Re: [PATCH v4 3/3] arm/kvm: get demuxed ID registers from kvm

[Sebastian Ott <sebott@redhat.com>]

Hej Eric,

On Tue, 7 Jul 2026, Eric Auger wrote:
> On 7/2/26 3:36 PM, Sebastian Ott wrote:
>> From: Cornelia Huck <cohuck@redhat.com>
>>
>> We now have the infrastructure in place to handle demuxed ID registers
>> from kvm. Use it to get the values that kvm emulates for CCSIDR_EL1.
>
> I wonder whether that patch is needed at this point. Were previous
> ccsidr[i] initialized from KVM before? What is the actual motivation to
> read them in this series. Doesn't it bring the risk to expose new values
> to the guest?
>
> For instance, in [RFC PATCH v6 11/17] arm/kvm: Initialize all writable
> ID registers from host, I generalized the initialization of all writable
> id regs and I noticed that the new initialization of CLIDR from KVM
> broke the execution (which is not the case for the CCSIDR because I did
> it a try) because CLIDR was previously uninitialized and null.

The issue is holes in arm64_id_regs[] and we stumble over that in
get_host_cpu_idregs(). Maybe we could skip the demuxed regs when we
iterate over that array.

Sebastian