_instr();
+ return true;
+ }
+ return false;
+}
diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index bce6690f29c0..7371b2183e1e 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -595,6 +595,11 @@ static int host_stage2_idmap(u64 addr)
return ret;
}

+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;
@@ -617,6 +622,11 @@ void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt)
*/
BUG_ON(!(fault.hpfar_el2 & HPFAR_EL2_NS));
addr = FIELD_GET(HPFAR_EL2_FIPA, fault.hpfar_el2) << 12;
+ addr |= fault.far_el2 & FAR_MASK;
+
+ if (is_dabt(esr) && !addr_is_memory(addr) &&
+ kvm_iommu_host_dabt_handler(&host_ctxt->regs, esr, addr))
+ return;

ret = host_stage2_idmap(addr);
BUG_ON(ret && ret != -EAGAIN);
--
2.51.0.rc1.167.g924127e9c0-goog