RISC-V: KVM: Implement ONE_REG interface for SBI FWFT state

The KVM user-space needs a way to save/restore the state of
SBI FWFT features so implement SBI extension ONE_REG callbacks.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20250823155947.1354229-6-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>

Author: avpatel

arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h

@@ -16,6 +16,7 @@ struct kvm_sbi_fwft_feature;
 struct kvm_sbi_fwft_config {
 	const struct kvm_sbi_fwft_feature *feature;
 	bool supported;
+	bool enabled;
 	unsigned long flags;
 };
 

arch/riscv/include/uapi/asm/kvm.h

@@ -220,6 +220,18 @@ struct kvm_riscv_sbi_sta {
 	unsigned long shmem_hi;
 };
 
+struct kvm_riscv_sbi_fwft_feature {
+	unsigned long enable;
+	unsigned long flags;
+	unsigned long value;
+};
+
+/* SBI FWFT extension registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */
+struct kvm_riscv_sbi_fwft {
+	struct kvm_riscv_sbi_fwft_feature misaligned_deleg;
+	struct kvm_riscv_sbi_fwft_feature pointer_masking;
+};
+
 /* Possible states for kvm_riscv_timer */
 #define KVM_RISCV_TIMER_STATE_OFF	0
 #define KVM_RISCV_TIMER_STATE_ON	1
@@ -303,6 +315,9 @@ struct kvm_riscv_sbi_sta {
 #define KVM_REG_RISCV_SBI_STA		(0x0 << KVM_REG_RISCV_SUBTYPE_SHIFT)
 #define KVM_REG_RISCV_SBI_STA_REG(name)		\
 		(offsetof(struct kvm_riscv_sbi_sta, name) / sizeof(unsigned long))
+#define KVM_REG_RISCV_SBI_FWFT		(0x1 << KVM_REG_RISCV_SUBTYPE_SHIFT)
+#define KVM_REG_RISCV_SBI_FWFT_REG(name)	\
+		(offsetof(struct kvm_riscv_sbi_fwft, name) / sizeof(unsigned long))
 
 /* Device Control API: RISC-V AIA */
 #define KVM_DEV_RISCV_APLIC_ALIGN		0x1000

arch/riscv/kvm/vcpu_sbi_fwft.c

@@ -22,6 +22,11 @@ struct kvm_sbi_fwft_feature {
 	 */
 	enum sbi_fwft_feature_t id;
 
+	/**
+	 * @first_reg_num: ONE_REG index of the first ONE_REG register
+	 */
+	unsigned long first_reg_num;
+
 	/**
 	 * @supported: Check if the feature is supported on the vcpu
 	 *
@@ -44,7 +49,8 @@ struct kvm_sbi_fwft_feature {
 	 *
 	 * This callback is mandatory
 	 */
-	long (*set)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf, unsigned long value);
+	long (*set)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf,
+		    bool one_reg_access, unsigned long value);
 
 	/**
 	 * @get: Get the feature current value
@@ -53,7 +59,8 @@ struct kvm_sbi_fwft_feature {
 	 *
 	 * This callback is mandatory
 	 */
-	long (*get)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf, unsigned long *value);
+	long (*get)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf,
+		    bool one_reg_access, unsigned long *value);
 };
 
 static const enum sbi_fwft_feature_t kvm_fwft_defined_features[] = {
@@ -91,16 +98,18 @@ static void kvm_sbi_fwft_reset_misaligned_delegation(struct kvm_vcpu *vcpu)
 
 static long kvm_sbi_fwft_set_misaligned_delegation(struct kvm_vcpu *vcpu,
 					struct kvm_sbi_fwft_config *conf,
-					unsigned long value)
+					bool one_reg_access, unsigned long value)
 {
 	struct kvm_vcpu_config *cfg = &vcpu->arch.cfg;
 
