From 373ce9e4663ca88d5e85ea4c08ece6017d281ad6 Mon Sep 17 00:00:00 2001
From: Atish Patra <atish.patra@wdc.com>
Date: Mon, 30 Mar 2020 01:14:22 -0700
Subject: [PATCH] RISC-V: Add SBI v0.2 base extension

SBI v0.2 base extension defined to allow backward compatibility and
probing of future extensions. This is also the only mandatory SBI
extension that must be implemented by SBI implementors.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/include/asm/kvm_vcpu_sbi.h |  2 +
 arch/riscv/include/asm/sbi.h          |  8 +++
 arch/riscv/kvm/Makefile               |  1 +
 arch/riscv/kvm/vcpu_sbi.c             |  3 +-
 arch/riscv/kvm/vcpu_sbi_base.c        | 73 +++++++++++++++++++++++++++
 5 files changed, 86 insertions(+), 1 deletion(-)
 create mode 100644 arch/riscv/kvm/vcpu_sbi_base.c

diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
index 5d33373a7534e7..afd06a8833acf0 100644
--- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
+++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
@@ -9,6 +9,8 @@
 #ifndef __RISCV_KVM_VCPU_SBI_H__
 #define __RISCV_KVM_VCPU_SBI_H__
 
+#define KVM_SBI_IMPID 3
+
 #define KVM_SBI_VERSION_MAJOR 0
 #define KVM_SBI_VERSION_MINOR 2
 
diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index 289621da4a2a8f..20e049857e98a0 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -28,6 +28,14 @@ enum sbi_ext_id {
 	SBI_EXT_RFENCE = 0x52464E43,
 	SBI_EXT_HSM = 0x48534D,
 	SBI_EXT_SRST = 0x53525354,
+
+	/* Experimentals extensions must lie within this range */
+	SBI_EXT_EXPERIMENTAL_START = 0x0800000,
+	SBI_EXT_EXPERIMENTAL_END = 0x08FFFFFF,
+
+	/* Vendor extensions must lie within this range */
+	SBI_EXT_VENDOR_START = 0x09000000,
+	SBI_EXT_VENDOR_END = 0x09FFFFFF,
 };
 
 enum sbi_ext_base_fid {
diff --git a/arch/riscv/kvm/Makefile b/arch/riscv/kvm/Makefile
index 53cbecc44c4c1c..aaf02efafc0fcb 100644
--- a/arch/riscv/kvm/Makefile
+++ b/arch/riscv/kvm/Makefile
@@ -23,4 +23,5 @@ kvm-y += vcpu_exit.o
 kvm-y += vcpu_switch.o
 kvm-y += vcpu_sbi.o
 kvm-$(CONFIG_RISCV_SBI_V01) += vcpu_sbi_legacy.o
+kvm-y += vcpu_sbi_base.o
 kvm-y += vcpu_timer.o
diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
index e51de3e4526a04..5533ffc25ed0d3 100644
--- a/arch/riscv/kvm/vcpu_sbi.c
+++ b/arch/riscv/kvm/vcpu_sbi.c
@@ -39,9 +39,10 @@ static const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_legacy = {
 	.handler = NULL,
 };
 #endif
-
+extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_base;
 static const struct kvm_vcpu_sbi_extension *sbi_ext[] = {
 	&vcpu_sbi_ext_legacy,
+	&vcpu_sbi_ext_base,
 };
 
 void kvm_riscv_vcpu_sbi_forward(struct kvm_vcpu *vcpu, struct kvm_run *run)
diff --git a/arch/riscv/kvm/vcpu_sbi_base.c b/arch/riscv/kvm/vcpu_sbi_base.c
new file mode 100644
index 00000000000000..48f1164f189c03
--- /dev/null
+++ b/arch/riscv/kvm/vcpu_sbi_base.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+/**
+ * Copyright (c) 2020 Western Digital Corporation or its affiliates.
+ *
+ * Authors:
+ *     Atish Patra <atish.patra@wdc.com>
+ */
+
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/kvm_host.h>
+#include <asm/csr.h>
+#include <asm/sbi.h>
+#include <asm/kvm_vcpu_timer.h>
+#include <asm/kvm_vcpu_sbi.h>
+
+static int kvm_sbi_ext_base_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
+				    unsigned long *out_val,
+				    struct kvm_cpu_trap *trap, bool *exit)
+{
+	int ret = 0;
+	struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
+	struct sbiret ecall_ret;
+
+	if (!cp)
+		return -EINVAL;
+
+	switch (cp->a6) {
+	case SBI_EXT_BASE_GET_SPEC_VERSION:
+		*out_val = (KVM_SBI_VERSION_MAJOR <<
+			    SBI_SPEC_VERSION_MAJOR_SHIFT) |
+			    KVM_SBI_VERSION_MINOR;
+		break;
+	case SBI_EXT_BASE_GET_IMP_ID:
+		*out_val = KVM_SBI_IMPID;
+		break;
+	case SBI_EXT_BASE_GET_IMP_VERSION:
+		*out_val = 0;
+		break;
+	case SBI_EXT_BASE_PROBE_EXT:
+		*out_val = kvm_vcpu_sbi_find_ext(cp->a0) ? 1 : 0;
+		if ((!*out_val) &&
+		    ((cp->a0 >= SBI_EXT_EXPERIMENTAL_START &&
+		     cp->a0 <= SBI_EXT_EXPERIMENTAL_END) ||
+		    ((cp->a0 >= SBI_EXT_VENDOR_START &&
+		     cp->a0 <= SBI_EXT_VENDOR_END)))) {
+		/* For experimental/vendor extensions forward to the userspace*/
+			kvm_riscv_vcpu_sbi_forward(vcpu, run);
+			*exit = true;
+		}
+		break;
+	case SBI_EXT_BASE_GET_MVENDORID:
+	case SBI_EXT_BASE_GET_MARCHID:
+	case SBI_EXT_BASE_GET_MIMPID:
+		ecall_ret = sbi_ecall(SBI_EXT_BASE, cp->a6, 0, 0, 0, 0, 0, 0);
+		if (!ecall_ret.error)
+			*out_val = ecall_ret.value;
+		/*TODO: We are unnecessarily converting the error twice */
+		ret = sbi_err_map_linux_errno(ecall_ret.error);
+		break;
+	default:
+		ret = -EOPNOTSUPP;
+		break;
+	}
+
+	return ret;
+}
+
+const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_base = {
+	.extid_start = SBI_EXT_BASE,
+	.extid_end = SBI_EXT_BASE,
+	.handler = kvm_sbi_ext_base_handler,
+};