linux-kernel - [PATCH v2 4/5] RISC-V: KVM: Enable envcfg and sstateen bits lazily

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Message-Id: <20250522-kvm_lazy_enable_stateen-v2-4-b7a84991f1c4@rivosinc.com>
Date: Thu, 22 May 2025 13:35:28 -0700
From: Atish Patra <atishp@...osinc.com>
To: Anup Patel <anup@...infault.org>, Atish Patra <atishp@...shpatra.org>, 
 Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Alexandre Ghiti <alex@...ti.fr>
Cc: kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org, 
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 Atish Patra <atishp@...osinc.com>
Subject: [PATCH v2 4/5] RISC-V: KVM: Enable envcfg and sstateen bits lazily

SENVCFG and SSTATEEN CSRs are controlled by HSENVCFG(62) and
SSTATEEN0(63) bits in hstateen. Enable them lazily at runtime
instead of bootime.

Signed-off-by: Atish Patra <atishp@...osinc.com>
---
 arch/riscv/kvm/vcpu_insn.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/arch/riscv/kvm/vcpu_insn.c b/arch/riscv/kvm/vcpu_insn.c
index ef4fcb641f1c..6f2bba7533cf 100644
--- a/arch/riscv/kvm/vcpu_insn.c
+++ b/arch/riscv/kvm/vcpu_insn.c
@@ -265,9 +265,37 @@ int kvm_riscv_vcpu_hstateen_lazy_enable(struct kvm_vcpu *vcpu, unsigned int csr_
 	return KVM_INSN_CONTINUE_SAME_SEPC;
 }
 
+static int kvm_riscv_vcpu_hstateen_enable_senvcfg(struct kvm_vcpu *vcpu,
+						  unsigned int csr_num,
+						  unsigned long *val,
+						  unsigned long new_val,
+						  unsigned long wr_mask)
+{
+	return kvm_riscv_vcpu_hstateen_lazy_enable(vcpu, csr_num, SMSTATEEN0_HSENVCFG);
+}
+
+static int kvm_riscv_vcpu_hstateen_enable_stateen(struct kvm_vcpu *vcpu,
+						  unsigned int csr_num,
+						  unsigned long *val,
+						  unsigned long new_val,
+						  unsigned long wr_mask)
+{
+	const unsigned long *isa = vcpu->arch.isa;
+
+	if (riscv_isa_extension_available(isa, SMSTATEEN))
+		return kvm_riscv_vcpu_hstateen_lazy_enable(vcpu, csr_num, SMSTATEEN0_SSTATEEN0);
+	else
+		return KVM_INSN_EXIT_TO_USER_SPACE;
+}
+
+#define KVM_RISCV_VCPU_STATEEN_CSR_FUNCS \
+{ .base = CSR_SENVCFG,    .count = 1, .func = kvm_riscv_vcpu_hstateen_enable_senvcfg }, \
+{ .base = CSR_SSTATEEN0,  .count = 1, .func = kvm_riscv_vcpu_hstateen_enable_stateen },\
+
 static const struct csr_func csr_funcs[] = {
 	KVM_RISCV_VCPU_AIA_CSR_FUNCS
 	KVM_RISCV_VCPU_HPMCOUNTER_CSR_FUNCS
+	KVM_RISCV_VCPU_STATEEN_CSR_FUNCS
 	{ .base = CSR_SEED, .count = 1, .func = seed_csr_rmw },
 #ifdef CONFIG_32BIT
 	KVM_RISCV_VCPU_AIA_CSR_32BIT_FUNCS

-- 
2.43.0