[PATCH 4/6] RISC-V: Add SBI v0.2 base extension

[Atish Patra]

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 at wdc.com>
---
 arch/riscv/include/asm/kvm_vcpu_sbi.h |  2 +
 arch/riscv/include/asm/sbi.h          |  8 +++
 arch/riscv/kvm/Makefile               |  4 +-
 arch/riscv/kvm/vcpu_sbi.c             |  3 ++
 arch/riscv/kvm/vcpu_sbi_base.c        | 73 +++++++++++++++++++++++++++
 5 files changed, 88 insertions(+), 2 deletions(-)
 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 743c71f0c331..e208c8ac57fe 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 2355515785eb..7d8f2b389253 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -27,6 +27,14 @@ enum sbi_ext_id {
 	SBI_EXT_IPI = 0x735049,
 	SBI_EXT_RFENCE = 0x52464E43,
 	SBI_EXT_HSM = 0x48534D,
+
+	/* 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 8efb78faab5a..a95c91ba9a51 100644
--- a/arch/riscv/kvm/Makefile
+++ b/arch/riscv/kvm/Makefile
@@ -9,6 +9,6 @@ ccflags-y := -Ivirt/kvm -Iarch/riscv/kvm
 kvm-objs := $(common-objs-y)
 
 kvm-objs += main.o vm.o vmid.o tlb.o mmu.o
-kvm-objs += vcpu.o vcpu_exit.o vcpu_switch.o vcpu_timer.o vcpu_sbi.o vcpu_sbi_legacy.o
-
+kvm-objs += vcpu.o vcpu_exit.o vcpu_switch.o vcpu_timer.o
+kvm-objs += vcpu_sbi.o vcpu_sbi_base.o vcpu_sbi_legacy.o
 obj-$(CONFIG_KVM)	+= kvm.o
diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
index 85bb7491c0e0..bb50d63f78e7 100644
--- a/arch/riscv/kvm/vcpu_sbi.c
+++ b/arch/riscv/kvm/vcpu_sbi.c
@@ -31,8 +31,11 @@ static int kvm_linux_err_map_sbi(int err)
 }
 
 extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_legacy;
+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 000000000000..025d0eae50b0
--- /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 at 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 = -ENOTSUPP;
+		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,
+};
-- 
2.24.0