[PATCH v2 6/7] RISC-V: KVM: Add support for control-flow integrity FWFT features

[Inochi Amaoto]

Control-flow integrity is controlled through a WARL field in henvcfg.
Expose the feature only if the Zicfilp/Zicfiss is supported for VS-mode.
Allow the VMM to block access to the feature by disabling the ISA
extension in the guest.

Assisted-by: YuanSheng:claude-4.7-opus
Co-developed-by: Quan Zhou <zhouquan at iscas.ac.cn>
Signed-off-by: Quan Zhou <zhouquan at iscas.ac.cn>
Signed-off-by: Inochi Amaoto <inochiama at gmail.com>
---
 arch/riscv/kvm/vcpu_sbi_fwft.c | 70 ++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)

diff --git a/arch/riscv/kvm/vcpu_sbi_fwft.c b/arch/riscv/kvm/vcpu_sbi_fwft.c
index 375269e43c13..278eb95b97de 100644
--- a/arch/riscv/kvm/vcpu_sbi_fwft.c
+++ b/arch/riscv/kvm/vcpu_sbi_fwft.c
@@ -163,6 +163,58 @@ static long kvm_sbi_fwft_get_misaligned_delegation(struct kvm_vcpu *vcpu,
 	return SBI_SUCCESS;
 }
 
+static bool kvm_sbi_fwft_landing_pad_supported(struct kvm_vcpu *vcpu)
+{
+	return riscv_isa_extension_available(vcpu->arch.isa, ZICFILP);
+}
+
+static void kvm_sbi_fwft_reset_landing_pad(struct kvm_vcpu *vcpu)
+{
+	kvm_sbi_fwft_env_flag_reset_helper(vcpu, ENVCFG_LPE);
+}
+
+static long kvm_sbi_fwft_set_landing_pad(struct kvm_vcpu *vcpu,
+					 struct kvm_sbi_fwft_config *conf,
+					 bool one_reg_access, unsigned long value)
+{
+	return kvm_sbi_fwft_env_flag_set_helper(vcpu, conf, one_reg_access,
+						value, ENVCFG_LPE);
+}
+
+static long kvm_sbi_fwft_get_landing_pad(struct kvm_vcpu *vcpu,
+					 struct kvm_sbi_fwft_config *conf,
+					 bool one_reg_access, unsigned long *value)
+{
+	return kvm_sbi_fwft_env_flag_get_helper(vcpu, conf, one_reg_access,
+						value, ENVCFG_LPE);
+}
+
+static bool kvm_sbi_fwft_shadow_stack_supported(struct kvm_vcpu *vcpu)
+{
+	return riscv_isa_extension_available(vcpu->arch.isa, ZICFISS);
+}
+
+static void kvm_sbi_fwft_reset_shadow_stack(struct kvm_vcpu *vcpu)
+{
+	kvm_sbi_fwft_env_flag_reset_helper(vcpu, ENVCFG_SSE);
+}
+
+static long kvm_sbi_fwft_set_shadow_stack(struct kvm_vcpu *vcpu,
+					  struct kvm_sbi_fwft_config *conf,
+					  bool one_reg_access, unsigned long value)
+{
+	return kvm_sbi_fwft_env_flag_set_helper(vcpu, conf, one_reg_access,
+						value, ENVCFG_SSE);
+}
+
+static long kvm_sbi_fwft_get_shadow_stack(struct kvm_vcpu *vcpu,
+					  struct kvm_sbi_fwft_config *conf,
+					  bool one_reg_access, unsigned long *value)
+{
+	return kvm_sbi_fwft_env_flag_get_helper(vcpu, conf, one_reg_access,
+						value, ENVCFG_SSE);
+}
+
 static bool kvm_sbi_fwft_pte_ad_hw_updating_supported(struct kvm_vcpu *vcpu)
 {
 	return riscv_isa_extension_available(vcpu->arch.isa, SVADU) &&
@@ -288,6 +340,24 @@ static const struct kvm_sbi_fwft_feature features[] = {
 		.set = kvm_sbi_fwft_set_misaligned_delegation,
 		.get = kvm_sbi_fwft_get_misaligned_delegation,
 	},
+	{
+		.id = SBI_FWFT_LANDING_PAD,
+		.first_reg_num = offsetof(struct kvm_riscv_sbi_fwft, landing_pad.enable) /
+				 sizeof(unsigned long),
+		.supported = kvm_sbi_fwft_landing_pad_supported,
+		.reset = kvm_sbi_fwft_reset_landing_pad,
+		.set = kvm_sbi_fwft_set_landing_pad,
+		.get = kvm_sbi_fwft_get_landing_pad,
+	},
+	{
+		.id = SBI_FWFT_SHADOW_STACK,
+		.first_reg_num = offsetof(struct kvm_riscv_sbi_fwft, shadow_stack.enable) /
+				 sizeof(unsigned long),
+		.supported = kvm_sbi_fwft_shadow_stack_supported,
+		.reset = kvm_sbi_fwft_reset_shadow_stack,
+		.set = kvm_sbi_fwft_set_shadow_stack,
+		.get = kvm_sbi_fwft_get_shadow_stack,
+	},
 	{
 		.id = SBI_FWFT_PTE_AD_HW_UPDATING,
 		.first_reg_num = offsetof(struct kvm_riscv_sbi_fwft, pte_ad_hw_updating.enable) /
-- 
2.54.0