Re: [PATCH v5 13/13] RISC-V: KVM: add support for SBI_FWFT_MISALIGNED_DELEG

Clément Léger
2025-04-24T13:49:26Z

On 24/04/2025 13:34, Andrew Jones wrote:
> On Thu, Apr 17, 2025 at 02:20:00PM +0200, 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>
>> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
>> ---
>> arch/riscv/kvm/vcpu.c | 3 +++
>> arch/riscv/kvm/vcpu_sbi_fwft.c | 36 ++++++++++++++++++++++++++++++++++
>> 2 files changed, 39 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 b0f66c7bf010..237edaefa267 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
>> @@ -68,7 +70,41 @@ 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)
>> +{
>> + return misaligned_traps_can_delegate();
>> +}
>> +
>> +static long 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 long 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;
>
> This should be
>
> (csr_read(CSR_HEDELEG) & MIS_DELEG) == MIS_DELEG;

Hum yeah indeed, I didn't thought that someone would ony delegate load
or stores.

I'll fix that,

Thanks,

Clément

>
>> +
>> + 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 *
>> --
>> 2.49.0
>>
>
> Thanks,
> drew