[PATCH v4 1/8] RISC-V: KVM: Add support for Svadu FWFT features

[Inochi Amaoto <inochiama@gmail.com>]

Hardware updating of PTE A/D bits is controlled through ADUE bit in
henvcfg Expose the feature only if both Svadu and Svade are supported
for VS-mode.

Allow the VMM to enable/disable this feature by change the ISA
extension state in the guest.

Assisted-by: YuanSheng:claude-4.7-opus
Co-developed-by: Quan Zhou <zhouquan@iscas.ac.cn>
Signed-off-by: Quan Zhou <zhouquan@iscas.ac.cn>
Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
---
 arch/riscv/include/uapi/asm/kvm.h |  1 +
 arch/riscv/kvm/vcpu_sbi_fwft.c    | 75 +++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+)

diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
index 504e73305343..7bbea8812d92 100644
--- a/arch/riscv/include/uapi/asm/kvm.h
+++ b/arch/riscv/include/uapi/asm/kvm.h
@@ -240,6 +240,7 @@ struct kvm_riscv_sbi_fwft_feature {
 struct kvm_riscv_sbi_fwft {
 	struct kvm_riscv_sbi_fwft_feature misaligned_deleg;
 	struct kvm_riscv_sbi_fwft_feature pointer_masking;
+	struct kvm_riscv_sbi_fwft_feature pte_ad_hw_updating;
 };
 
 /* If you need to interpret the index values, here is the key: */
diff --git a/arch/riscv/kvm/vcpu_sbi_fwft.c b/arch/riscv/kvm/vcpu_sbi_fwft.c
index ab39ac464ffd..7192c229a19e 100644
--- a/arch/riscv/kvm/vcpu_sbi_fwft.c
+++ b/arch/riscv/kvm/vcpu_sbi_fwft.c
@@ -94,6 +94,45 @@ static bool kvm_fwft_is_defined_feature(enum sbi_fwft_feature_t feature)
 	return false;
 }
 
+static void kvm_sbi_fwft_env_flag_reset_helper(struct kvm_vcpu *vcpu,
+					       u64 flag)
+{
+	vcpu->arch.cfg.henvcfg &= ~flag;
+}
+
+static long kvm_sbi_fwft_env_flag_set_helper(struct kvm_vcpu *vcpu,
+					     struct kvm_sbi_fwft_config *conf,
+					     bool one_reg_access,
+					     unsigned long value, u64 flag)
+{
+	struct kvm_vcpu_config *cfg = &vcpu->arch.cfg;
+
+	if (value == 0)
+		cfg->henvcfg &= ~flag;
+	else if (value == 1)
+		cfg->henvcfg |= flag;
+	else
+		return SBI_ERR_INVALID_PARAM;
+
+	if (!one_reg_access) {
+		csr_write(CSR_HENVCFG, vcpu->arch.cfg.henvcfg);
+		if (IS_ENABLED(CONFIG_32BIT))
+			csr_write(CSR_HENVCFGH, vcpu->arch.cfg.henvcfg >> 32);
+	}
+
+	return SBI_SUCCESS;
+}
+
+static long kvm_sbi_fwft_env_flag_get_helper(struct kvm_vcpu *vcpu,
+					     struct kvm_sbi_fwft_config *conf,
+					     bool one_reg_access,
+					     unsigned long *value, u64 flag)
+{
+	*value = (vcpu->arch.cfg.henvcfg & flag) == flag;
+
+	return SBI_SUCCESS;
+}
+
 static bool kvm_sbi_fwft_misaligned_delegation_supported(struct kvm_vcpu *vcpu)
 {
 	return misaligned_traps_can_delegate();
@@ -137,6 +176,33 @@ static long kvm_sbi_fwft_get_misaligned_delegation(struct kvm_vcpu *vcpu,
 	return SBI_SUCCESS;
 }
 
+static bool kvm_sbi_fwft_pte_ad_hw_updating_supported(struct kvm_vcpu *vcpu)
+{
+	return riscv_isa_extension_available(vcpu->arch.isa, SVADU) &&
+		riscv_isa_extension_available(vcpu->arch.isa, SVADE);
+}
+
+static void kvm_sbi_fwft_reset_pte_ad_hw_updating(struct kvm_vcpu *vcpu)
+{
+	kvm_sbi_fwft_env_flag_reset_helper(vcpu, ENVCFG_ADUE);
+}
+
+static long kvm_sbi_fwft_set_pte_ad_hw_updating(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_ADUE);
+}
+
+static long kvm_sbi_fwft_get_pte_ad_hw_updating(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_ADUE);
+}
+
 #ifndef CONFIG_32BIT
 
 static bool try_to_set_pmm(unsigned long value)
@@ -246,6 +312,15 @@ 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_PTE_AD_HW_UPDATING,
+		.first_reg_num = offsetof(struct kvm_riscv_sbi_fwft, pte_ad_hw_updating.enable) /
+				 sizeof(unsigned long),
+		.supported = kvm_sbi_fwft_pte_ad_hw_updating_supported,
+		.reset = kvm_sbi_fwft_reset_pte_ad_hw_updating,
+		.set = kvm_sbi_fwft_set_pte_ad_hw_updating,
+		.get = kvm_sbi_fwft_get_pte_ad_hw_updating,
+	},
 #ifndef CONFIG_32BIT
 	{
 		.id = SBI_FWFT_POINTER_MASKING_PMLEN,
-- 
2.55.0