On Fri, Sep 18, 2009 at 12:02 PM, Samuel Bronson <[email protected]> wrote:
> On Wed, Sep 16, 2009 at 7:59 AM, SINGER Bernd NLTD-G (AREVA NP GmbH)
> <[email protected]> wrote:
>
>> But how about evaluating the cpu flag needed by dosemu?
>> this prevents dosemu from carrying a list of cpu families.
>> Currently i have no patch - i dont know the cpu flags needed by dosemu.
>> Is there someone who can do this?

SVN since April has a simple check:
if (k > 5) k = 5;

and then it looks at the cpuid flags to determine what is available.

The code was originally there to avoid passing a too high CPU type
from $_cpu to vm86, that is
for 386/486/586 processors. After that it doesn't matter, however the
way the code worked it didn't support unknown CPUs (instead of
assuming they'd be future more powerful CPUs).

> Certainly, using the feature flags is a far more appropriate approach
> than maintaining a list of CPU types known to work, and not at least
> having a list of them would be (is?) VERY bad -- assuming, of course,
> that the features needed *have* flags. Using the Linux-specific
> information from /proc/cpuinfo may or may not be the best way to do it
> (of course, the CPU-provided flags will not tell us things like
> f00f_bug...), depending on whether we want dosemu to work on anything
> but Linux (and on what other systems it works (or could easily be made
> to work) on right now).

Yes certainly avoiding /proc/cpuinfo and using CPUID directly instead
is more portable.
A few CPUID features are checked for: prefetch (mmxext/sse) for
cpuemu, tsc for rdtsc, and fxsr for SSE fxsave (these are all standard
on x86-64 though).

Bart

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