RISC-V: KVM: Save mvendorid, marchid, and mimpid when creating VCPU

We should save VCPU mvendorid, marchid, and mimpid at the time
of creating VCPU so that we don't have to do host SBI call every
time Guest/VM ask for these details.
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Anup Patel <anup@brainfault.org>

arch/riscv/include/asm/kvm_host.h

@@ -165,6 +165,11 @@ struct kvm_vcpu_arch {
 	/* ISA feature bits (similar to MISA) */
 	DECLARE_BITMAP(isa, RISCV_ISA_EXT_MAX);
 
+	/* Vendor, Arch, and Implementation details */
+	unsigned long mvendorid;
+	unsigned long marchid;
+	unsigned long mimpid;
+
 	/* SSCRATCH, STVEC, and SCOUNTEREN of Host */
 	unsigned long host_sscratch;
 	unsigned long host_stvec;

arch/riscv/kvm/vcpu.c

@@ -21,6 +21,7 @@
 #include <asm/csr.h>
 #include <asm/cacheflush.h>
 #include <asm/hwcap.h>
+#include <asm/sbi.h>
 
 const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
 	KVM_GENERIC_VCPU_STATS(),
@@ -171,6 +172,11 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
 			set_bit(host_isa, vcpu->arch.isa);
 	}
 
+	/* Setup vendor, arch, and implementation details */
+	vcpu->arch.mvendorid = sbi_get_mvendorid();
+	vcpu->arch.marchid = sbi_get_marchid();
+	vcpu->arch.mimpid = sbi_get_mimpid();
+
 	/* Setup VCPU hfence queue */
 	spin_lock_init(&vcpu->arch.hfence_lock);
 

arch/riscv/kvm/vcpu_sbi_base.c

@@ -19,7 +19,6 @@ static int kvm_sbi_ext_base_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
 {
 	int ret = 0;
 	struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
-	struct sbiret ecall_ret;
 
 	switch (cp->a6) {
 	case SBI_EXT_BASE_GET_SPEC_VERSION:
@@ -48,13 +47,13 @@ static int kvm_sbi_ext_base_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
 			*out_val = kvm_vcpu_sbi_find_ext(cp->a0) ? 1 : 0;
 		break;
 	case SBI_EXT_BASE_GET_MVENDORID:
+		*out_val = vcpu->arch.mvendorid;
+		break;
 	case SBI_EXT_BASE_GET_MARCHID:
+		*out_val = vcpu->arch.marchid;
+		break;
 	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);
+		*out_val = vcpu->arch.mimpid;
 		break;
 	default:
 		ret = -EOPNOTSUPP;