Subject: [PATCH v6 14/25] iommu/arm-smmu-v3-kvm: Add MMIO emulation

From: Mostafa Saleh <[email-masked]>
Date: Fri, 1 May 2026 11:19:16 +0000

Add data abort handler for the SMMUs, at the moment most registers
are just passthrough.
In the next patches CMDQ/STE emulation will be added which inserts
logic to some register access.

Signed-off-by: Mostafa Saleh <[email-masked]>
---
 .../iommu/arm/arm-smmu-v3/pkvm/arm-smmu-v3.c  | 143 ++++++++++++++++++
 .../iommu/arm/arm-smmu-v3/pkvm/arm_smmu_v3.h  |  10 ++
 2 files changed, 153 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu-v3/pkvm/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/pkvm/arm-smmu-v3.c
index d9945db9e102..cce5a51b4656 100644
--- a/drivers/iommu/arm/arm-smmu-v3/pkvm/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/pkvm/arm-smmu-v3.c
@@ -8,6 +8,7 @@
 
 #include <nvhe/iommu.h>
 #include <nvhe/mem_protect.h>
+#include <nvhe/trap_handler.h>
 
 #include "arm_smmu_v3.h"
 #include "../arm-smmu-v3.h"
@@ -106,6 +107,7 @@ static int smmu_init_device(struct hyp_arm_smmu_v3_device *smmu)
 	if (!PAGE_ALIGNED(smmu->mmio_addr | smmu->mmio_size))
 		return -EINVAL;
 
+	hyp_spin_lock_init(&smmu->lock);
 	ret = __pkvm_host_donate_hyp_mmio(smmu->mmio_addr, smmu->mmio_size, &haddr);
 	if (ret)
 		return ret;
@@ -144,6 +146,8 @@ static int smmu_init(void)
 			goto out_reclaim_smmu;
 	}
 
+	BUILD_BUG_ON(sizeof(hyp_spinlock_t) != sizeof(u32));
+
 	return 0;
 
 out_reclaim_smmu:
@@ -153,6 +157,144 @@ static int smmu_init(void)
 	return ret;
 }
 
