Re: [PATCH v3 17/17] RISC-V: KVM: add support for SBI_FWFT_MISALIGNED_DELEG

Andrew Jones
2025-03-13T15:23:16Z

On Mon, Mar 10, 2025 at 04:12:24PM +0100, Clément Léger wrote:
> SBI_FWFT_MISALIGNED_DELEG needs hedeleg to be modified to delegate
> misaligned load/store exceptions. Save and restore it during CPU
> load/put.
>
> Signed-off-by: Clément Léger <cleger@rivosinc.com>
> Reviewed-by: Deepak Gupta <debug@rivosinc.com>
> ---
> arch/riscv/kvm/vcpu.c | 3 +++
> arch/riscv/kvm/vcpu_sbi_fwft.c | 39 ++++++++++++++++++++++++++++++++++
> 2 files changed, 42 insertions(+)
>
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index 542747e2c7f5..d98e379945c3 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -646,6 +646,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
> {
> void *nsh;
> struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
> + struct kvm_vcpu_config *cfg = &vcpu->arch.cfg;
>
> vcpu->cpu = -1;
>
> @@ -671,6 +672,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
> csr->vstval = nacl_csr_read(nsh, CSR_VSTVAL);
> csr->hvip = nacl_csr_read(nsh, CSR_HVIP);
> csr->vsatp = nacl_csr_read(nsh, CSR_VSATP);
> + cfg->hedeleg = nacl_csr_read(nsh, CSR_HEDELEG);
> } else {
> csr->vsstatus = csr_read(CSR_VSSTATUS);
> csr->vsie = csr_read(CSR_VSIE);
> @@ -681,6 +683,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
> csr->vstval = csr_read(CSR_VSTVAL);
> csr->hvip = csr_read(CSR_HVIP);
> csr->vsatp = csr_read(CSR_VSATP);
> + cfg->hedeleg = csr_read(CSR_HEDELEG);
> }
> }
>
> diff --git a/arch/riscv/kvm/vcpu_sbi_fwft.c b/arch/riscv/kvm/vcpu_sbi_fwft.c
> index cce1e41d5490..756fda1cf2e7 100644
> --- a/arch/riscv/kvm/vcpu_sbi_fwft.c
> +++ b/arch/riscv/kvm/vcpu_sbi_fwft.c
> @@ -14,6 +14,8 @@
> #include <asm/kvm_vcpu_sbi.h>
> #include <asm/kvm_vcpu_sbi_fwft.h>
>
> +#define MIS_DELEG (BIT_ULL(EXC_LOAD_MISALIGNED) | BIT_ULL(EXC_STORE_MISALIGNED))
> +
> struct kvm_sbi_fwft_feature {
> /**
> * @id: Feature ID
> @@ -64,7 +66,44 @@ static bool kvm_fwft_is_defined_feature(enum sbi_fwft_feature_t feature)
> return false;
> }
>
> +static bool kvm_sbi_fwft_misaligned_delegation_supported(struct kvm_vcpu *vcpu)
> +{
> + if (!misaligned_traps_can_delegate())
> + return false;
> +
> + return true;

Just

return misaligned_traps_can_delegate();

> +}
> +
> +static int kvm_sbi_fwft_set_misaligned_delegation(struct kvm_vcpu *vcpu,
> + struct kvm_sbi_fwft_config *conf,
> + unsigned long value)
> +{
> + if (value == 1)
> + csr_set(CSR_HEDELEG, MIS_DELEG);
> + else if (value == 0)
> + csr_clear(CSR_HEDELEG, MIS_DELEG);
> + else
> + return SBI_ERR_INVALID_PARAM;
> +
> + return SBI_SUCCESS;
> +}
> +
> +static int kvm_sbi_fwft_get_misaligned_delegation(struct kvm_vcpu *vcpu,
> + struct kvm_sbi_fwft_config *conf,
> + unsigned long *value)
> +{
> + *value = (csr_read(CSR_HEDELEG) & MIS_DELEG) != 0;
> +
> + return SBI_SUCCESS;
> +}
> +
> static const struct kvm_sbi_fwft_feature features[] = {
> + {
> + .id = SBI_FWFT_MISALIGNED_EXC_DELEG,
> + .supported = kvm_sbi_fwft_misaligned_delegation_supported,
> + .set = kvm_sbi_fwft_set_misaligned_delegation,
> + .get = kvm_sbi_fwft_get_misaligned_delegation,
> + },
> };
>
> static struct kvm_sbi_fwft_config *
> --
> 2.47.2
>

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>