[PATCH v2 04/13] KVM: Parse the device tree and register the ITS region with pKVM

[Sebastian Ene <sebastianene@google.com>]

Identify the ITS base address from the device tree and store it in the
pkvm_protected_regs array so that it will be unmapped from the host
address space.
Register a callback to forward all the MMIO requests to the device to
prevent breaking ITS functionality in this patch. The patch by itself
shouldn't break any existing functionality even though all the accesses
from the gic-ITS driver are now mediated inside pKVM.

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 | 37 +++++++++++++++++++
 arch/arm64/kvm/pkvm.c                 | 52 +++++++++++++++++++++++++++
 4 files changed, 93 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 0a471564be00..370225f0e72c 100644
--- a/arch/arm64/include/asm/kvm_pkvm.h
+++ b/arch/arm64/include/asm/kvm_pkvm.h
@@ -31,6 +31,8 @@ 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(its_emulate_forward_req)(struct pkvm_protected_reg *region, u64 offset,
+						  bool write, u64 *reg, u8 reg_size);
 
 int pkvm_init_host_vm(struct kvm *kvm, unsigned long type);
 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 f57450ebcb49..70fbca325852 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 \
 	 ../hyp-entry.o ../exception.o ../pgtable.o ../vgic-v5-sr.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..63a42f520ed2
--- /dev/null
+++ b/arch/arm64/kvm/hyp/nvhe/its_emulate.c
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <asm/kvm_pkvm.h>
+#include <nvhe/mem_protect.h>
+
+void its_emulate_forward_req(struct pkvm_protected_reg *region, u64 offset, bool write, u64 *reg,
+			     u8 reg_size)
+{
+	void __iomem *addr = __hyp_va(PFN_PHYS(region->pfn) + offset);
+
+	switch (reg_size) {
+	case 1:
+		if (!write)
+			*reg = readb_relaxed(addr);
+		else
+			writeb_relaxed(*reg, addr);
+		break;
+	case 2:
+		if (!write)
+			*reg = readw_relaxed(addr);
+		else
+			writew_relaxed(*reg, addr);
+		break;
+	case 4:
+		if (!write)
+			*reg = readl_relaxed(addr);
+		else
+			writel_relaxed(*reg, addr);
+		break;
+	case 8:
+		if (!write)
+			*reg = readq_relaxed(addr);
+		else
+			writeq_relaxed(*reg, addr);
+		break;
+	}
+}
diff --git a/arch/arm64/kvm/pkvm.c b/arch/arm64/kvm/pkvm.c
index 428723b1b0f5..4bfffbedac4c 100644
--- a/arch/arm64/kvm/pkvm.c
+++ b/arch/arm64/kvm/pkvm.c
@@ -9,8 +9,13 @@
 #include <linux/kmemleak.h>
 #include <linux/kvm_host.h>
 #include <asm/kvm_mmu.h>
+#include <asm/kvm_pkvm.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 <linux/irqchip/arm-gic-v3.h>
 
 #include <asm/kvm_pkvm.h>
 
@@ -39,6 +44,47 @@ static int __init register_memblock_regions(void)
 	return 0;
 }
 
+static int __init register_its_emulated_region(void)
+{
+	struct device_node *np;
+	struct resource res;
+	int i = 0;
+	int ret;
+
+	for_each_compatible_node(np, NULL, "arm,gic-v3-its") {
+		ret = of_address_to_resource(np, 0, &res);
+		if (ret)
+			goto out_fail;
+
+		if (i >= PKVM_PROTECTED_REGS_NUM) {
+			kvm_err("Out of protected region slots\n");
+			ret = -ENOSPC;
+			goto out_fail;
+		}
+
+		/*
+		 * Note: don't unmap the entire animal from the host because devices need
+		 * to be able to access GITS_TRANSLATER to raise MSIs. If the
+		 * page where GITS_TRANSLATER is given to HYP, devices won't be
+		 * able to map it in their IOMMU when the IOMMU is managed by
+		 * pKVM.
+		 */
+		kvm_nvhe_sym(pkvm_protected_regs)[i].pfn = PHYS_PFN(res.start);
+		kvm_nvhe_sym(pkvm_protected_regs)[i].cb =
+			lm_alias(&kvm_nvhe_sym(its_emulate_forward_req));
+		kvm_nvhe_sym(pkvm_protected_regs)[i].nr_pages =
+			PFN_DOWN(min_t(u64, resource_size(&res), PAGE_ALIGN_DOWN(GITS_TRANSLATER)));
+
+		i++;
+	}
+
+	kvm_nvhe_sym(num_protected_reg) = i;
+	return 0;
+out_fail:
+	of_node_put(np);
+	return ret;
+}
+
 void __init kvm_hyp_reserve(void)
 {
 	u64 hyp_mem_pages = 0;
@@ -57,6 +103,12 @@ void __init kvm_hyp_reserve(void)
 		return;
 	}
 
+	ret = register_its_emulated_region();
+	if (ret) {
+		kvm_err("Failed to register ITS region %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();
-- 
2.55.0.654.g21b8a5bc05-goog