Re: [RFC 21/21] arm/cpu-features: Document custom vcpu model

["Daniel P. Berrangé" <berrange@redhat.com>]

On Fri, Oct 25, 2024 at 03:28:35PM +0200, Eric Auger wrote:
> Hi Daniel,
> 
> On 10/25/24 15:13, Daniel P. Berrangé wrote:
> > On Fri, Oct 25, 2024 at 12:17:40PM +0200, Eric Auger wrote:
> >> From: Cornelia Huck <cohuck@redhat.com>
> >>
> >> Add some documentation for the custom model.
> >>
> >> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> >> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> >> ---
> >>  docs/system/arm/cpu-features.rst | 55 +++++++++++++++++++++++++++-----
> >>  1 file changed, 47 insertions(+), 8 deletions(-)
> >
> >> @@ -167,6 +196,16 @@ disabling many SVE vector lengths would be quite verbose, the ``sve<N>`` CPU
> >>  properties have special semantics (see "SVE CPU Property Parsing
> >>  Semantics").
> >>  
> >> +The ``custom`` CPU model needs to be configured via individual ID register
> >> +field properties, for example::
> >> +
> >> +  $ qemu-system-aarch64 -M virt -cpu custom,SYSREG_ID_AA64ISAR0_EL1_DP=0x0
> >> +
> >> +This forces ID_AA64ISAR0_EL1 DP field to 0.
> > What is the "baseline" featureset implied by 'custom' ?
> there is no baseline at the moment. By default this is a host
> passthrough model.

Why do we need to create "custom" at all, as opposed to just letting
users toggle features on "-cpu host" ? 

With regards,
Daniel
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