 	if (value == 1) {
 		cfg->hedeleg |= MIS_DELEG;
-		csr_set(CSR_HEDELEG, MIS_DELEG);
+		if (!one_reg_access)
+			csr_set(CSR_HEDELEG, MIS_DELEG);
 	} else if (value == 0) {
 		cfg->hedeleg &= ~MIS_DELEG;
-		csr_clear(CSR_HEDELEG, MIS_DELEG);
+		if (!one_reg_access)
+			csr_clear(CSR_HEDELEG, MIS_DELEG);
 	} else {
 		return SBI_ERR_INVALID_PARAM;
 	}
@@ -110,10 +119,11 @@ static long kvm_sbi_fwft_set_misaligned_delegation(struct kvm_vcpu *vcpu,
 
 static long kvm_sbi_fwft_get_misaligned_delegation(struct kvm_vcpu *vcpu,
 					struct kvm_sbi_fwft_config *conf,
-					unsigned long *value)
+					bool one_reg_access, unsigned long *value)
 {
-	*value = (csr_read(CSR_HEDELEG) & MIS_DELEG) == MIS_DELEG;
+	struct kvm_vcpu_config *cfg = &vcpu->arch.cfg;
 
+	*value = (cfg->hedeleg & MIS_DELEG) == MIS_DELEG;
 	return SBI_SUCCESS;
 }
 
@@ -145,7 +155,7 @@ static void kvm_sbi_fwft_reset_pointer_masking_pmlen(struct kvm_vcpu *vcpu)
 
 static long kvm_sbi_fwft_set_pointer_masking_pmlen(struct kvm_vcpu *vcpu,
 						   struct kvm_sbi_fwft_config *conf,
-						   unsigned long value)
+						   bool one_reg_access, unsigned long value)
 {
 	struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
 	unsigned long pmm;
@@ -176,14 +186,15 @@ static long kvm_sbi_fwft_set_pointer_masking_pmlen(struct kvm_vcpu *vcpu,
 	 * update here so that VCPU see's pointer masking mode change
 	 * immediately.
 	 */
-	csr_write(CSR_HENVCFG, vcpu->arch.cfg.henvcfg);
+	if (!one_reg_access)
+		csr_write(CSR_HENVCFG, vcpu->arch.cfg.henvcfg);
 
 	return SBI_SUCCESS;
 }
 
 static long kvm_sbi_fwft_get_pointer_masking_pmlen(struct kvm_vcpu *vcpu,
 						   struct kvm_sbi_fwft_config *conf,
-						   unsigned long *value)
+						   bool one_reg_access, unsigned long *value)
 {
 	switch (vcpu->arch.cfg.henvcfg & ENVCFG_PMM) {
 	case ENVCFG_PMM_PMLEN_0:
@@ -207,6 +218,8 @@ static long kvm_sbi_fwft_get_pointer_masking_pmlen(struct kvm_vcpu *vcpu,
 static const struct kvm_sbi_fwft_feature features[] = {
 	{
 		.id = SBI_FWFT_MISALIGNED_EXC_DELEG,
+		.first_reg_num = offsetof(struct kvm_riscv_sbi_fwft, misaligned_deleg.enable) /
+				 sizeof(unsigned long),
 		.supported = kvm_sbi_fwft_misaligned_delegation_supported,
 		.reset = kvm_sbi_fwft_reset_misaligned_delegation,
 		.set = kvm_sbi_fwft_set_misaligned_delegation,
@@ -215,6 +228,8 @@ static const struct kvm_sbi_fwft_feature features[] = {
 #ifndef CONFIG_32BIT
 	{
 		.id = SBI_FWFT_POINTER_MASKING_PMLEN,
+		.first_reg_num = offsetof(struct kvm_riscv_sbi_fwft, pointer_masking.enable) /
+				 sizeof(unsigned long),
 		.supported = kvm_sbi_fwft_pointer_masking_pmlen_supported,
 		.reset = kvm_sbi_fwft_reset_pointer_masking_pmlen,
 		.set = kvm_sbi_fwft_set_pointer_masking_pmlen,
@@ -223,6 +238,20 @@ static const struct kvm_sbi_fwft_feature features[] = {
 #endif
 };
 
