[PATCH 04/14] KVM: arm64: Mediate host access to GIC/ITS MMIO via unmapping

[Sebastian Ene <sebastianene@google.com>]

Unmap the ITS MMIO region from the host address space to enforce
hypervisor mediation.
Identify the ITS base address from the device tree and store it in a
protected region. A callback is registered to handle host accesses to
this region; currently, the handler simply forwards all MMIO requests
to the physical hardware. This provides the infrastructure for future
hardware state validation without changing current behavior.

Signed-off-by: Sebastian Ene <sebastianene@google.com>
---
 arch/arm64/include/asm/kvm_pkvm.h     |  2 ++
 arch/arm64/kvm/hyp/nvhe/Makefile      |  3 ++-
 arch/arm64/kvm/hyp/nvhe/its_emulate.c | 23 ++++++++++++++++
 arch/arm64/kvm/pkvm.c                 | 38 +++++++++++++++++++++++++++
 4 files changed, 65 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm64/kvm/hyp/nvhe/its_emulate.c

diff --git a/arch/arm64/include/asm/kvm_pkvm.h b/arch/arm64/include/asm/kvm_pkvm.h
index 5321ced2f50a..ef00c1bf7d00 100644
--- a/arch/arm64/include/asm/kvm_pkvm.h
+++ b/arch/arm64/include/asm/kvm_pkvm.h
@@ -32,6 +32,8 @@ struct pkvm_protected_reg {
 
 extern struct pkvm_protected_reg kvm_nvhe_sym(pkvm_protected_regs)[];
 extern unsigned int kvm_nvhe_sym(num_protected_reg);
+extern void kvm_nvhe_sym(pkvm_handle_forward_req)(struct pkvm_protected_reg *region, u64 offset,
+						  bool write, u64 *reg, u8 reg_size);
 
 int pkvm_init_host_vm(struct kvm *kvm);
 int pkvm_create_hyp_vm(struct kvm *kvm);
diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile
index a244ec25f8c5..eb43269fbac2 100644
--- a/arch/arm64/kvm/hyp/nvhe/Makefile
+++ b/arch/arm64/kvm/hyp/nvhe/Makefile
@@ -24,7 +24,8 @@ CFLAGS_switch.nvhe.o += -Wno-override-init
 
 hyp-obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o \
 	 hyp-main.o hyp-smp.o psci-relay.o early_alloc.o page_alloc.o \
-	 cache.o setup.o mm.o mem_protect.o sys_regs.o pkvm.o stacktrace.o ffa.o
+	 cache.o setup.o mm.o mem_protect.o sys_regs.o pkvm.o stacktrace.o ffa.o \
+	 its_emulate.o
 hyp-obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \
 	 ../fpsimd.o ../hyp-entry.o ../exception.o ../pgtable.o
 hyp-obj-y += ../../../kernel/smccc-call.o
diff --git a/arch/arm64/kvm/hyp/nvhe/its_emulate.c b/arch/arm64/kvm/hyp/nvhe/its_emulate.c
new file mode 100644
index 000000000000..0eecbb011898
--- /dev/null
+++ b/arch/arm64/kvm/hyp/nvhe/its_emulate.c
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <asm/kvm_pkvm.h>
+#include <nvhe/mem_protect.h>
+
+
+void pkvm_handle_forward_req(struct pkvm_protected_reg *region, u64 offset, bool write,
+			     u64 *reg, u8 reg_size)
+{
+	void __iomem *addr = __hyp_va((region->start_pfn << PAGE_SHIFT) + offset);
+
+	if (reg_size == sizeof(u32)) {
+		if (!write)
+			*reg = readl_relaxed(addr);
+		else
+			writel_relaxed(*reg, addr);
+	} else if (reg_size == sizeof(u64)) {
+		if (!write)
+			*reg = readq_relaxed(addr);
+		else
+			writeq_relaxed(*reg, addr);
+	}
+}
diff --git a/arch/arm64/kvm/pkvm.c b/arch/arm64/kvm/pkvm.c
index d7a0f69a9982..a766be6de735 100644
--- a/arch/arm64/kvm/pkvm.c
+++ b/arch/arm64/kvm/pkvm.c
@@ -11,6 +11,9 @@
 #include <asm/kvm_mmu.h>
 #include <linux/memblock.h>
 #include <linux/mutex.h>
+#include <linux/of_address.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/platform_device.h>
 
 #include <asm/kvm_pkvm.h>
 
@@ -18,6 +21,7 @@
 
 DEFINE_STATIC_KEY_FALSE(kvm_protected_mode_initialized);
 
+static struct pkvm_protected_reg *pkvm_protected_regs = kvm_nvhe_sym(pkvm_protected_regs);
 static struct memblock_region *hyp_memory = kvm_nvhe_sym(hyp_memory);
 static unsigned int *hyp_memblock_nr_ptr = &kvm_nvhe_sym(hyp_memblock_nr);
 
@@ -39,6 +43,34 @@ static int __init register_memblock_regions(void)
 	return 0;
 }
 
+static int __init register_protected_regions(void)
+{
+	int i = 0, ret;
+	struct device_node *np;
+	struct resource res;
+
+	for_each_compatible_node(np, NULL, "arm,gic-v3-its") {
+		ret = of_address_to_resource(np, i, &res);
+		if (ret)
+			return ret;
+
+		if (i >= PKVM_PROTECTED_REGS_NUM)
+			return -ENOMEM;
+
+		if (!PAGE_ALIGNED(res.start) || !PAGE_ALIGNED(resource_size(&res)))
+			return -EINVAL;
+
+		pkvm_protected_regs[i].start_pfn = res.start >> PAGE_SHIFT;
+		pkvm_protected_regs[i].num_pages = resource_size(&res) >> PAGE_SHIFT;
+		pkvm_protected_regs[i].cb = lm_alias(&kvm_nvhe_sym(pkvm_handle_forward_req));
+		i++;
+	}
+
+	kvm_nvhe_sym(num_protected_reg) = i;
+
+	return 0;
+}
+
 void __init kvm_hyp_reserve(void)
 {
 	u64 hyp_mem_pages = 0;
@@ -57,6 +89,12 @@ void __init kvm_hyp_reserve(void)
 		return;
 	}
 
+	ret = register_protected_regions();
+	if (ret) {
+		kvm_err("Failed to register protected reg: %d\n", ret);
+		return;
+	}
+
 	hyp_mem_pages += hyp_s1_pgtable_pages();
 	hyp_mem_pages += host_s2_pgtable_pages();
 	hyp_mem_pages += hyp_vm_table_pages();
-- 
2.53.0.473.g4a7958ca14-goog