From: Suzuki K Poulose <suzuki.poulose@arm.com>
To: sashiko-reviews@lists.linux.dev
Cc: Oliver Upton <oupton@kernel.org>,
kvmarm@lists.linux.dev, kvm@vger.kernel.org,
Marc Zyngier <maz@kernel.org>, Fuad Tabba <tabba@google.com>
Subject: Re: [PATCH v21 18/23] KVM: arm64: CCA: Don't expose unsupported capabilities for realm guests
Date: Fri, 2 Oct 2026 10:20:30 +0100 [thread overview]
Message-ID: <73ee7e2e-997b-4b19-9280-2d5a5d5c8deb@arm.com> (raw)
In-Reply-To: <20261002091348.1769C1F00899@smtp.kernel.org>
On 02/10/2026 10:13, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Medium] arm64: kvm: KVM_CAP_IRQCHIP incorrectly exposed for Realm VMs
> --
>
> commit af0bceb4971b2a4c5816fbca6500c4f10a51388d
> Author: Suzuki K Poulose <suzuki.poulose@arm.com>
>
> KVM: arm64: CCA: Don't expose unsupported capabilities for realm guests
>
> This commit limits the capabilities that are allowed for Realm VMs and blocks
> the corresponding vm_ioctls. It repurposes kvm_pkvm_ioctl_allowed() to
> support both pKVM and Realm ioctls and adds a generic kvm_vm_ext_allowed()
> helper for filtering.
>
>> diff --git a/arch/arm64/include/asm/kvm_rmi.h b/arch/arm64/include/asm/kvm_rmi.h
>> index 44f5c75a27b5b..ea1450e0c8619 100644
>> --- a/arch/arm64/include/asm/kvm_rmi.h
>> +++ b/arch/arm64/include/asm/kvm_rmi.h
> [ ... ]
>> @@ -58,4 +60,26 @@ struct realm {
>>
>> void kvm_init_rmi(void);
>>
>> +static inline bool kvm_realm_ext_allowed(long ext)
>> +{
>> + switch (ext) {
>> + case KVM_CAP_IRQCHIP:
>
> [Severity: Medium]
> The commit message states "Drop KVM_CAP_CREATE_IRQCHIP, as we don't support
> VGIC_V2 for Realms". Did you intend to drop KVM_CAP_IRQCHIP from this
> allowlist?
No, this was put back in based on Fuad's comment to advertise that
in-kernel IRQ chip is supported.
See
https://lore.kernel.org/all/CA+EHjTwYqTFzGdNPproWW5L6j5pNqmuWeFuu9HbHa8LBLPvY2A@mail.gmail.com
Cheers
Suzuki
>
> Because KVM_CAP_IRQCHIP is still explicitly allowed here in
> kvm_realm_ext_allowed(), userspace is falsely advertised VGIC_V2 capability
> via KVM_CHECK_EXTENSION.
>
> This also allows the KVM_CREATE_IRQCHIP ioctl to bypass the
> kvm_vm_ioctl_allowed() check in kvm_arch_vm_ioctl() and attempt to
> instantiate an unsupported VGIC_V2 before being rejected downstream.
>
>> + case KVM_CAP_ARM_PSCI:
>> + case KVM_CAP_ARM_PSCI_0_2:
>> + case KVM_CAP_DEVICE_CTRL:
> [ ... ]
>
next prev parent reply other threads:[~2026-10-02 9:20 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-01 21:06 [PATCH v21 00/23] KVM: arm64: CCA: Add basic plumbing for Realms Suzuki K Poulose
2026-10-01 21:06 ` [PATCH v21 01/23] KVM: arm64: protected VM: Handle user writes to CNTVCT_EL0/CNTPCT_EL0 Suzuki K Poulose
2026-10-01 21:06 ` [PATCH v21 02/23] KVM: arm64: Disable Steal time accounting for protected guests Suzuki K Poulose
2026-10-01 21:06 ` [PATCH v21 03/23] KVM: arm64: Include kvm_emulate.h in kvm/arm_psci.h Suzuki K Poulose
2026-10-01 21:06 ` [PATCH v21 04/23] KVM: arm64: Avoid including linux/kvm_host.h in kvm_pgtable.h Suzuki K Poulose
2026-10-01 21:06 ` [PATCH v21 05/23] KVM: arm64: Track the type of VM in kvm_arch Suzuki K Poulose