+static const struct kvm_sbi_fwft_feature *kvm_sbi_fwft_regnum_to_feature(unsigned long reg_num)
+{
+	const struct kvm_sbi_fwft_feature *feature;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(features); i++) {
+		feature = &features[i];
+		if (feature->first_reg_num <= reg_num && reg_num < (feature->first_reg_num + 3))
+			return feature;
+	}
+
+	return NULL;
+}
+
 static struct kvm_sbi_fwft_config *
 kvm_sbi_fwft_get_config(struct kvm_vcpu *vcpu, enum sbi_fwft_feature_t feature)
 {
@@ -250,7 +279,7 @@ static int kvm_fwft_get_feature(struct kvm_vcpu *vcpu, u32 feature,
 		return SBI_ERR_DENIED;
 	}
 
-	if (!tconf->supported)
+	if (!tconf->supported || !tconf->enabled)
 		return SBI_ERR_NOT_SUPPORTED;
 
 	*conf = tconf;
@@ -276,7 +305,7 @@ static int kvm_sbi_fwft_set(struct kvm_vcpu *vcpu, u32 feature,
 
 	conf->flags = flags;
 
-	return conf->feature->set(vcpu, conf, value);
+	return conf->feature->set(vcpu, conf, false, value);
 }
 
 static int kvm_sbi_fwft_get(struct kvm_vcpu *vcpu, unsigned long feature,
@@ -289,7 +318,7 @@ static int kvm_sbi_fwft_get(struct kvm_vcpu *vcpu, unsigned long feature,
 	if (ret)
 		return ret;
 
-	return conf->feature->get(vcpu, conf, value);
+	return conf->feature->get(vcpu, conf, false, value);
 }
 
 static int kvm_sbi_ext_fwft_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
@@ -336,6 +365,7 @@ static int kvm_sbi_ext_fwft_init(struct kvm_vcpu *vcpu)
 		else
 			conf->supported = true;
 
+		conf->enabled = conf->supported;
 		conf->feature = feature;
 	}
 
@@ -363,11 +393,152 @@ static void kvm_sbi_ext_fwft_reset(struct kvm_vcpu *vcpu)
 	}
 }
 
