[PATCH 2/6] RISC-V: Mark the existing SBI v0.1 implementation as legacy

[Atish Patra]

The existing SBI specification impelementation follows v0.1 or legacy
specification. The latest specification known as v0.2 allows more
scalability and performance improvements.

Rename the existing implementation as legacy and provide a way to allow
future extensions.

Signed-off-by: Atish Patra <atish.patra@xxxxxxx>
---
 arch/riscv/include/asm/kvm_vcpu_sbi.h |  29 +++++
 arch/riscv/kvm/vcpu_sbi.c             | 149 ++++++++++++++++++++------
 2 files changed, 148 insertions(+), 30 deletions(-)
 create mode 100644 arch/riscv/include/asm/kvm_vcpu_sbi.h

diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
new file mode 100644
index 000000000000..5b3523a01bce
--- /dev/null
+++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/**
+ * Copyright (c) 2020 Western Digital Corporation or its affiliates.
+ *
+ * Authors:
+ *     Atish Patra <atish.patra@xxxxxxx>
+ */
+
+#ifndef __RISCV_KVM_VCPU_SBI_H__
+#define __RISCV_KVM_VCPU_SBI_H__
+
+#define KVM_SBI_VERSION_MAJOR 0
+#define KVM_SBI_VERSION_MINOR 2
+
+struct kvm_vcpu_sbi_extension {
+	unsigned long extid_start;
+	unsigned long extid_end;
+	/**
+	 * SBI extension handler. It can be defined for a given extension or group of
+	 * extension. But it should always return linux error codes rather than SBI
+	 * specific error codes.
+	 */
+	int (*handler)(struct kvm_vcpu *vcpu, struct kvm_run *run,
+		       unsigned long *out_val, struct kvm_cpu_trap *utrap,
+		       bool *exit);
+};
+
+const struct kvm_vcpu_sbi_extension *kvm_vcpu_sbi_find_ext(unsigned long extid);
+#endif /* __RISCV_KVM_VCPU_SBI_H__ */
diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
index 9d1d25cf217f..efddac5362a9 100644
--- a/arch/riscv/kvm/vcpu_sbi.c
+++ b/arch/riscv/kvm/vcpu_sbi.c
@@ -12,9 +12,25 @@
 #include <asm/csr.h>
 #include <asm/sbi.h>
 #include <asm/kvm_vcpu_timer.h>
+#include <asm/kvm_vcpu_sbi.h>
 
-#define SBI_VERSION_MAJOR			0
-#define SBI_VERSION_MINOR			1
+static int kvm_linux_err_map_sbi(int err)
+{
+	switch (err) {
+	case 0:
+		return SBI_SUCCESS;
+	case -EPERM:
+		return SBI_ERR_DENIED;
+	case -EINVAL:
+		return SBI_ERR_INVALID_PARAM;
+	case -EFAULT:
+		return SBI_ERR_INVALID_ADDRESS;
+	case -ENOTSUPP:
+		return SBI_ERR_NOT_SUPPORTED;
+	default:
+		return SBI_ERR_FAILURE;
+	};
+}
 
 static void kvm_sbi_system_shutdown(struct kvm_vcpu *vcpu,
 				    struct kvm_run *run, u32 type)
@@ -70,16 +86,17 @@ int kvm_riscv_vcpu_sbi_return(struct kvm_vcpu *vcpu, struct kvm_run *run)
 	return 0;
 }
 
-int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run)
+static int kvm_sbi_ext_legacy_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
+				      unsigned long *out_val,
+				      struct kvm_cpu_trap *utrap,
+				      bool *exit)
 {
 	ulong hmask;
-	int i, ret = 1;
+	int i, ret = 0;
 	u64 next_cycle;
 	struct kvm_vcpu *rvcpu;
-	bool next_sepc = true;
 	struct cpumask cm, hm;
 	struct kvm *kvm = vcpu->kvm;
-	struct kvm_cpu_trap utrap = { 0 };
 	struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
 
