[PATCH v4 4/8] RISC-V: KVM: Add ssp context save/restore

[Inochi Amaoto <inochiama@gmail.com>]

Add ssp context save/restore for guest VCPUs and also add it to the
ONE_REG interface to allow its access from user space.

Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
---
 arch/riscv/include/asm/kvm_host.h |  7 ++++
 arch/riscv/include/uapi/asm/kvm.h |  8 ++++
 arch/riscv/kvm/vcpu.c             |  6 +++
 arch/riscv/kvm/vcpu_onereg.c      | 66 ++++++++++++++++++++++++++++++-
 4 files changed, 85 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index 60017ceec9d2..e5ed3b0e5a55 100644
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -163,6 +163,10 @@ struct kvm_vcpu_smstateen_csr {
 	unsigned long sstateen0;
 };
 
+struct kvm_vcpu_zicfiss_csr {
+	unsigned long ssp;
+};
+
 struct kvm_vcpu_reset_state {
 	spinlock_t lock;
 	unsigned long pc;
@@ -203,6 +207,9 @@ struct kvm_vcpu_arch {
 	/* CPU Smstateen CSR context of Guest VCPU */
 	struct kvm_vcpu_smstateen_csr smstateen_csr;
 
+	/* CPU Zicfiss CSR context of Guest VCPU */
+	struct kvm_vcpu_zicfiss_csr zicfiss_csr;
+
 	/* CPU reset state of Guest VCPU */
 	struct kvm_vcpu_reset_state reset_state;
 
diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
index a27de850fa4c..fd4c81697617 100644
--- a/arch/riscv/include/uapi/asm/kvm.h
+++ b/arch/riscv/include/uapi/asm/kvm.h
@@ -102,6 +102,11 @@ struct kvm_riscv_smstateen_csr {
 	unsigned long sstateen0;
 };
 
+/* Zicfiss CSR for KVM_GET_ONE_REG and KVM_SET_ONE_REG */
+struct kvm_riscv_zicfiss_csr {
+	unsigned long ssp;
+};
+
 /* TIMER registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */
 struct kvm_riscv_timer {
 	__u64 frequency;
@@ -266,12 +271,15 @@ struct kvm_riscv_sbi_fwft {
 #define KVM_REG_RISCV_CSR_GENERAL	(0x0 << KVM_REG_RISCV_SUBTYPE_SHIFT)
 #define KVM_REG_RISCV_CSR_AIA		(0x1 << KVM_REG_RISCV_SUBTYPE_SHIFT)
 #define KVM_REG_RISCV_CSR_SMSTATEEN	(0x2 << KVM_REG_RISCV_SUBTYPE_SHIFT)
+#define KVM_REG_RISCV_CSR_ZICFISS	(0x3 << KVM_REG_RISCV_SUBTYPE_SHIFT)
 #define KVM_REG_RISCV_CSR_REG(name)	\
 		(offsetof(struct kvm_riscv_csr, name) / sizeof(unsigned long))
 #define KVM_REG_RISCV_CSR_AIA_REG(name)	\
 	(offsetof(struct kvm_riscv_aia_csr, name) / sizeof(unsigned long))
 #define KVM_REG_RISCV_CSR_SMSTATEEN_REG(name)  \
 	(offsetof(struct kvm_riscv_smstateen_csr, name) / sizeof(unsigned long))
+#define KVM_REG_RISCV_CSR_ZICFISS_REG(name)  \
+	(offsetof(struct kvm_riscv_zicfiss_csr, name) / sizeof(unsigned long))
 
 /* Timer registers are mapped as type 4 */
 #define KVM_REG_RISCV_TIMER		(0x04 << KVM_REG_RISCV_TYPE_SHIFT)
diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index cf6e231e76e2..1c2775a4834e 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -720,6 +720,7 @@ static void kvm_riscv_update_hvip(struct kvm_vcpu *vcpu)
 
 static __always_inline void kvm_riscv_vcpu_swap_in_guest_state(struct kvm_vcpu *vcpu)
 {
+	struct kvm_vcpu_zicfiss_csr *zicficsr = &vcpu->arch.zicfiss_csr;
 	struct kvm_vcpu_smstateen_csr *smcsr = &vcpu->arch.smstateen_csr;
 	struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
 
@@ -727,10 +728,13 @@ static __always_inline void kvm_riscv_vcpu_swap_in_guest_state(struct kvm_vcpu *
 	vcpu->arch.host_senvcfg = csr_swap(CSR_SENVCFG, csr->senvcfg);
 	if (riscv_has_extension_unlikely(RISCV_ISA_EXT_SMSTATEEN))
 		vcpu->arch.host_sstateen0 = csr_swap(CSR_SSTATEEN0, smcsr->sstateen0);
+	if (riscv_has_extension_unlikely(RISCV_ISA_EXT_ZICFISS))
+		csr_write(CSR_SSP, zicficsr->ssp);
 }
 
 static __always_inline void kvm_riscv_vcpu_swap_in_host_state(struct kvm_vcpu *vcpu)
 {
+	struct kvm_vcpu_zicfiss_csr *zicficsr = &vcpu->arch.zicfiss_csr;
 	struct kvm_vcpu_smstateen_csr *smcsr = &vcpu->arch.smstateen_csr;
 	struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
 
