linux-kernel - Re: [PATCH 2/5] irqchip/gic-v5: Populate struct gic_kvm

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Message-ID: <aFlvW2FNCyCi3h3Y@lpieralisi>
Date: Mon, 23 Jun 2025 17:14:35 +0200
From: Lorenzo Pieralisi <lpieralisi@...nel.org>
To: Sascha Bischoff <Sascha.Bischoff@....com>
Cc: "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	"kvmarm@...ts.linux.dev" <kvmarm@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, nd <nd@....com>,
	"maz@...nel.org" <maz@...nel.org>,
	"oliver.upton@...ux.dev" <oliver.upton@...ux.dev>,
	Joey Gouly <Joey.Gouly@....com>,
	Suzuki Poulose <Suzuki.Poulose@....com>,
	"yuzenghui@...wei.com" <yuzenghui@...wei.com>,
	"will@...nel.org" <will@...nel.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	Timothy Hayes <Timothy.Hayes@....com>
Subject: Re: [PATCH 2/5] irqchip/gic-v5: Populate struct gic_kvm_info

On Fri, Jun 20, 2025 at 04:07:51PM +0000, Sascha Bischoff wrote:
> Populate the gic_kvm_info struct based on support for
> FEAT_GCIE_LEGACY.  The struct is used by KVM to probe for a compatible
> GIC.
> 
> Co-authored-by: Timothy Hayes <timothy.hayes@....com>
> Signed-off-by: Timothy Hayes <timothy.hayes@....com>
> Signed-off-by: Sascha Bischoff <sascha.bischoff@....com>
> ---
>  drivers/irqchip/irq-gic-v5.c          | 34 +++++++++++++++++++++++++++
>  include/linux/irqchip/arm-vgic-info.h |  4 ++++
>  2 files changed, 38 insertions(+)
> 
> diff --git a/drivers/irqchip/irq-gic-v5.c b/drivers/irqchip/irq-gic-v5.c
> index 28853d51a2ea..6aecd2343fee 100644
> --- a/drivers/irqchip/irq-gic-v5.c
> +++ b/drivers/irqchip/irq-gic-v5.c
> @@ -13,6 +13,7 @@
>  
>  #include <linux/irqchip.h>
>  #include <linux/irqchip/arm-gic-v5.h>
> +#include <linux/irqchip/arm-vgic-info.h>
>  
>  #include <asm/cpufeature.h>
>  #include <asm/exception.h>
> @@ -1049,6 +1050,37 @@ static void gicv5_set_cpuif_idbits(void)
>  	}
>  }
>  
> +#ifdef CONFIG_KVM
> +static struct gic_kvm_info gic_v5_kvm_info __initdata;
> +
> +static bool gicv5_cpuif_has_gcie_legacy(void)

__init ?

> +{
> +	u64 idr0 = read_sysreg_s(SYS_ICC_IDR0_EL1);
> +
> +	return !!FIELD_GET(ICC_IDR0_EL1_GCIE_LEGACY, idr0);
> +}
> +
> +static void __init gic_of_setup_kvm_info(struct device_node *node)
> +{
> +	gic_v5_kvm_info.type = GIC_V5;
> +	gic_v5_kvm_info.has_gcie_v3_compat = gicv5_cpuif_has_gcie_legacy();
> +
> +	/* GIC Virtual CPU interface maintenance interrupt */
> +	gic_v5_kvm_info.no_maint_irq_mask = false;
> +	gic_v5_kvm_info.maint_irq = irq_of_parse_and_map(node, 0);
> +	if (!gic_v5_kvm_info.maint_irq) {
> +		pr_warn("cannot find GICv5 virtual CPU interface maintenance interrupt\n");
> +		return;
> +	}
> +
> +	vgic_set_kvm_info(&gic_v5_kvm_info);
> +}
> +#else
> +static void __init gic_of_setup_kvm_info(struct device_node *node)

static inline

Thanks,
Lorenzo

> +{
> +}
> +#endif // CONFIG_KVM
> +
>  static int __init gicv5_of_init(struct device_node *node, struct device_node *parent)
>  {
>  	int ret = gicv5_irs_of_probe(node);
> @@ -1081,6 +1113,8 @@ static int __init gicv5_of_init(struct device_node *node, struct device_node *pa
>  
>  	gicv5_irs_its_probe();
>  
> +	gic_of_setup_kvm_info(node);
> +
>  	return 0;
>  out_int:
>  	gicv5_cpu_disable_interrupts();
> diff --git a/include/linux/irqchip/arm-vgic-info.h b/include/linux/irqchip/arm-vgic-info.h
> index a75b2c7de69d..ca1713fac6e3 100644
> --- a/include/linux/irqchip/arm-vgic-info.h
> +++ b/include/linux/irqchip/arm-vgic-info.h
> @@ -15,6 +15,8 @@ enum gic_type {
>  	GIC_V2,
>  	/* Full GICv3, optionally with v2 compat */
>  	GIC_V3,
> +	/* Full GICv5, optionally with v3 compat */
> +	GIC_V5,
>  };
>  
>  struct gic_kvm_info {
> @@ -34,6 +36,8 @@ struct gic_kvm_info {
>  	bool		has_v4_1;
>  	/* Deactivation impared, subpar stuff */
>  	bool		no_hw_deactivation;
> +	/* v3 compat support (GICv5 hosts, only) */
> +	bool		has_gcie_v3_compat;
>  };
>  
>  #ifdef CONFIG_KVM
> -- 
> 2.34.1