target-i386: Don't try to enable PT State xsave component
The code that calculates the set of supported XSAVE components on CPUID looks at ext_save_areas to find out which components should be enabled. However, if there are zeroed entries in the ext_save_areas array, the ((env->features[esa->feature] & esa->bits) == esa->bits) check will always succeed and QEMU will unconditionally try to enable the component. Luckily this never caused any problems because the only missing entry in ext_save_areas is the PT State component (bit 8), and KVM currently doesn't support it (so it was cleared on ena_mask). But the code was still incorrect and would break if KVM starts returning CPUID[EAX=0xD,ECX=0].EAX[bit 8] as supported on GET_SUPPORTED_CPUID. Fix the problem by changing the code to not enable a XSAVE component if ExtSaveArea::bits is zero. Reviewed-by: NRichard Henderson <rth@twiddle.net> Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>
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