linux-kernel - Re: [PATCH 2/6] RISC-V: KVM: Introduce feature specific reset for SBI FWFT

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Message-ID: <20250815-30ccdcf30a9746a3b2443b4b@orel>
Date: Fri, 15 Aug 2025 15:14:36 -0500
From: Andrew Jones <ajones@...tanamicro.com>
To: Anup Patel <apatel@...tanamicro.com>
Cc: Atish Patra <atish.patra@...ux.dev>, 
	Palmer Dabbelt <palmer@...belt.com>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Alexandre Ghiti <alex@...ti.fr>, Anup Patel <anup@...infault.org>, 
	Paolo Bonzini <pbonzini@...hat.com>, Shuah Khan <shuah@...nel.org>, kvm@...r.kernel.org, 
	kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 2/6] RISC-V: KVM: Introduce feature specific reset for
 SBI FWFT

On Thu, Aug 14, 2025 at 09:25:44PM +0530, Anup Patel wrote:
> The SBI FWFT feature values must be reset upon VCPU reset so
> introduce feature specific reset callback for this purpose.
> 
> Signed-off-by: Anup Patel <apatel@...tanamicro.com>
> ---
>  arch/riscv/kvm/vcpu_sbi_fwft.c | 30 ++++++++++++++++++++++++++++--
>  1 file changed, 28 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/riscv/kvm/vcpu_sbi_fwft.c b/arch/riscv/kvm/vcpu_sbi_fwft.c
> index 164a01288b0a..5a3bad0f9330 100644
> --- a/arch/riscv/kvm/vcpu_sbi_fwft.c
> +++ b/arch/riscv/kvm/vcpu_sbi_fwft.c
> @@ -30,6 +30,13 @@ struct kvm_sbi_fwft_feature {
>  	 */
>  	bool (*supported)(struct kvm_vcpu *vcpu);
>  
> +	/**
> +	 * @reset: Reset the feature value irrespective whether feature is supported or not
> +	 *
> +	 * This callback is mandatory
> +	 */
> +	void (*reset)(struct kvm_vcpu *vcpu);
> +
>  	/**
>  	 * @set: Set the feature value
>  	 *
> @@ -75,6 +82,13 @@ static bool kvm_sbi_fwft_misaligned_delegation_supported(struct kvm_vcpu *vcpu)
>  	return misaligned_traps_can_delegate();
>  }
>  
> +static void kvm_sbi_fwft_reset_misaligned_delegation(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_vcpu_config *cfg = &vcpu->arch.cfg;
> +
> +	cfg->hedeleg &= ~MIS_DELEG;
> +}
> +
>  static long kvm_sbi_fwft_set_misaligned_delegation(struct kvm_vcpu *vcpu,
>  					struct kvm_sbi_fwft_config *conf,
>  					unsigned long value)
> @@ -124,6 +138,11 @@ static bool kvm_sbi_fwft_pointer_masking_pmlen_supported(struct kvm_vcpu *vcpu)
>  	return fwft->have_vs_pmlen_7 || fwft->have_vs_pmlen_16;
>  }
>  
> +static void kvm_sbi_fwft_reset_pointer_masking_pmlen(struct kvm_vcpu *vcpu)
> +{
> +	vcpu->arch.cfg.henvcfg &= ~ENVCFG_PMM;
> +}
> +
>  static long kvm_sbi_fwft_set_pointer_masking_pmlen(struct kvm_vcpu *vcpu,
>  						   struct kvm_sbi_fwft_config *conf,
>  						   unsigned long value)
> @@ -180,6 +199,7 @@ static const struct kvm_sbi_fwft_feature features[] = {
>  	{
>  		.id = SBI_FWFT_MISALIGNED_EXC_DELEG,
>  		.supported = kvm_sbi_fwft_misaligned_delegation_supported,
> +		.reset = kvm_sbi_fwft_reset_misaligned_delegation,
>  		.set = kvm_sbi_fwft_set_misaligned_delegation,
>  		.get = kvm_sbi_fwft_get_misaligned_delegation,
>  	},
> @@ -187,6 +207,7 @@ static const struct kvm_sbi_fwft_feature features[] = {
>  	{
>  		.id = SBI_FWFT_POINTER_MASKING_PMLEN,
>  		.supported = kvm_sbi_fwft_pointer_masking_pmlen_supported,
> +		.reset = kvm_sbi_fwft_reset_pointer_masking_pmlen,
>  		.set = kvm_sbi_fwft_set_pointer_masking_pmlen,
>  		.get = kvm_sbi_fwft_get_pointer_masking_pmlen,
>  	},
> @@ -321,11 +342,16 @@ static void kvm_sbi_ext_fwft_deinit(struct kvm_vcpu *vcpu)
>  
>  static void kvm_sbi_ext_fwft_reset(struct kvm_vcpu *vcpu)
>  {
> -	int i;
>  	struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
> +	const struct kvm_sbi_fwft_feature *feature;
> +	int i;
>  
> -	for (i = 0; i < ARRAY_SIZE(features); i++)
> +	for (i = 0; i < ARRAY_SIZE(features); i++) {
>  		fwft->configs[i].flags = 0;
> +		feature = &features[i];
> +		if (feature->reset)
> +			feature->reset(vcpu);
> +	}
>  }
>  
>  const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_fwft = {
> -- 
> 2.43.0
>

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