KVM/riscv fixes for 5.18, take #2

- Remove 's' & 'u' as valid ISA extension
 
  - Restrict the extensions that can be disabled
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Merge tag 'kvm-riscv-fixes-5.18-2' of https://github.com/kvm-riscv/linux into HEAD

KVM/riscv fixes for 5.18, take #2

- Remove 's' & 'u' as valid ISA extension

- Do not allow disabling the base extensions 'i'/'m'/'a'/'c'

arch/riscv/kvm/vcpu.c

@@ -38,14 +38,16 @@ const struct kvm_stats_header kvm_vcpu_stats_header = {
 		       sizeof(kvm_vcpu_stats_desc),
 };
 
-#define KVM_RISCV_ISA_ALLOWED	(riscv_isa_extension_mask(a) | \
-				 riscv_isa_extension_mask(c) | \
-				 riscv_isa_extension_mask(d) | \
-				 riscv_isa_extension_mask(f) | \
-				 riscv_isa_extension_mask(i) | \
-				 riscv_isa_extension_mask(m) | \
-				 riscv_isa_extension_mask(s) | \
-				 riscv_isa_extension_mask(u))
+#define KVM_RISCV_ISA_DISABLE_ALLOWED	(riscv_isa_extension_mask(d) | \
+					riscv_isa_extension_mask(f))
+
+#define KVM_RISCV_ISA_DISABLE_NOT_ALLOWED	(riscv_isa_extension_mask(a) | \
+						riscv_isa_extension_mask(c) | \
+						riscv_isa_extension_mask(i) | \
+						riscv_isa_extension_mask(m))
+
+#define KVM_RISCV_ISA_ALLOWED (KVM_RISCV_ISA_DISABLE_ALLOWED | \
+			       KVM_RISCV_ISA_DISABLE_NOT_ALLOWED)
 
 static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)
 {
@@ -219,7 +221,8 @@ static int kvm_riscv_vcpu_set_reg_config(struct kvm_vcpu *vcpu,
 	switch (reg_num) {
 	case KVM_REG_RISCV_CONFIG_REG(isa):
 		if (!vcpu->arch.ran_atleast_once) {
-			vcpu->arch.isa = reg_val;
+			/* Ignore the disable request for these extensions */
+			vcpu->arch.isa = reg_val | KVM_RISCV_ISA_DISABLE_NOT_ALLOWED;
 			vcpu->arch.isa &= riscv_isa_extension_base(NULL);
 			vcpu->arch.isa &= KVM_RISCV_ISA_ALLOWED;
 			kvm_riscv_vcpu_fp_reset(vcpu);