+static unsigned long kvm_sbi_ext_fwft_get_reg_count(struct kvm_vcpu *vcpu)
+{
+	unsigned long max_reg_count = sizeof(struct kvm_riscv_sbi_fwft) / sizeof(unsigned long);
+	const struct kvm_sbi_fwft_feature *feature;
+	struct kvm_sbi_fwft_config *conf;
+	unsigned long reg, ret = 0;
+
+	for (reg = 0; reg < max_reg_count; reg++) {
+		feature = kvm_sbi_fwft_regnum_to_feature(reg);
+		if (!feature)
+			continue;
+
+		conf = kvm_sbi_fwft_get_config(vcpu, feature->id);
+		if (!conf || !conf->supported)
+			continue;
+
+		ret++;
+	}
+
+	return ret;
+}
+
+static int kvm_sbi_ext_fwft_get_reg_id(struct kvm_vcpu *vcpu, int index, u64 *reg_id)
+{
+	int reg, max_reg_count = sizeof(struct kvm_riscv_sbi_fwft) / sizeof(unsigned long);
+	const struct kvm_sbi_fwft_feature *feature;
+	struct kvm_sbi_fwft_config *conf;
+	int idx = 0;
+
+	for (reg = 0; reg < max_reg_count; reg++) {
+		feature = kvm_sbi_fwft_regnum_to_feature(reg);
+		if (!feature)
+			continue;
+
+		conf = kvm_sbi_fwft_get_config(vcpu, feature->id);
+		if (!conf || !conf->supported)
+			continue;
+
+		if (index == idx) {
+			*reg_id = KVM_REG_RISCV |
+				  (IS_ENABLED(CONFIG_32BIT) ?
+				   KVM_REG_SIZE_U32 : KVM_REG_SIZE_U64) |
+				  KVM_REG_RISCV_SBI_STATE |
+				  KVM_REG_RISCV_SBI_FWFT | reg;
+			return 0;
+		}
+
+		idx++;
+	}
+
+	return -ENOENT;
+}
+
+static int kvm_sbi_ext_fwft_get_reg(struct kvm_vcpu *vcpu, unsigned long reg_num,
+				    unsigned long reg_size, void *reg_val)
+{
+	const struct kvm_sbi_fwft_feature *feature;
+	struct kvm_sbi_fwft_config *conf;
+	unsigned long *value;
+	int ret = 0;
+
+	if (reg_size != sizeof(unsigned long))
+		return -EINVAL;
+	value = reg_val;
+
+	feature = kvm_sbi_fwft_regnum_to_feature(reg_num);
+	if (!feature)
+		return -ENOENT;
+
+	conf = kvm_sbi_fwft_get_config(vcpu, feature->id);
+	if (!conf || !conf->supported)
+		return -ENOENT;
+
+	switch (reg_num - feature->first_reg_num) {
+	case 0:
+		*value = conf->enabled;
+		break;
+	case 1:
+		*value = conf->flags;
+		break;
+	case 2:
+		ret = conf->feature->get(vcpu, conf, true, value);
+		break;
+	default:
+		return -ENOENT;
+	}
+
+	return sbi_err_map_linux_errno(ret);
+}
+
+static int kvm_sbi_ext_fwft_set_reg(struct kvm_vcpu *vcpu, unsigned long reg_num,
+				    unsigned long reg_size, const void *reg_val)
+{
+	const struct kvm_sbi_fwft_feature *feature;
+	struct kvm_sbi_fwft_config *conf;
+	unsigned long value;
+	int ret = 0;
+
+	if (reg_size != sizeof(unsigned long))
+		return -EINVAL;
+	value = *(const unsigned long *)reg_val;
+
+	feature = kvm_sbi_fwft_regnum_to_feature(reg_num);
+	if (!feature)
+		return -ENOENT;
+
+	conf = kvm_sbi_fwft_get_config(vcpu, feature->id);
+	if (!conf || !conf->supported)
+		return -ENOENT;
+
+	switch (reg_num - feature->first_reg_num) {
+	case 0:
+		switch (value) {
+		case 0:
+			conf->enabled = false;
+			break;
+		case 1:
+			conf->enabled = true;
+			break;
+		default:
+			return -EINVAL;
+		}
+		break;
+	case 1:
+		conf->flags = value & SBI_FWFT_SET_FLAG_LOCK;
+		break;
+	case 2:
+		ret = conf->feature->set(vcpu, conf, true, value);
+		break;
+	default:
+		return -ENOENT;
+	}
+
+	return sbi_err_map_linux_errno(ret);
+}
+
 const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_fwft = {
 	.extid_start = SBI_EXT_FWFT,
 	.extid_end = SBI_EXT_FWFT,
 	.handler = kvm_sbi_ext_fwft_handler,
 	.init = kvm_sbi_ext_fwft_init,
 	.deinit = kvm_sbi_ext_fwft_deinit,
 	.reset = kvm_sbi_ext_fwft_reset,
+	.state_reg_subtype = KVM_REG_RISCV_SBI_FWFT,
+	.get_state_reg_count = kvm_sbi_ext_fwft_get_reg_count,
+	.get_state_reg_id = kvm_sbi_ext_fwft_get_reg_id,
+	.get_state_reg = kvm_sbi_ext_fwft_get_reg,
+	.set_state_reg = kvm_sbi_ext_fwft_set_reg,
 };