Re: [PATCH v5 19/49] KVM: arm64: gic-v5: Add KVM_VGIC_V5_ADDR_TYPE_IRS to UAPI

[Sascha Bischoff <Sascha.Bischoff@arm.com>]

On Fri, 2026-08-07 at 14:27 +0000, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 2 potential
> issue(s) to consider:
> - [High] The patch defines the UAPI constant
> KVM_VGIC_V5_ADDR_TYPE_IRS for userspace to specify the IRS location,
> but provides no corresponding kernel implementation to handle it.
> - [Low] The newly added UAPI macro KVM_VGIC_V5_IRS_SIZE uses the
> kernel-internal macro SZ_64K, which is not exported to userspace and
> will cause compilation errors.
> --
> 
> --- Patch [19]: [PATCH v5 19/49] KVM: arm64: gic-v5: Add
> KVM_VGIC_V5_ADDR_TYPE_IRS to UAPI ---
> commit 2deebb3b97ce3e2f88f0cdf0452104edbd0a7ea6
> Author: Sascha Bischoff <Sascha.Bischoff@arm.com>
> 
> KVM: arm64: gic-v5: Add KVM_VGIC_V5_ADDR_TYPE_IRS to UAPI
> 
> This patch adds the UAPI definitions for the GICv5 IRS address type
> and size 
> to the arm64 KVM headers. It reserves 2x64kB in the GPA space for the
> IRS 
> CONFIG_FRAME and SETLPI_FRAME.
> 
> > diff --git a/arch/arm64/include/uapi/asm/kvm.h
> > b/arch/arm64/include/uapi/asm/kvm.h
> > index 1c13bfa2d38aa..d1b2ca317f586 100644
> > --- a/arch/arm64/include/uapi/asm/kvm.h
> > +++ b/arch/arm64/include/uapi/asm/kvm.h
> [ ... ]
> > @@ -97,6 +97,11 @@ struct kvm_regs {
> >  #define KVM_VGIC_V3_REDIST_SIZE		(2 * SZ_64K)
> >  #define KVM_VGIC_V3_ITS_SIZE		(2 * SZ_64K)
> >  
> > +/* Supported VGICv5 address types  */
> > +#define KVM_VGIC_V5_ADDR_TYPE_IRS	6
> > +
> 
> [Severity: High]
> Does this patch provide the kernel implementation to handle
> KVM_VGIC_V5_ADDR_TYPE_IRS?

No, it does not.

> 
> If userspace attempts to use this UAPI definition with the
> KVM_DEV_ARM_VGIC_GRP_ADDR attribute group, vgic_v5_set_attr()
> explicitly
> returns -ENXIO for that group:
> 
> arch/arm64/kvm/vgic/vgic-kvm-device.c:vgic_v5_set_attr() {
> 	switch (attr->group) {
> 	case KVM_DEV_ARM_VGIC_GRP_ADDR:
> 	case KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS:
> 	case KVM_DEV_ARM_VGIC_GRP_NR_IRQS:
> 		return -ENXIO;
> ...
> }
> 
> Similarly, kvm_vgic_addr() lacks a case for KVM_VGIC_V5_ADDR_TYPE_IRS
> and
> would reject it with -ENODEV:
> 
> arch/arm64/kvm/vgic/vgic-kvm-device.c:kvm_vgic_addr() {
> ...
> 	default:
> 		r = -ENODEV;
> 	}
> ...
> }
> 
> Without handling in the kernel, userspace cannot configure the base
> address
> of the GICv5 IRS, which renders the GICv5 IRS emulation feature
> unusable.

See next commits in series.

> 
> > +#define KVM_VGIC_V5_IRS_SIZE		(2 * SZ_64K)
> > +
> 
> [Severity: Low]
> Does this newly added UAPI definition rely on the kernel-internal
> macro
> SZ_64K?

This matches the existing defines for GICv3. I don't think that this is
an issue.

> 
> Since <linux/sizes.h> is not exported to userspace, userspace
> programs
> attempting to use KVM_VGIC_V5_IRS_SIZE will fail to compile with an
> undeclared identifier error for SZ_64K.
> 
> While this pattern already exists in the file for GICv3 sizes,
> introducing a
> new instance perpetuates the UAPI breakage.
> 
> >  #define KVM_ARM_VCPU_POWER_OFF		0 /* CPU is started in OFF
> > state */
> >  #define KVM_ARM_VCPU_EL1_32BIT		1 /* CPU running a 32bit
> > VM */
> >  #define KVM_ARM_VCPU_PSCI_0_2		2 /* CPU uses PSCI v0.2 */
> > diff --git a/tools/arch/arm64/include/uapi/asm/kvm.h
> > b/tools/arch/arm64/include/uapi/asm/kvm.h
> > index 1c13bfa2d38aa..d1b2ca317f586 100644
> > --- a/tools/arch/arm64/include/uapi/asm/kvm.h
> > +++ b/tools/arch/arm64/include/uapi/asm/kvm.h
> [ ... ]
> > @@ -97,6 +97,11 @@ struct kvm_regs {
> >  #define KVM_VGIC_V3_REDIST_SIZE		(2 * SZ_64K)
> >  #define KVM_VGIC_V3_ITS_SIZE		(2 * SZ_64K)
> >  
> > +/* Supported VGICv5 address types  */
> > +#define KVM_VGIC_V5_ADDR_TYPE_IRS	6
> > +
> > +#define KVM_VGIC_V5_IRS_SIZE		(2 * SZ_64K)
> > +
> 
> [Severity: Low]
> Are the same SZ_64K and missing implementation issues applicable to
> this
> mirrored tools UAPI header?

See above.

> 
> >  #define KVM_ARM_VCPU_POWER_OFF		0 /* CPU is started in OFF
> > state */
> >  #define KVM_ARM_VCPU_EL1_32BIT		1 /* CPU running a 32bit
> > VM */
> >  #define KVM_ARM_VCPU_PSCI_0_2		2 /* CPU uses PSCI v0.2 */
> 

Thanks,
Sascha