 	if (!cp)
@@ -93,8 +110,7 @@ int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run)
 		 * handled in kernel so we forward these to user-space
 		 */
 		kvm_riscv_vcpu_sbi_forward(vcpu, run);
-		next_sepc = false;
-		ret = 0;
+		*exit = true;
 		break;
 	case SBI_EXT_0_1_SET_TIMER:
 #if __riscv_xlen == 32
@@ -102,47 +118,42 @@ int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run)
 #else
 		next_cycle = (u64)cp->a0;
 #endif
-		kvm_riscv_vcpu_timer_next_event(vcpu, next_cycle);
+		ret = kvm_riscv_vcpu_timer_next_event(vcpu, next_cycle);
 		break;
 	case SBI_EXT_0_1_CLEAR_IPI:
-		kvm_riscv_vcpu_unset_interrupt(vcpu, IRQ_VS_SOFT);
+		ret = kvm_riscv_vcpu_unset_interrupt(vcpu, IRQ_VS_SOFT);
 		break;
 	case SBI_EXT_0_1_SEND_IPI:
 		if (cp->a0)
 			hmask = kvm_riscv_vcpu_unpriv_read(vcpu, false, cp->a0,
-							   &utrap);
+							   utrap);
 		else
 			hmask = (1UL << atomic_read(&kvm->online_vcpus)) - 1;
-		if (utrap.scause) {
-			utrap.sepc = cp->sepc;
-			kvm_riscv_vcpu_trap_redirect(vcpu, &utrap);
-			next_sepc = false;
+		if (utrap->scause)
 			break;
-		}
+
 		for_each_set_bit(i, &hmask, BITS_PER_LONG) {
 			rvcpu = kvm_get_vcpu_by_id(vcpu->kvm, i);
-			kvm_riscv_vcpu_set_interrupt(rvcpu, IRQ_VS_SOFT);
+			ret = kvm_riscv_vcpu_set_interrupt(rvcpu, IRQ_VS_SOFT);
+			if (ret < 0)
+				break;
 		}
 		break;
 	case SBI_EXT_0_1_SHUTDOWN:
 		kvm_sbi_system_shutdown(vcpu, run, KVM_SYSTEM_EVENT_SHUTDOWN);
-		next_sepc = false;
-		ret = 0;
+		*exit = true;
 		break;
 	case SBI_EXT_0_1_REMOTE_FENCE_I:
 	case SBI_EXT_0_1_REMOTE_SFENCE_VMA:
 	case SBI_EXT_0_1_REMOTE_SFENCE_VMA_ASID:
 		if (cp->a0)
 			hmask = kvm_riscv_vcpu_unpriv_read(vcpu, false, cp->a0,
-							   &utrap);
+							   utrap);
 		else
 			hmask = (1UL << atomic_read(&kvm->online_vcpus)) - 1;
-		if (utrap.scause) {
-			utrap.sepc = cp->sepc;
-			kvm_riscv_vcpu_trap_redirect(vcpu, &utrap);
-			next_sepc = false;
+		if (utrap->scause)
 			break;
-		}
+
 		cpumask_clear(&cm);
 		for_each_set_bit(i, &hmask, BITS_PER_LONG) {
 			rvcpu = kvm_get_vcpu_by_id(vcpu->kvm, i);
@@ -152,22 +163,100 @@ int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run)
 		}
 		riscv_cpuid_to_hartid_mask(&cm, &hm);
 		if (cp->a7 == SBI_EXT_0_1_REMOTE_FENCE_I)
-			sbi_remote_fence_i(cpumask_bits(&hm));
+			ret = sbi_remote_fence_i(cpumask_bits(&hm));
 		else if (cp->a7 == SBI_EXT_0_1_REMOTE_SFENCE_VMA)
-			sbi_remote_hfence_vvma(cpumask_bits(&hm),
+			ret = sbi_remote_hfence_vvma(cpumask_bits(&hm),
 						cp->a1, cp->a2);
 		else
-			sbi_remote_hfence_vvma_asid(cpumask_bits(&hm),
+			ret = sbi_remote_hfence_vvma_asid(cpumask_bits(&hm),
 						cp->a1, cp->a2, cp->a3);
 		break;
 	default:
-		/* Return error for unsupported SBI calls */
-		cp->a0 = SBI_ERR_NOT_SUPPORTED;
+		ret = -EINVAL;
 		break;
 	};
 
+	return ret;
+}
+
+const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_legacy = {
+	.extid_start = SBI_EXT_0_1_SET_TIMER,
+	.extid_end = SBI_EXT_0_1_SHUTDOWN,
+	.handler = kvm_sbi_ext_legacy_handler,
+};
+
+static const struct kvm_vcpu_sbi_extension *sbi_ext[] = {
+	&vcpu_sbi_ext_legacy,
+};
+
+const struct kvm_vcpu_sbi_extension *kvm_vcpu_sbi_find_ext(unsigned long extid)
+{
+	int i = 0;
+
+	for (i = 0; i < ARRAY_SIZE(sbi_ext); i++) {
+		if (sbi_ext[i]->extid_start <= extid &&
+		    sbi_ext[i]->extid_end >= extid)
+			return sbi_ext[i];
+	}
+
+	return NULL;
+}
+
+int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run)
+{
+	int ret = 1;
+	bool next_sepc = true;
+	bool userspace_exit = false;
+	struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
+	const struct kvm_vcpu_sbi_extension *sbi_ext;
+	struct kvm_cpu_trap utrap = { 0 };
+	unsigned long out_val = 0;
+	bool ext_is_v01 = false;
+
+	if (!cp)
+		return -EINVAL;
+
+	sbi_ext = kvm_vcpu_sbi_find_ext(cp->a7);
+	if (sbi_ext && sbi_ext->handler) {
+		if (cp->a7 >= SBI_EXT_0_1_SET_TIMER &&
+		    cp->a7 <= SBI_EXT_0_1_SHUTDOWN)
+			ext_is_v01 = true;
+		ret = sbi_ext->handler(vcpu, run, &out_val, &utrap, &userspace_exit);
+	} else {
+		/* Return error for unsupported SBI calls */
+		cp->a0 = SBI_ERR_NOT_SUPPORTED;
+		goto ecall_done;
+	}
+
+	/* Handle special error cases i.e trap, exit or userspace forward */
+	if (utrap.scause) {
+		/* No need to increment sepc or exit ioctl loop */
+		ret = 1;
+		utrap.sepc = cp->sepc;
+		kvm_riscv_vcpu_trap_redirect(vcpu, &utrap);
+		next_sepc = false;
+		goto ecall_done;
+	}
+
+	/* Exit ioctl loop or Propagate the error code the guest */
+	if (userspace_exit) {
+		next_sepc = false;
+		ret = 0;
+	} else {
+		/**
+		 * SBI extension handler always returns an Linux error code. Convert
+		 * it to the SBI specific error code that can be propagated the SBI
+		 * caller.
+		 */
+		ret = kvm_linux_err_map_sbi(ret);
+		cp->a0 = ret;
+		ret = 1;
+	}
+ecall_done:
 	if (next_sepc)
 		cp->sepc += 4;
+	if (!ext_is_v01)
+		cp->a1 = out_val;
 
 	return ret;
 }
-- 
2.24.0