[PATCH 1/3] RISC-V: KVM: Disable SBI extension when its probe fails

[Andrew Jones]

When an SBI extension specific probe function exists and fails, then
use the extension_disabled context to disable the extension. This
ensures the extension's functions cannot be invoked. Doing the
disabling in kvm_vcpu_sbi_find_ext() allows it to be done lazily
on its first use. Checking extension_disabled prior to probing
ensures the probe is only executed once for disabled extensions.
Later patches ensure we only execute probe once for enabled
extensions as well.

Signed-off-by: Andrew Jones <ajones at ventanamicro.com>
---
 arch/riscv/kvm/vcpu_sbi.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
index e52fde504433..aa3c126d2e3c 100644
--- a/arch/riscv/kvm/vcpu_sbi.c
+++ b/arch/riscv/kvm/vcpu_sbi.c
@@ -307,18 +307,25 @@ int kvm_riscv_vcpu_get_reg_sbi_ext(struct kvm_vcpu *vcpu,
 const struct kvm_vcpu_sbi_extension *kvm_vcpu_sbi_find_ext(
 				struct kvm_vcpu *vcpu, unsigned long extid)
 {
-	int i;
-	const struct kvm_riscv_sbi_extension_entry *sext;
 	struct kvm_vcpu_sbi_context *scontext = &vcpu->arch.sbi_context;
+	const struct kvm_riscv_sbi_extension_entry *entry;
+	const struct kvm_vcpu_sbi_extension *ext;
+	int i;
 
 	for (i = 0; i < ARRAY_SIZE(sbi_ext); i++) {
-		sext = &sbi_ext[i];
-		if (sext->ext_ptr->extid_start <= extid &&
-		    sext->ext_ptr->extid_end >= extid) {
-			if (sext->dis_idx < KVM_RISCV_SBI_EXT_MAX &&
-			    scontext->extension_disabled[sext->dis_idx])
+		entry = &sbi_ext[i];
+		ext = entry->ext_ptr;
+
+		if (ext->extid_start <= extid && ext->extid_end >= extid) {
+			if (entry->dis_idx >= KVM_RISCV_SBI_EXT_MAX)
+				return ext;
+			if (scontext->extension_disabled[entry->dis_idx])
+				return NULL;
+			if (ext->probe && !ext->probe(vcpu)) {
+				scontext->extension_disabled[entry->dis_idx] = true;
 				return NULL;
-			return sbi_ext[i].ext_ptr;
+			}
+			return ext;
 		}
 	}
 
-- 
2.39.2