RISC-V: Add EFI runtime services

This patch adds EFI runtime service support for RISC-V.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
[ardb: - Remove the page check]
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

3 files changed, 155 insertions, 1 deletions

diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile
index 61fd1e8b26fb..4d628081bb2f 100644
--- a/drivers/firmware/efi/Makefile
+++ b/drivers/firmware/efi/Makefile
@@ -35,6 +35,8 @@ fake_map-$(CONFIG_X86)			+= x86_fake_mem.o
 arm-obj-$(CONFIG_EFI)			:= efi-init.o arm-runtime.o
 obj-$(CONFIG_ARM)			+= $(arm-obj-y)
 obj-$(CONFIG_ARM64)			+= $(arm-obj-y)
+riscv-obj-$(CONFIG_EFI)			:= efi-init.o riscv-runtime.o
+obj-$(CONFIG_RISCV)			+= $(riscv-obj-y)
 obj-$(CONFIG_EFI_CAPSULE_LOADER)	+= capsule-loader.o
 obj-$(CONFIG_EFI_EARLYCON)		+= earlycon.o
 obj-$(CONFIG_UEFI_CPER_ARM)		+= cper-arm.o
diff --git a/drivers/firmware/efi/libstub/efi-stub.c b/drivers/firmware/efi/libstub/efi-stub.c
index 311a16802dd6..914a343c7785 100644
--- a/drivers/firmware/efi/libstub/efi-stub.c
+++ b/drivers/firmware/efi/libstub/efi-stub.c
@@ -17,7 +17,10 @@
 
 /*
  * This is the base address at which to start allocating virtual memory ranges
- * for UEFI Runtime Services. This is in the low TTBR0 range so that we can use
+ * for UEFI Runtime Services.
+ *
+ * For ARM/ARM64:
+ * This is in the low TTBR0 range so that we can use
  * any allocation we choose, and eliminate the risk of a conflict after kexec.
  * The value chosen is the largest non-zero power of 2 suitable for this purpose
  * both on 32-bit and 64-bit ARM CPUs, to maximize the likelihood that it can
@@ -25,6 +28,12 @@
  * Since 32-bit ARM could potentially execute with a 1G/3G user/kernel split,
  * map everything below 1 GB. (512 MB is a reasonable upper bound for the
  * entire footprint of the UEFI runtime services memory regions)
+ *
+ * For RISC-V:
+ * There is no specific reason for which, this address (512MB) can't be used
+ * EFI runtime virtual address for RISC-V. It also helps to use EFI runtime
+ * services on both RV32/RV64. Keep the same runtime virtual address for RISC-V
+ * as well to minimize the code churn.
  */
 #define EFI_RT_VIRTUAL_BASE	SZ_512M
 #define EFI_RT_VIRTUAL_SIZE	SZ_512M
diff --git a/drivers/firmware/efi/riscv-runtime.c b/drivers/firmware/efi/riscv-runtime.c
new file mode 100644
index 000000000000..d28e715d2bcc
--- /dev/null
+++ b/drivers/firmware/efi/riscv-runtime.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Extensible Firmware Interface
+ *
+ * Copyright (C) 2020 Western Digital Corporation or its affiliates.
+ *
+ * Based on Extensible Firmware Interface Specification version 2.4
+ * Adapted from drivers/firmware/efi/arm-runtime.c
+ *
+ */
+
+#include <linux/dmi.h>
+#include <linux/efi.h>
+#include <linux/io.h>
+#include <linux/memblock.h>
+#include <linux/mm_types.h>
+#include <linux/preempt.h>
+#include <linux/rbtree.h>
+#include <linux/rwsem.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/pgtable.h>
+
+#include <asm/cacheflush.h>
+#include <asm/efi.h>
+#include <asm/mmu.h>
+#include <asm/pgalloc.h>
+
+static bool __init efi_virtmap_init(void)
+{
+	efi_memory_desc_t *md;
+
+	efi_mm.pgd = pgd_alloc(&efi_mm);
+	mm_init_cpumask(&efi_mm);
+	init_new_context(NULL, &efi_mm);
+
+	for_each_efi_memory_desc(md) {
+		phys_addr_t phys = md->phys_addr;
+		int ret;
+
+		if (!(md->attribute & EFI_MEMORY_RUNTIME))
+			continue;
+		if (md->virt_addr == 0)
+			return false;
+
+		ret = efi_create_mapping(&efi_mm, md);
+		if (ret) {
+			pr_warn("  EFI remap %pa: failed to create mapping (%d)\n",
+				&phys, ret);
+			return false;
+		}
+	}
+
+	if (efi_memattr_apply_permissions(&efi_mm, efi_set_mapping_permissions))
+		return false;
+
+	return true;
+}
+
+/*
+ * Enable the UEFI Runtime Services if all prerequisites are in place, i.e.,
+ * non-early mapping of the UEFI system table and virtual mappings for all
+ * EFI_MEMORY_RUNTIME regions.
+ */
+static int __init riscv_enable_runtime_services(void)
+{
+	u64 mapsize;
+
+	if (!efi_enabled(EFI_BOOT)) {
+		pr_info("EFI services will not be available.\n");
+		return 0;
+	}
+
+	efi_memmap_unmap();
+
+	mapsize = efi.memmap.desc_size * efi.memmap.nr_map;
+
+	if (efi_memmap_init_late(efi.memmap.phys_map, mapsize)) {
+		pr_err("Failed to remap EFI memory map\n");
+		return 0;
+	}
+
+	if (efi_soft_reserve_enabled()) {
+		efi_memory_desc_t *md;
+
+		for_each_efi_memory_desc(md) {
+			int md_size = md->num_pages << EFI_PAGE_SHIFT;
+			struct resource *res;
+
+			if (!(md->attribute & EFI_MEMORY_SP))
+				continue;
+
+			res = kzalloc(sizeof(*res), GFP_KERNEL);
+			if (WARN_ON(!res))
+				break;
+
+			res->start	= md->phys_addr;
+			res->end	= md->phys_addr + md_size - 1;
+			res->name	= "Soft Reserved";
+			res->flags	= IORESOURCE_MEM;
+			res->desc	= IORES_DESC_SOFT_RESERVED;
+
+			insert_resource(&iomem_resource, res);
+		}
+	}
+
+	if (efi_runtime_disabled()) {
+		pr_info("EFI runtime services will be disabled.\n");
+		return 0;
+	}
+
+	if (efi_enabled(EFI_RUNTIME_SERVICES)) {
+		pr_info("EFI runtime services access via paravirt.\n");
+		return 0;
+	}
+
+	pr_info("Remapping and enabling EFI services.\n");
+
+	if (!efi_virtmap_init()) {
+		pr_err("UEFI virtual mapping missing or invalid -- runtime services will not be available\n");
+		return -ENOMEM;
+	}
+
+	/* Set up runtime services function pointers */
+	efi_native_runtime_setup();
+	set_bit(EFI_RUNTIME_SERVICES, &efi.flags);
+
+	return 0;
+}
+early_initcall(riscv_enable_runtime_services);
+
+void efi_virtmap_load(void)
+{
+	preempt_disable();
+	switch_mm(current->active_mm, &efi_mm, NULL);
+}
+
+void efi_virtmap_unload(void)
+{
+	switch_mm(&efi_mm, current->active_mm, NULL);
+	preempt_enable();
+}