2026-10-02 10:06 ` Fuad Tabba
2026-10-02 12:57 ` Marc Zyngier
2026-10-02 13:05 ` Fuad Tabba
2026-10-02 13:10 ` Suzuki K Poulose
2026-10-02 13:34 ` Marc Zyngier
2026-10-02 14:15 ` Marc Zyngier
2026-10-02 14:37 ` Fuad Tabba
2026-10-02 15:29 ` Marc Zyngier
2026-10-02 15:30 ` Fuad Tabba
2026-10-03 5:53 ` Suzuki K Poulose
2026-10-03 7:07 ` Suzuki K Poulose
2026-10-03 8:45 ` Marc Zyngier
2026-10-02 15:15 ` Suzuki K Poulose
2026-10-02 15:40 ` Marc Zyngier
2026-10-02 15:42 ` Suzuki K Poulose
2026-10-01 21:06 ` [PATCH v21 06/23] KVM: arm64: Don't call vcpu_set_pauth_traps for pKVM host Suzuki K Poulose
2026-10-01 21:06 ` [PATCH v21 07/23] KVM: arm64: Refactor the vcpu_load to allow for VM specific callbacks Suzuki K Poulose
2026-10-01 21:06 ` [PATCH v21 08/23] KVM: arm64: Add vcpu load/put call backs for flavors Suzuki K Poulose
2026-10-01 21:06 ` [PATCH v21 09/23] KVM: arm64: Reuse kvm_stage2_unmap_range in kvm_unmap_gfn_range Suzuki K Poulose
2026-10-01 21:06 ` [PATCH v21 10/23] KVM: arm64: Add VM specific callback for S2 MMU operations Suzuki K Poulose
2026-10-02 10:19 ` Fuad Tabba
2026-10-02 10:29 ` Suzuki K Poulose
2026-10-03 9:01 ` Marc Zyngier
2026-10-03 15:30 ` Suzuki K Poulose
2026-10-03 16:12 ` Suzuki K Poulose
2026-10-03 17:32 ` Marc Zyngier
2026-10-01 21:06 ` [PATCH v21 11/23] KVM: arm64: Use a local kvm pointer in kvm_handle_guest_abort() Suzuki K Poulose
2026-10-02 9:14 ` Fuad Tabba
2026-10-01 21:06 ` [PATCH v21 12/23] KVM: arm64: Abstract out memory abort handling Suzuki K Poulose
2026-10-01 21:06 ` [PATCH v21 13/23] KVM: arm64: Mandate VGIC v3 for pKVM VMs and Realms Suzuki K Poulose
2026-10-02 9:23 ` Fuad Tabba
2026-10-01 21:06 ` [PATCH v21 14/23] KVM: arm64: CCA: Add a new mode for supporting Realm guests Suzuki K Poulose
2026-10-01 21:06 ` [PATCH v21 15/23] KVM: arm64: CCA: Add VCPU load/put for Realms Suzuki K Poulose
2026-10-01 21:06 ` [PATCH v21 16/23] KVM: arm64: CCA: Add bare minimal S2 operations for Realm Suzuki K Poulose
2026-10-01 21:06 ` [PATCH v21 17/23] KVM: arm64: CCA: Introduce Realms Suzuki K Poulose
2026-10-01 21:06 ` [PATCH v21 18/23] KVM: arm64: CCA: Don't expose unsupported capabilities for realm guests Suzuki K Poulose
2026-10-02 9:13 ` sashiko-bot
2026-10-02 9:20 ` Suzuki K Poulose [this message]
2026-10-02 9:34 ` Fuad Tabba
2026-10-02 9:36 ` Suzuki K Poulose
2026-10-01 21:06 ` [PATCH v21 19/23] KVM: arm64: Prevent unsupported vcpu features for VM types Suzuki K Poulose
2026-10-01 21:07 ` [PATCH v21 20/23] KVM: arm64: CCA: WARN on injected undef exceptions Suzuki K Poulose
2026-10-01 21:07 ` [PATCH v21 21/23] KVM: arm64: CCA: Support timers in realm RECs Suzuki K Poulose
2026-10-01 21:07 ` [PATCH v21 22/23] KVM: arm64: CCA: Expose SVE VL register before VCPU finalization Suzuki K Poulose
2026-10-02 9:13 ` sashiko-bot
2026-10-01 21:07 ` [PATCH v21 23/23] KVM: arm64: CCA: Control user register access for Realms Suzuki K Poulose
2026-10-01 21:41 ` [PATCH v21 00/23] KVM: arm64: CCA: Add basic plumbing " Gavin Shan
2026-10-02 6:13 ` Suzuki K Poulose
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