Re: [Qemu-devel] question regarding odd CPU feature assignement

[Filip Navara]

It's not a typo. The short story is that there are two CPUID feature registers - 1/EDX and 0x80000001/EDX - that differ slightly. The later one was first used by AMD CPUs and mostly enhanced by adding new features to processors from the said company (3DNow and such). The first one was introduced by Intel and on AMD processor it's only used for compatibility, but not for AMD-specific extensions. You can learn more by looking at the tables on 
http://www.sandpile.org/ia32/cpuid.htm.

Best regards,
Filip Navara

On 9/10/07, Dan Kenigsberg <address@hidden> wrote:

Line 132 of qemu/target-i386/helper2.c has

        /* currently not enabled for std i386 because not fully tested */
        env->cpuid_ext2_features = (env->cpuid_features & 0x0183F3FF);

Which smells like a typo: I see no reason to make cpuid_ext2_features a
masked version of cpuid_features.

Would someone care to elaborate?

Thanks,

    Dan.