linux-kernel - Re: [PATCH RESEND v2 01/12] KVM: arm64: RMI: Export kvm_has_da

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Message-ID: <20251029163906.000041e2@huawei.com>
Date: Wed, 29 Oct 2025 16:39:06 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@...nel.org>
CC: <linux-coco@...ts.linux.dev>, <kvmarm@...ts.linux.dev>,
	<linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<dan.j.williams@...el.com>, <aik@....com>, <lukas@...ner.de>, Samuel Ortiz
	<sameo@...osinc.com>, Xu Yilun <yilun.xu@...ux.intel.com>, Jason Gunthorpe
	<jgg@...pe.ca>, Suzuki K Poulose <Suzuki.Poulose@....com>, Steven Price
	<steven.price@....com>, Bjorn Helgaas <helgaas@...nel.org>, Catalin Marinas
	<catalin.marinas@....com>, Marc Zyngier <maz@...nel.org>, Will Deacon
	<will@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>
Subject: Re: [PATCH RESEND v2 01/12] KVM: arm64: RMI: Export
 kvm_has_da_feature

On Mon, 27 Oct 2025 15:25:51 +0530
"Aneesh Kumar K.V (Arm)" <aneesh.kumar@...nel.org> wrote:

Hi Aneesh,

Great to see this support - this review might be a little superficial as
I think it's first time I've looked at this and I'll be getting my head around
it whilst reviewing.

Small process thing:
Always include a stand alone description in here.  Some git clients
don't put the patch title near the commit text. Add something like

Export kvm_has_da_feature() for use in later patches.

> This will be used in later patches
Patch title made me think this was exporting something that already existed.
Probably better to say  Add kvm_has_da_feature() helper for use in later patches
or something like that.

> 
> Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@...nel.org>
> ---
>  arch/arm64/include/asm/kvm_rmi.h | 1 +
>  arch/arm64/include/asm/rmi_smc.h | 1 +
>  arch/arm64/kvm/rmi.c             | 6 ++++++
>  3 files changed, 8 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/kvm_rmi.h b/arch/arm64/include/asm/kvm_rmi.h
> index 1b2cdaac6c50..a967061af6ed 100644
> --- a/arch/arm64/include/asm/kvm_rmi.h
> +++ b/arch/arm64/include/asm/kvm_rmi.h
> @@ -90,6 +90,7 @@ u32 kvm_realm_ipa_limit(void);
>  u32 kvm_realm_vgic_nr_lr(void);
>  u8 kvm_realm_max_pmu_counters(void);
>  unsigned int kvm_realm_sve_max_vl(void);
> +bool kvm_has_da_feature(void);
>  
>  u64 kvm_realm_reset_id_aa64dfr0_el1(const struct kvm_vcpu *vcpu, u64 val);
>  
> diff --git a/arch/arm64/include/asm/rmi_smc.h b/arch/arm64/include/asm/rmi_smc.h
> index 1000368f1bca..2ea657a87402 100644
> --- a/arch/arm64/include/asm/rmi_smc.h
> +++ b/arch/arm64/include/asm/rmi_smc.h
> @@ -87,6 +87,7 @@ enum rmi_ripas {
>  #define RMI_FEATURE_REGISTER_0_GICV3_NUM_LRS	GENMASK(37, 34)
>  #define RMI_FEATURE_REGISTER_0_MAX_RECS_ORDER	GENMASK(41, 38)
>  #define RMI_FEATURE_REGISTER_0_Reserved		GENMASK(63, 42)
> +#define RMI_FEATURE_REGISTER_0_DA		BIT(42)

Guess you want to be updating Reserved as seems bit 42 isn't any more.

>  
>  #define RMI_REALM_PARAM_FLAG_LPA2		BIT(0)
>  #define RMI_REALM_PARAM_FLAG_SVE		BIT(1)
> diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c
> index 478a73e0b35a..08f3d2362dfd 100644
> --- a/arch/arm64/kvm/rmi.c
> +++ b/arch/arm64/kvm/rmi.c
> @@ -1738,6 +1738,12 @@ int kvm_init_realm_vm(struct kvm *kvm)
>  	return 0;
>  }
>  
> +bool kvm_has_da_feature(void)
> +{
> +	return rmi_has_feature(RMI_FEATURE_REGISTER_0_DA);
> +}
> +EXPORT_SYMBOL_GPL(kvm_has_da_feature);
> +
>  void kvm_init_rmi(void)
>  {
>  	/* Only 4k page size on the host is supported */