linux-kernel - Re: [PATCH v8 14/14] RISC-V: KVM: add support for SBI_FWFT_MISALIGNED

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Message-ID: <CAAhSdy1qnRYOh0ka4PeJDf5ybviMrf+bpYaOOka3BXVmwAPSoQ@mail.gmail.com>
Date: Thu, 12 Jun 2025 18:56:33 +0530
From: Anup Patel <anup@...infault.org>
To: Clément Léger <cleger@...osinc.com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Atish Patra <atishp@...shpatra.org>, Shuah Khan <shuah@...nel.org>, 
	Jonathan Corbet <corbet@....net>, linux-riscv@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, kvm@...r.kernel.org, 
	kvm-riscv@...ts.infradead.org, linux-kselftest@...r.kernel.org, 
	Samuel Holland <samuel.holland@...ive.com>, Andrew Jones <ajones@...tanamicro.com>, 
	Deepak Gupta <debug@...osinc.com>, Charlie Jenkins <charlie@...osinc.com>, 
	Atish Patra <atishp@...osinc.com>
Subject: Re: [PATCH v8 14/14] RISC-V: KVM: add support for SBI_FWFT_MISALIGNED_DELEG

On Fri, May 23, 2025 at 3:53 PM Clément Léger <cleger@...osinc.com> 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@...osinc.com>
> Reviewed-by: Deepak Gupta <debug@...osinc.com>
> Reviewed-by: Andrew Jones <ajones@...tanamicro.com>
> Reviewed-by: Atish Patra <atishp@...osinc.com>

Queued this patch for Linux-6.17

Thanks,
Anup

> ---
>  arch/riscv/kvm/vcpu_sbi_fwft.c | 41 ++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
>
> diff --git a/arch/riscv/kvm/vcpu_sbi_fwft.c b/arch/riscv/kvm/vcpu_sbi_fwft.c
> index b0f66c7bf010..6770c043bbcb 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 +70,46 @@ 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)
> +{
> +       struct kvm_vcpu_config *cfg = &vcpu->arch.cfg;
> +
> +       if (value == 1) {
> +               cfg->hedeleg |= MIS_DELEG;
> +               csr_set(CSR_HEDELEG, MIS_DELEG);
> +       } else if (value == 0) {
> +               cfg->hedeleg &= ~MIS_DELEG;
> +               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) == MIS_DELEG;
> +
> +       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
>