Re: [PATCH] target/i386: Introduce SapphireRapids-v3 to add missing features

[Daniel P . Berrangé]

On Wed, Apr 24, 2024 at 04:33:11PM +0800, Zhao Liu wrote:
> Hi Lei,
> 
> On Wed, Apr 24, 2024 at 03:29:12AM -0400, Lei Wang wrote:
> > Date: Wed, 24 Apr 2024 03:29:12 -0400
> > From: Lei Wang <lei4.wang@intel.com>
> > Subject: [PATCH] target/i386: Introduce SapphireRapids-v3 to add missing
> >  features
> > X-Mailer: git-send-email 2.39.3
> > 
> > Add the missing features(ss, tsc-adjust, cldemote, movdiri, movdir64b) in
> > the SapphireRapids-v3 CPU model.
> 
> Considering that these are missing features, not hardware updates/fixes/Linux
> support changes, then as opposed to adding v3, it would be more appropriate
> to add these flags directly to the v1 SPR model with Fixes tag (Fixes:
> commit 7eb061b06e97 ("i386: Add new CPU model SapphireRapids")).

That would break compatibility with v1 CPU models from existing releases
of QEMU. Once released, a CPU version is read-only to preserve compatibility,
which is why we have the CPU versioning concept. 

With regards,
Daniel
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