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[Backport] KVM: add 'vlenb' Vector CSR #264

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Merged
sterling-teng merged 3 commits into from
May 12, 2026
Merged

[Backport] KVM: add 'vlenb' Vector CSR #264

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8485afb
RISC-V: KVM: set 'vlenb' in kvm_riscv_vcpu_alloc_vector_context()
danielhb Dec 5, 2023
7594581
RISC-V: KVM: add 'vlenb' Vector CSR
danielhb Dec 5, 2023
cb2a9c3
RISC-V: KVM: fix stack overrun when loading vlenb
radimkrcmar Aug 5, 2025
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18 changes: 18 additions & 0 deletions arch/riscv/kvm/vcpu_vector.c
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Original file line number Diff line number Diff line change
Expand Up @@ -76,6 +76,7 @@ int kvm_riscv_vcpu_alloc_vector_context(struct kvm_vcpu *vcpu,
cntx->vector.datap = kmalloc(riscv_v_vsize, GFP_KERNEL);
if (!cntx->vector.datap)
return -ENOMEM;
cntx->vector.vlenb = riscv_v_vsize / 32;

vcpu->arch.host_context.vector.datap = kzalloc(riscv_v_vsize, GFP_KERNEL);
if (!vcpu->arch.host_context.vector.datap)
Expand Down Expand Up @@ -115,6 +116,9 @@ static int kvm_riscv_vcpu_vreg_addr(struct kvm_vcpu *vcpu,
case KVM_REG_RISCV_VECTOR_CSR_REG(vcsr):
*reg_addr = &cntx->vector.vcsr;
break;
case KVM_REG_RISCV_VECTOR_CSR_REG(vlenb):
*reg_addr = &cntx->vector.vlenb;
break;
case KVM_REG_RISCV_VECTOR_CSR_REG(datap):
default:
return -ENOENT;
Expand Down Expand Up @@ -173,6 +177,20 @@ int kvm_riscv_vcpu_set_reg_vector(struct kvm_vcpu *vcpu,
if (!riscv_isa_extension_available(isa, v))
return -ENOENT;

if (reg_num == KVM_REG_RISCV_VECTOR_CSR_REG(vlenb)) {
struct kvm_cpu_context *cntx = &vcpu->arch.guest_context;
unsigned long reg_val;

if (reg_size != sizeof(reg_val))
return -EINVAL;
if (copy_from_user(&reg_val, uaddr, reg_size))
return -EFAULT;
if (reg_val != cntx->vector.vlenb)
return -EINVAL;

return 0;
}

rc = kvm_riscv_vcpu_vreg_addr(vcpu, reg_num, reg_size, &reg_addr);
if (rc)
return rc;
Expand Down
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