RISCV: KVM: Introduce vcpu->reset_cntx_lock

Originally, the use of kvm->lock in SBI_EXT_HSM_HART_START also avoids
the simultaneous updates to the reset context of target VCPU. Since this
lock has been replace with vcpu->mp_state_lock, and this new lock also
protects the vcpu->mp_state. We have to add a separate lock for
vcpu->reset_cntx.
Signed-off-by: Yong-Xuan Wang <yongxuan.wang@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20240417074528.16506-3-yongxuan.wang@sifive.comSigned-off-by: Anup Patel <anup@brainfault.org>

arch/riscv/include/asm/kvm_host.h

@@ -223,6 +223,7 @@ struct kvm_vcpu_arch {
 
 	/* CPU context upon Guest VCPU reset */
 	struct kvm_cpu_context guest_reset_context;
+	spinlock_t reset_cntx_lock;
 
 	/* CPU CSR context upon Guest VCPU reset */
 	struct kvm_vcpu_csr guest_reset_csr;

arch/riscv/kvm/vcpu.c

@@ -64,7 +64,9 @@ static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)
 
 	memcpy(csr, reset_csr, sizeof(*csr));
 
+	spin_lock(&vcpu->arch.reset_cntx_lock);
 	memcpy(cntx, reset_cntx, sizeof(*cntx));
+	spin_unlock(&vcpu->arch.reset_cntx_lock);
 
 	kvm_riscv_vcpu_fp_reset(vcpu);
 
@@ -121,12 +123,16 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
 	spin_lock_init(&vcpu->arch.hfence_lock);
 
 	/* Setup reset state of shadow SSTATUS and HSTATUS CSRs */
+	spin_lock_init(&vcpu->arch.reset_cntx_lock);
+
+	spin_lock(&vcpu->arch.reset_cntx_lock);
 	cntx = &vcpu->arch.guest_reset_context;
 	cntx->sstatus = SR_SPP | SR_SPIE;
 	cntx->hstatus = 0;
 	cntx->hstatus |= HSTATUS_VTW;
 	cntx->hstatus |= HSTATUS_SPVP;
 	cntx->hstatus |= HSTATUS_SPV;
+	spin_unlock(&vcpu->arch.reset_cntx_lock);
 
 	if (kvm_riscv_vcpu_alloc_vector_context(vcpu, cntx))
 		return -ENOMEM;

arch/riscv/kvm/vcpu_sbi_hsm.c

@@ -31,6 +31,7 @@ static int kvm_sbi_hsm_vcpu_start(struct kvm_vcpu *vcpu)
 		goto out;
 	}
 
+	spin_lock(&target_vcpu->arch.reset_cntx_lock);
 	reset_cntx = &target_vcpu->arch.guest_reset_context;
 	/* start address */
 	reset_cntx->sepc = cp->a1;
@@ -38,6 +39,8 @@ static int kvm_sbi_hsm_vcpu_start(struct kvm_vcpu *vcpu)
 	reset_cntx->a0 = target_vcpuid;
 	/* private data passed from kernel */
 	reset_cntx->a1 = cp->a2;
+	spin_unlock(&target_vcpu->arch.reset_cntx_lock);
+
 	kvm_make_request(KVM_REQ_VCPU_RESET, target_vcpu);
 
 	__kvm_riscv_vcpu_power_on(target_vcpu);