Re: [PATCH v3 5/8] RISC-V: KVM: Implement subtype for CSR ONE_REG interface

Atish Patra
2023-04-04T00:54:43Z

On Mon, Apr 3, 2023 at 3:03 PM Anup Patel <apatel@ventanamicro.com> wrote:
>
> To make the CSR ONE_REG interface extensible, we implement subtype
> for the CSR ONE_REG IDs. The existing CSR ONE_REG IDs are treated
> as subtype = 0 (aka General CSRs).
>
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> ---
> arch/riscv/include/uapi/asm/kvm.h | 3 +-
> arch/riscv/kvm/vcpu.c | 88 +++++++++++++++++++++++--------
> 2 files changed, 69 insertions(+), 22 deletions(-)
>
> diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
> index 47a7c3958229..182023dc9a51 100644
> --- a/arch/riscv/include/uapi/asm/kvm.h
> +++ b/arch/riscv/include/uapi/asm/kvm.h
> @@ -65,7 +65,7 @@ struct kvm_riscv_core {
> #define KVM_RISCV_MODE_S 1
> #define KVM_RISCV_MODE_U 0
>
> -/* CSR registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */
> +/* General CSR registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */
> struct kvm_riscv_csr {
> unsigned long sstatus;
> unsigned long sie;
> @@ -152,6 +152,7 @@ enum KVM_RISCV_SBI_EXT_ID {
>
> /* Control and status registers are mapped as type 3 */
> #define KVM_REG_RISCV_CSR (0x03 << KVM_REG_RISCV_TYPE_SHIFT)
> +#define KVM_REG_RISCV_CSR_GENERAL (0x0 << KVM_REG_RISCV_SUBTYPE_SHIFT)
> #define KVM_REG_RISCV_CSR_REG(name) \
> (offsetof(struct kvm_riscv_csr, name) / sizeof(unsigned long))
>
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index 1fd54ec15622..aca6b4fb7519 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -460,27 +460,72 @@ static int kvm_riscv_vcpu_set_reg_core(struct kvm_vcpu *vcpu,
> return 0;
> }
>
> +static int kvm_riscv_vcpu_general_get_csr(struct kvm_vcpu *vcpu,
> + unsigned long reg_num,
> + unsigned long *out_val)
> +{
> + struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
> +
> + if (reg_num >= sizeof(struct kvm_riscv_csr) / sizeof(unsigned long))
> + return -EINVAL;
> +
> + if (reg_num == KVM_REG_RISCV_CSR_REG(sip)) {
> + kvm_riscv_vcpu_flush_interrupts(vcpu);
> + *out_val = (csr->hvip >> VSIP_TO_HVIP_SHIFT) & VSIP_VALID_MASK;
> + } else
> + *out_val = ((unsigned long *)csr)[reg_num];
> +
> + return 0;
> +}
> +
> +static inline int kvm_riscv_vcpu_general_set_csr(struct kvm_vcpu *vcpu,
> + unsigned long reg_num,
> + unsigned long reg_val)
> +{
> + struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
> +
> + if (reg_num >= sizeof(struct kvm_riscv_csr) / sizeof(unsigned long))
> + return -EINVAL;
> +
> + if (reg_num == KVM_REG_RISCV_CSR_REG(sip)) {
> + reg_val &= VSIP_VALID_MASK;
> + reg_val <<= VSIP_TO_HVIP_SHIFT;
> + }
> +
> + ((unsigned long *)csr)[reg_num] = reg_val;
> +
> + if (reg_num == KVM_REG_RISCV_CSR_REG(sip))
> + WRITE_ONCE(vcpu->arch.irqs_pending_mask, 0);
> +
> + return 0;
> +}
> +
> static int kvm_riscv_vcpu_get_reg_csr(struct kvm_vcpu *vcpu,
> const struct kvm_one_reg *reg)
> {
> - struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
> + int rc;
> unsigned long __user *uaddr =
> (unsigned long __user *)(unsigned long)reg->addr;
> unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK |
> KVM_REG_SIZE_MASK |
> KVM_REG_RISCV_CSR);
> - unsigned long reg_val;
> + unsigned long reg_val, reg_subtype;
>
> if (KVM_REG_SIZE(reg->id) != sizeof(unsigned long))
> return -EINVAL;
> - if (reg_num >= sizeof(struct kvm_riscv_csr) / sizeof(unsigned long))
> - return -EINVAL;
>
> - if (reg_num == KVM_REG_RISCV_CSR_REG(sip)) {
> - kvm_riscv_vcpu_flush_interrupts(vcpu);
> - reg_val = (csr->hvip >> VSIP_TO_HVIP_SHIFT) & VSIP_VALID_MASK;
> - } else
> - reg_val = ((unsigned long *)csr)[reg_num];
> + reg_subtype = reg_num & KVM_REG_RISCV_SUBTYPE_MASK;
> + reg_num &= ~KVM_REG_RISCV_SUBTYPE_MASK;
> + switch (reg_subtype) {
> + case KVM_REG_RISCV_CSR_GENERAL:
> + rc = kvm_riscv_vcpu_general_get_csr(vcpu, reg_num, &reg_val);
> + break;
> + default:
> + rc = -EINVAL;
> + break;
> + }
> + if (rc)
> + return rc;
>
> if (copy_to_user(uaddr, &reg_val, KVM_REG_SIZE(reg->id)))
> return -EFAULT;
> @@ -491,31 +536,32 @@ static int kvm_riscv_vcpu_get_reg_csr(struct kvm_vcpu *vcpu,
> static int kvm_riscv_vcpu_set_reg_csr(struct kvm_vcpu *vcpu,
> const struct kvm_one_reg *reg)
> {
> - struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
> + int rc;
> unsigned long __user *uaddr =
> (unsigned long __user *)(unsigned long)reg->addr;
> unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK |
> KVM_REG_SIZE_MASK |
> KVM_REG_RISCV_CSR);
> - unsigned long reg_val;
> + unsigned long reg_val, reg_subtype;
>
> if (KVM_REG_SIZE(reg->id) != sizeof(unsigned long))
> return -EINVAL;
> - if (reg_num >= sizeof(struct kvm_riscv_csr) / sizeof(unsigned long))
> - return -EINVAL;
>
> if (copy_from_user(&reg_val, uaddr, KVM_REG_SIZE(reg->id)))
> return -EFAULT;
>
> - if (reg_num == KVM_REG_RISCV_CSR_REG(sip)) {
> - reg_val &= VSIP_VALID_MASK;
> - reg_val <<= VSIP_TO_HVIP_SHIFT;
> + reg_subtype = reg_num & KVM_REG_RISCV_SUBTYPE_MASK;
> + reg_num &= ~KVM_REG_RISCV_SUBTYPE_MASK;
> + switch (reg_subtype) {
> + case KVM_REG_RISCV_CSR_GENERAL:
> + rc = kvm_riscv_vcpu_general_set_csr(vcpu, reg_num, reg_val);
> + break;
> + default:
> + rc = -EINVAL;
> + break;
> }
> -
> - ((unsigned long *)csr)[reg_num] = reg_val;
> -
> - if (reg_num == KVM_REG_RISCV_CSR_REG(sip))
> - WRITE_ONCE(vcpu->arch.irqs_pending_mask, 0);
> + if (rc)
> + return rc;
>
> return 0;
> }
> --
> 2.34.1
>

Reviewed-by: Atish Patra <atishp@rivosinc.com>

--
Regards,
Atish