Re: [Qemu-devel] [PATCH] i386/cpu: name new CPUID bits

[Eduardo Habkost]

On Fri, Oct 19, 2012 at 01:34:19AM +0200, Andre Przywara wrote:
> On 10/18/12 18:33, Eduardo Habkost wrote:
> >On Wed, Oct 17, 2012 at 11:17:26PM +0200, Andre Przywara wrote:
> >>Update QEMU's knowledge of CPUID bit names. This allows to
> >>enable/disable those new features on QEMU's command line when
> >>using KVM and prepares future feature enablement in QEMU.
> ...
> >>@@ -79,10 +79,10 @@ static const char *ext3_feature_name[] = {
> >>      "lahf_lm" /* AMD LahfSahf */, "cmp_legacy", "svm", "extapic" /* AMD 
> >> ExtApicSpace */,
> >>      "cr8legacy" /* AMD AltMovCr8 */, "abm", "sse4a", "misalignsse",
> >>      "3dnowprefetch", "osvw", "ibs", "xop",
> >>-    "skinit", "wdt", NULL, NULL,
> >>-    "fma4", NULL, "cvt16", "nodeid_msr",
> >>-    NULL, NULL, NULL, NULL,
> >>-    NULL, NULL, NULL, NULL,
> >>+    "skinit", "wdt", NULL, "lwp",
> >>+    "fma4", "tce", NULL, "nodeid_msr",
> >
> >You removed cvt16, here.
> 
> On purpose, cvt16 is dead. It seems to have been advertised in the
> documentation for some time, but later disappeared. The respective
> instructions are now reported via the F16C flag in the Intel leaf.
> 
> If you want to know more, I can dig deeper and ask some people. But
> the bit is now "reserved" and was never '1' in any silicon. (And was
> introduced by me into QEMU :-(

KVM doesn't report it on GET_SUPPORTED_CPUID, either, so it's impossible
to have any VM running with that bit set, even if was set on some
silicon.

It would be interesting to document that on the commit message, though.

> 
> >
> >All the rest of the flags look OK to me.
> 
> Thanks.
> 
> Regards,
> Andre.
> 
> 

-- 
Eduardo