+static bool smmu_dabt_device(struct hyp_arm_smmu_v3_device *smmu,
+			     struct user_pt_regs *regs,
+			     u64 esr, u32 off)
+{
+	bool is_write = esr & ESR_ELx_WNR;
+	unsigned int len = BIT((esr & ESR_ELx_SAS) >> ESR_ELx_SAS_SHIFT);
+	int rd = (esr & ESR_ELx_SRT_MASK) >> ESR_ELx_SRT_SHIFT;
+	const u64 read_write = -1ULL;
+	const u64 no_access = 0;
+	u64 mask = no_access;
+	const u64 read_only = is_write ? no_access : read_write;
+	bool is_xzr = (rd == 31);
+	u64 val = is_xzr ? 0 : regs->regs[rd];
+
+	switch (off) {
+	case ARM_SMMU_IDR0:
+		if (len != sizeof(u32))
+			break;
+		/* Clear stage-2 support, hide MSI to avoid write back to cmdq */
+		mask = read_only & ~(IDR0_S2P | IDR0_VMID16 | IDR0_MSI | IDR0_HYP);
+		break;
+	/* Passthrough the register access for bisectiblity, handled later */
+	case ARM_SMMU_CMDQ_BASE:
+	case ARM_SMMU_CMDQ_PROD:
+	case ARM_SMMU_CMDQ_CONS:
+	case ARM_SMMU_STRTAB_BASE:
+	case ARM_SMMU_STRTAB_BASE_CFG:
+	case ARM_SMMU_GBPA:
+		mask = read_write;
+		break;
+	case ARM_SMMU_CR0:
+		if (len != sizeof(u32))
+			break;
+		mask = read_write;
+		break;
+	case ARM_SMMU_CR1: {
+		/* Based on Linux implementation */
+		u64 cr1_template = FIELD_PREP(CR1_TABLE_SH, ARM_SMMU_SH_ISH) |
+				FIELD_PREP(CR1_TABLE_OC, CR1_CACHE_WB) |
+				FIELD_PREP(CR1_TABLE_IC, CR1_CACHE_WB) |
+				FIELD_PREP(CR1_QUEUE_SH, ARM_SMMU_SH_ISH) |
+				FIELD_PREP(CR1_QUEUE_OC, CR1_CACHE_WB) |
+				FIELD_PREP(CR1_QUEUE_IC, CR1_CACHE_WB);
+		if (len != sizeof(u32))
+			break;
+		/* Don't mess with shareability/cacheability. */
+		if (is_write) {
+			WARN_ON(val != cr1_template);
+			val = cr1_template;
+		}
+		mask = read_write;
+		break;
+	}
+
+	/* Allowed 32 bit registers. */
+	case ARM_SMMU_EVTQ_PROD + SZ_64K:
+	case ARM_SMMU_EVTQ_CONS + SZ_64K:
+	case ARM_SMMU_EVTQ_IRQ_CFG1:
+	case ARM_SMMU_EVTQ_IRQ_CFG2:
+	case ARM_SMMU_PRIQ_PROD + SZ_64K:
+	case ARM_SMMU_PRIQ_CONS + SZ_64K:
+	case ARM_SMMU_PRIQ_IRQ_CFG1:
+	case ARM_SMMU_PRIQ_IRQ_CFG2:
+	case ARM_SMMU_GERRORN:
+	case ARM_SMMU_GERROR_IRQ_CFG1:
+	case ARM_SMMU_GERROR_IRQ_CFG2:
+	case ARM_SMMU_IRQ_CTRLACK:
+	case ARM_SMMU_IRQ_CTRL:
+	case ARM_SMMU_CR0ACK:
+	case ARM_SMMU_CR2:
+		if (len != sizeof(u32))
+			break;
+		mask = read_write;
+		break;
+	/* Allowed 64 bit registers. */
+	case ARM_SMMU_EVTQ_BASE:
+	case ARM_SMMU_EVTQ_IRQ_CFG0:
+	case ARM_SMMU_PRIQ_BASE:
+	case ARM_SMMU_PRIQ_IRQ_CFG0:
+	case ARM_SMMU_GERROR_IRQ_CFG0:
+		if (len != sizeof(u64))
+			break;
+		mask = read_write;
+		break;
+	/* Allowed RO 32 bit registers. */
+	case ARM_SMMU_IIDR:
+	case ARM_SMMU_IDR5:
+	case ARM_SMMU_IDR3:
+	case ARM_SMMU_IDR1:
+	case ARM_SMMU_GERROR:
+		if (len != sizeof(u32))
+			break;
+		mask = read_only;
+	};
+
+	if (WARN_ON(!mask))
+		goto out_ret;
+
+	if (is_write) {
+		if (len == sizeof(u64))
+			writeq_relaxed(val & mask, smmu->base + off);
+		else
+			writel_relaxed(val & mask, smmu->base + off);
+
+		return true;
+	}
+
+	if (len == sizeof(u64))
+		val = readq_relaxed(smmu->base + off) & mask;
+	else
+		val = readl_relaxed(smmu->base + off) & mask;
+	/*
+	 * Device might be read senstive, so do it but ignore writing
+	 * back for xzr.
+	 */
+	if (!is_xzr)
+		regs->regs[rd] = val;
+
+out_ret:
+	return true;
+}
+
+static bool smmu_dabt_handler(struct user_pt_regs *regs, u64 esr, u64 addr)
+{
+	struct hyp_arm_smmu_v3_device *smmu;
+	bool ret;
+
+	for_each_smmu(smmu) {
+		if (addr < smmu->mmio_addr || addr >= smmu->mmio_addr + smmu->mmio_size)
+			continue;
+		hyp_spin_lock(&smmu->lock);
+		ret = smmu_dabt_device(smmu, regs, esr, addr - smmu->mmio_addr);
+		hyp_spin_unlock(&smmu->lock);
+		return ret;
+	}
+	return false;
+}
+
 static int smmu_host_stage2_idmap(phys_addr_t start, phys_addr_t end, int prot)
 {
 	return 0;
@@ -162,4 +304,5 @@ static int smmu_host_stage2_idmap(phys_addr_t start, phys_addr_t end, int prot)
 struct kvm_iommu_ops smmu_ops = {
 	.init				= smmu_init,
 	.host_stage2_idmap		= smmu_host_stage2_idmap,
+	.dabt_handler			= smmu_dabt_handler,
 };
diff --git a/drivers/iommu/arm/arm-smmu-v3/pkvm/arm_smmu_v3.h b/drivers/iommu/arm/arm-smmu-v3/pkvm/arm_smmu_v3.h
index 82b84673e85b..263b0fef262d 100644
--- a/drivers/iommu/arm/arm-smmu-v3/pkvm/arm_smmu_v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/pkvm/arm_smmu_v3.h
@@ -4,6 +4,10 @@
 
 #include <asm/kvm_asm.h>
 
+#ifdef __KVM_NVHE_HYPERVISOR__
+#include <nvhe/spinlock.h>
+#endif
+
 /*
  * Parameters from the trusted host:
  * @mmio_addr		base address of the SMMU registers
@@ -15,6 +19,7 @@
  * @oas			PA size
  * @pgsize_bitmap	Supported page sizes
  * @sid_bits		Max number of SID bits supported
+ * @lock		Lock to protect SMMU
  */
 struct hyp_arm_smmu_v3_device {
 	phys_addr_t		mmio_addr;
@@ -24,6 +29,11 @@ struct hyp_arm_smmu_v3_device {
 	unsigned long		oas;
 	unsigned long		pgsize_bitmap;
 	unsigned int		sid_bits;
+#ifdef __KVM_NVHE_HYPERVISOR__
+	hyp_spinlock_t		lock;
+#else
+	u32			lock;
+#endif
 };
 
 extern size_t kvm_nvhe_sym(kvm_hyp_arm_smmu_v3_count);
-- 
2.54.0.545.g6539524ca2-goog