@@ -738,6 +742,8 @@ static __always_inline void kvm_riscv_vcpu_swap_in_host_state(struct kvm_vcpu *v
 	csr->senvcfg = csr_swap(CSR_SENVCFG, vcpu->arch.host_senvcfg);
 	if (riscv_has_extension_unlikely(RISCV_ISA_EXT_SMSTATEEN))
 		smcsr->sstateen0 = csr_swap(CSR_SSTATEEN0, vcpu->arch.host_sstateen0);
+	if (riscv_has_extension_unlikely(RISCV_ISA_EXT_ZICFISS))
+		zicficsr->ssp = csr_swap(CSR_SSP, 0);
 }
 
 /*
diff --git a/arch/riscv/kvm/vcpu_onereg.c b/arch/riscv/kvm/vcpu_onereg.c
index bb920e8923c9..bd59aebc8b2e 100644
--- a/arch/riscv/kvm/vcpu_onereg.c
+++ b/arch/riscv/kvm/vcpu_onereg.c
@@ -355,6 +355,44 @@ static int kvm_riscv_vcpu_smstateen_get_csr(struct kvm_vcpu *vcpu,
 	return 0;
 }
 
+static inline int kvm_riscv_vcpu_zicfiss_set_csr(struct kvm_vcpu *vcpu,
+						 unsigned long reg_num,
+						 unsigned long reg_val)
+{
+	struct kvm_vcpu_zicfiss_csr *csr = &vcpu->arch.zicfiss_csr;
+	unsigned long regs_max = sizeof(struct kvm_vcpu_zicfiss_csr) /
+		sizeof(unsigned long);
+
+	if (!riscv_isa_extension_available(vcpu->arch.isa, ZICFISS))
+		return -ENOENT;
+	if (reg_num >= regs_max)
+		return -ENOENT;
+
+	reg_num = array_index_nospec(reg_num, regs_max);
+
+	((unsigned long *)csr)[reg_num] = reg_val;
+	return 0;
+}
+
+static int kvm_riscv_vcpu_zicfiss_get_csr(struct kvm_vcpu *vcpu,
+					  unsigned long reg_num,
+					  unsigned long *out_val)
+{
+	struct kvm_vcpu_zicfiss_csr *csr = &vcpu->arch.zicfiss_csr;
+	unsigned long regs_max = sizeof(struct kvm_vcpu_zicfiss_csr) /
+		sizeof(unsigned long);
+
+	if (!riscv_isa_extension_available(vcpu->arch.isa, ZICFISS))
+		return -ENOENT;
+	if (reg_num >= regs_max)
+		return -ENOENT;
+
+	reg_num = array_index_nospec(reg_num, regs_max);
+
+	*out_val = ((unsigned long *)csr)[reg_num];
+	return 0;
+}
+
 static int kvm_riscv_vcpu_get_reg_csr(struct kvm_vcpu *vcpu,
 				      const struct kvm_one_reg *reg)
 {
@@ -381,6 +419,9 @@ static int kvm_riscv_vcpu_get_reg_csr(struct kvm_vcpu *vcpu,
 	case KVM_REG_RISCV_CSR_SMSTATEEN:
 		rc = kvm_riscv_vcpu_smstateen_get_csr(vcpu, reg_num, &reg_val);
 		break;
+	case KVM_REG_RISCV_CSR_ZICFISS:
+		rc = kvm_riscv_vcpu_zicfiss_get_csr(vcpu, reg_num, &reg_val);
+		break;
 	default:
 		rc = -ENOENT;
 		break;
@@ -423,6 +464,9 @@ static int kvm_riscv_vcpu_set_reg_csr(struct kvm_vcpu *vcpu,
 	case KVM_REG_RISCV_CSR_SMSTATEEN:
 		rc = kvm_riscv_vcpu_smstateen_set_csr(vcpu, reg_num, reg_val);
 		break;
+	case KVM_REG_RISCV_CSR_ZICFISS:
+		rc = kvm_riscv_vcpu_zicfiss_set_csr(vcpu, reg_num, reg_val);
+		break;
 	default:
 		rc = -ENOENT;
 		break;
@@ -688,7 +732,7 @@ static int copy_csr_reg_indices(const struct kvm_vcpu *vcpu,
 				u64 __user *uindices)
 {
 	int n1 = sizeof(struct kvm_riscv_csr) / sizeof(unsigned long);
-	int n2 = 0, n3 = 0;
+	int n2 = 0, n3 = 0, n4 = 0;
 
 	/* copy general csr regs */
 	for (int i = 0; i < n1; i++) {
@@ -740,7 +784,25 @@ static int copy_csr_reg_indices(const struct kvm_vcpu *vcpu,
 		}
 	}
 
-	return n1 + n2 + n3;
+	/* copy Zicfiss csr regs */
+	if (riscv_isa_extension_available(vcpu->arch.isa, ZICFISS)) {
+		n4 = sizeof(struct kvm_riscv_zicfiss_csr) / sizeof(unsigned long);
+
+		for (int i = 0; i < n4; i++) {
+			u64 size = IS_ENABLED(CONFIG_32BIT) ?
+				   KVM_REG_SIZE_U32 : KVM_REG_SIZE_U64;
+			u64 reg = KVM_REG_RISCV | size | KVM_REG_RISCV_CSR |
+					  KVM_REG_RISCV_CSR_ZICFISS | i;
+
+			if (uindices) {
+				if (put_user(reg, uindices))
+					return -EFAULT;
+				uindices++;
+			}
+		}
+	}
+
+	return n1 + n2 + n3 + n4;
 }
 
 static inline unsigned long num_timer_regs(void)
-- 
2.55.0