Patchwork [v2,4/4] arm: Auto-detect guest GIC type

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Submitter Andre Przywara
Date Feb. 1, 2019, 12:37 p.m.
Message ID <20190201123716.92901-5-andre.przywara@arm.com>
Download mbox | patch
Permalink /patch/715751/
State New
Headers show

Comments

Andre Przywara - Feb. 1, 2019, 12:37 p.m.
At the moment kvmtool always tries to instantiate a virtual GICv2 for
the guest, and fails with some scary error message if that doesn't work.
The user has then to manually specify "--irqchip=gicv3", which is not
really obvious.
With the advent of more GICv3-only machines, let's try to be more
clever and implement some auto-detection of the GIC type needed:
We try gicv3-its, gicv3, gicv2m and gicv2, in that order. That first one
succeeding wins.
For GICv2 machines the first two will always fail. For GICv2-backwards
compatible GICv3 machines GICv3 is probably the better choice these days.

This algorithm is in effect is there is no explicit --irqchip parameter
on the command line. We still allow the GIC type to be set explicitly.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
 arm/gic.c                    | 25 +++++++++++++++++++++++++
 arm/include/arm-common/gic.h |  1 +
 2 files changed, 26 insertions(+)
Will Deacon - Feb. 8, 2019, 4:10 p.m.
On Fri, Feb 01, 2019 at 12:37:16PM +0000, Andre Przywara wrote:
> At the moment kvmtool always tries to instantiate a virtual GICv2 for
> the guest, and fails with some scary error message if that doesn't work.
> The user has then to manually specify "--irqchip=gicv3", which is not
> really obvious.
> With the advent of more GICv3-only machines, let's try to be more
> clever and implement some auto-detection of the GIC type needed:
> We try gicv3-its, gicv3, gicv2m and gicv2, in that order. That first one
> succeeding wins.
> For GICv2 machines the first two will always fail. For GICv2-backwards
> compatible GICv3 machines GICv3 is probably the better choice these days.
> 
> This algorithm is in effect is there is no explicit --irqchip parameter
> on the command line. We still allow the GIC type to be set explicitly.
> 
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
>  arm/gic.c                    | 25 +++++++++++++++++++++++++
>  arm/include/arm-common/gic.h |  1 +
>  2 files changed, 26 insertions(+)
> 
> diff --git a/arm/gic.c b/arm/gic.c
> index abcbcc09..a86da20e 100644
> --- a/arm/gic.c
> +++ b/arm/gic.c
> @@ -182,6 +182,8 @@ static int gic__create_device(struct kvm *kvm, enum irqchip_type type)
>  		gic_device.type = KVM_DEV_TYPE_ARM_VGIC_V3;
>  		dist_attr.attr  = KVM_VGIC_V3_ADDR_TYPE_DIST;
>  		break;
> +	case IRQCHIP_AUTO:
> +		return -ENODEV;
>  	}
>  
>  	err = ioctl(kvm->vm_fd, KVM_CREATE_DEVICE, &gic_device);
> @@ -199,6 +201,8 @@ static int gic__create_device(struct kvm *kvm, enum irqchip_type type)
>  	case IRQCHIP_GICV3:
>  		err = ioctl(gic_fd, KVM_SET_DEVICE_ATTR, &redist_attr);
>  		break;
> +	case IRQCHIP_AUTO:
> +		return -ENODEV;
>  	}
>  	if (err)
>  		goto out_err;
> @@ -249,9 +253,30 @@ static int gic__create_irqchip(struct kvm *kvm)
>  
>  int gic__create(struct kvm *kvm, enum irqchip_type type)
>  {
> +	enum irqchip_type try;
>  	int err;
>  
>  	switch (type) {
> +	case IRQCHIP_AUTO:
> +		try = IRQCHIP_GICV3_ITS;
> +		err = gic__create(kvm, try);
> +		if (err) {
> +			try = IRQCHIP_GICV3;
> +			err = gic__create(kvm, try);
> +		}
> +		if (err) {
> +			try = IRQCHIP_GICV2M;
> +			err = gic__create(kvm, try);
> +		}
> +		if (err) {
> +			try = IRQCHIP_GICV2;
> +			err = gic__create(kvm, try);
> +		}
> +		if (err)
> +			return err;

Easier to write this as a descending loop over the irqchip_type enum?

Will

Patch

diff --git a/arm/gic.c b/arm/gic.c
index abcbcc09..a86da20e 100644
--- a/arm/gic.c
+++ b/arm/gic.c
@@ -182,6 +182,8 @@  static int gic__create_device(struct kvm *kvm, enum irqchip_type type)
 		gic_device.type = KVM_DEV_TYPE_ARM_VGIC_V3;
 		dist_attr.attr  = KVM_VGIC_V3_ADDR_TYPE_DIST;
 		break;
+	case IRQCHIP_AUTO:
+		return -ENODEV;
 	}
 
 	err = ioctl(kvm->vm_fd, KVM_CREATE_DEVICE, &gic_device);
@@ -199,6 +201,8 @@  static int gic__create_device(struct kvm *kvm, enum irqchip_type type)
 	case IRQCHIP_GICV3:
 		err = ioctl(gic_fd, KVM_SET_DEVICE_ATTR, &redist_attr);
 		break;
+	case IRQCHIP_AUTO:
+		return -ENODEV;
 	}
 	if (err)
 		goto out_err;
@@ -249,9 +253,30 @@  static int gic__create_irqchip(struct kvm *kvm)
 
 int gic__create(struct kvm *kvm, enum irqchip_type type)
 {
+	enum irqchip_type try;
 	int err;
 
 	switch (type) {
+	case IRQCHIP_AUTO:
+		try = IRQCHIP_GICV3_ITS;
+		err = gic__create(kvm, try);
+		if (err) {
+			try = IRQCHIP_GICV3;
+			err = gic__create(kvm, try);
+		}
+		if (err) {
+			try = IRQCHIP_GICV2M;
+			err = gic__create(kvm, try);
+		}
+		if (err) {
+			try = IRQCHIP_GICV2;
+			err = gic__create(kvm, try);
+		}
+		if (err)
+			return err;
+
+		kvm->cfg.arch.irqchip = try;
+		return 0;
 	case IRQCHIP_GICV2M:
 		gic_msi_size = KVM_VGIC_V2M_SIZE;
 		gic_msi_base = ARM_GIC_CPUI_BASE - gic_msi_size;
diff --git a/arm/include/arm-common/gic.h b/arm/include/arm-common/gic.h
index 1125d601..ec9cf31a 100644
--- a/arm/include/arm-common/gic.h
+++ b/arm/include/arm-common/gic.h
@@ -24,6 +24,7 @@ 
 #define KVM_VGIC_V2M_SIZE		0x1000
 
 enum irqchip_type {
+	IRQCHIP_AUTO,
 	IRQCHIP_GICV2,
 	IRQCHIP_GICV2M,
 	IRQCHIP_GICV3,