5 files changed, 142 insertions, 0 deletions
diff --git a/drivers/virt/coco/Kconfig b/drivers/virt/coco/Kconfig
index 87d142c1f932..d9ff676bf48d 100644
--- a/drivers/virt/coco/Kconfig
+++ b/drivers/virt/coco/Kconfig
@@ -9,6 +9,8 @@ config TSM_REPORTS
 
 source "drivers/virt/coco/efi_secret/Kconfig"
 
+source "drivers/virt/coco/pkvm-guest/Kconfig"
+
 source "drivers/virt/coco/sev-guest/Kconfig"
 
 source "drivers/virt/coco/tdx-guest/Kconfig"
diff --git a/drivers/virt/coco/Makefile b/drivers/virt/coco/Makefile
index 18c1aba5edb7..b69c30c1c720 100644
--- a/drivers/virt/coco/Makefile
+++ b/drivers/virt/coco/Makefile
@@ -4,5 +4,6 @@
 #
 obj-$(CONFIG_TSM_REPORTS)	+= tsm.o
 obj-$(CONFIG_EFI_SECRET)	+= efi_secret/
+obj-$(CONFIG_ARM_PKVM_GUEST)	+= pkvm-guest/
 obj-$(CONFIG_SEV_GUEST)		+= sev-guest/
 obj-$(CONFIG_INTEL_TDX_GUEST)	+= tdx-guest/
diff --git a/drivers/virt/coco/pkvm-guest/Kconfig b/drivers/virt/coco/pkvm-guest/Kconfig
new file mode 100644
index 000000000000..d2f344f1f98f
--- /dev/null
+++ b/drivers/virt/coco/pkvm-guest/Kconfig
@@ -0,0 +1,10 @@
+config ARM_PKVM_GUEST
+	bool "Arm pKVM protected guest driver"
+	depends on ARM64
+	help
+	  Protected guests running under the pKVM hypervisor on arm64
+	  are isolated from the host and must issue hypercalls to enable
+	  interaction with virtual devices. This driver implements
+	  support for probing and issuing these hypercalls.
+
+	  If unsure, say 'N'.
diff --git a/drivers/virt/coco/pkvm-guest/Makefile b/drivers/virt/coco/pkvm-guest/Makefile
new file mode 100644
index 000000000000..4bee24579423
--- /dev/null
+++ b/drivers/virt/coco/pkvm-guest/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_ARM_PKVM_GUEST) += arm-pkvm-guest.o
diff --git a/drivers/virt/coco/pkvm-guest/arm-pkvm-guest.c b/drivers/virt/coco/pkvm-guest/arm-pkvm-guest.c
new file mode 100644
index 000000000000..56a3859dda8a
--- /dev/null
+++ b/drivers/virt/coco/pkvm-guest/arm-pkvm-guest.c
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Support for the hypercall interface exposed to protected guests by
+ * pKVM.
+ *
+ * Author: Will Deacon <will@kernel.org>
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include <linux/arm-smccc.h>
+#include <linux/array_size.h>
+#include <linux/io.h>
+#include <linux/mem_encrypt.h>
+#include <linux/mm.h>
+#include <linux/pgtable.h>
+
+#include <asm/hypervisor.h>
+
+static size_t pkvm_granule;
+
+static int arm_smccc_do_one_page(u32 func_id, phys_addr_t phys)
+{
+	phys_addr_t end = phys + PAGE_SIZE;
+
+	while (phys < end) {
+		struct arm_smccc_res res;
+
+		arm_smccc_1_1_invoke(func_id, phys, 0, 0, &res);
+		if (res.a0 != SMCCC_RET_SUCCESS)
+			return -EPERM;
+
+		phys += pkvm_granule;
+	}
+
+	return 0;
+}
+
+static int __set_memory_range(u32 func_id, unsigned long start, int numpages)
+{
+	void *addr = (void *)start, *end = addr + numpages * PAGE_SIZE;
+
+	while (addr < end) {
+		int err;
+
+		err = arm_smccc_do_one_page(func_id, virt_to_phys(addr));
+		if (err)
+			return err;
+
+		addr += PAGE_SIZE;
+	}
+
+	return 0;
+}
+
+static int pkvm_set_memory_encrypted(unsigned long addr, int numpages)
+{
+	return __set_memory_range(ARM_SMCCC_VENDOR_HYP_KVM_MEM_UNSHARE_FUNC_ID,
+				  addr, numpages);
+}
+
+static int pkvm_set_memory_decrypted(unsigned long addr, int numpages)
+{
+	return __set_memory_range(ARM_SMCCC_VENDOR_HYP_KVM_MEM_SHARE_FUNC_ID,
+				  addr, numpages);
+}
+
+static const struct arm64_mem_crypt_ops pkvm_crypt_ops = {
+	.encrypt	= pkvm_set_memory_encrypted,
+	.decrypt	= pkvm_set_memory_decrypted,
+};
+
+static int mmio_guard_ioremap_hook(phys_addr_t phys, size_t size,
+				   pgprot_t *prot)
+{
+	phys_addr_t end;
+	pteval_t protval = pgprot_val(*prot);
+
+	/*
+	 * We only expect MMIO emulation for regions mapped with device
+	 * attributes.
+	 */
+	if (protval != PROT_DEVICE_nGnRE && protval != PROT_DEVICE_nGnRnE)
+		return 0;
+
+	phys = PAGE_ALIGN_DOWN(phys);
+	end = phys + PAGE_ALIGN(size);
+
+	while (phys < end) {
+		const int func_id = ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_FUNC_ID;
+		int err;
+
+		err = arm_smccc_do_one_page(func_id, phys);
+		if (err)
+			return err;
+
+		phys += PAGE_SIZE;
+	}
+
+	return 0;
+}
+
+void pkvm_init_hyp_services(void)
+{
+	int i;
+	struct arm_smccc_res res;
+	const u32 funcs[] = {
+		ARM_SMCCC_KVM_FUNC_HYP_MEMINFO,
+		ARM_SMCCC_KVM_FUNC_MEM_SHARE,
+		ARM_SMCCC_KVM_FUNC_MEM_UNSHARE,
+	};
+
+	for (i = 0; i < ARRAY_SIZE(funcs); ++i) {
+		if (!kvm_arm_hyp_service_available(funcs[i]))
+			return;
+	}
+
+	arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_HYP_MEMINFO_FUNC_ID,
+			     0, 0, 0, &res);
+	if (res.a0 > PAGE_SIZE) /* Includes error codes */
+		return;
+
+	pkvm_granule = res.a0;
+	arm64_mem_crypt_ops_register(&pkvm_crypt_ops);
+
+	if (kvm_arm_hyp_service_available(ARM_SMCCC_KVM_FUNC_MMIO_GUARD))
+		arm64_ioremap_prot_hook_register(&mmio_guard_ioremap_hook);
+}