Re: [Qemu-devel] [PATCH 0/4] target-i386: Don't try to enable unsupported TCG features by default

[Eduardo Habkost]

On Fri, Sep 11, 2015 at 12:32:35PM -0700, Richard Henderson wrote:
> On 09/11/2015 12:25 PM, Eduardo Habkost wrote:
> > This series makes QEMU stop trying to enable an unsupported feature by 
> > default
> > in TCG mode, avoiding the warnings shown by the (now enabled by default)
> > "check" mode.
> > 
> > To do that, I cchanged the kvm_default_features code to be based on QOM
> > properties, and added a new "type" field to allow per-CPU-model KVM 
> > defaults to
> > be specified.
> > 
> > Before this series:
> > 
> >   $ qemu-system-x86_64 -S
> >   warning: TCG doesn't support requested feature: CPUID.01H:EDX.de [bit 2]
> >   warning: TCG doesn't support requested feature: CPUID.80000001H:EDX [bit 
> > 2]
> > 
> > After this series:
> > 
> >   $ ./x86_64-softmmu/qemu-system-x86_64 -S
> >   [no warning output]
> 
> Wouldn't it be easier simply to implement this bit?
> It seems like we're simply creating a compatibility mess otherwise.

I don't think the compatibility mess is worse than the one we already
have with x2apic. I even think the new type/property/value system is
cleaner than the existing kvm_default_*features arrays.

About implementing DE in TCG: I really don't think it is easier, but if
somebody wants to implement it, it would be welcome.

-- 
Eduardo