Subject: Re: [PATCH v6 14/39] KVM: arm64: gic-v5: Trap and emulate ICC_IDR0_EL1 accesses

From: Jonathan Cameron <[email-masked]>
Date: Thu, 19 Mar 2026 10:38:26 +0000

On Tue, 17 Mar 2026 11:43:34 +0000
Sascha Bischoff <[email-masked]> wrote:

> Unless accesses to the ICC_IDR0_EL1 are trapped by KVM, the guest
> reads the same state as the host. This isn't desirable as it limits
> the migratability of VMs and means that KVM can't hide hardware
> features such as FEAT_GCIE_LEGACY.
> 
> Trap and emulate accesses to the register, and present KVM's chosen ID
> bits and Priority bits (which is 5, as GICv5 only supports 5 bits of
> priority in the CPU interface). FEAT_GCIE_LEGACY is never presented to
> the guest as it is only relevant for nested guests doing mixed GICv5
> and GICv3 support.
> 
> Signed-off-by: Sascha Bischoff <[email-masked]>
Does what I'd expect.

Reviewed-by: Jonathan Cameron <[email-masked]>