[Xen-devel] RE: Solaris and PVRDTSCP

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

Hi Paul --

> From: Paul Durrant [mailto:Paul.Durrant@xxxxxxxxxx]
> Cc: Dan Magenheimer
> Subject: Solaris and PVRDTSCP
> 
> Hi,
> 
>   I've been trying to figure out why my copy of s10u9 did not run PV drivers 
> when I installed it on
> Xen 4.1 when it was perfectly happy on Xen 3.4...
> 
>   It turns out that the kernel is making a check that the maximal Xen CPUID 
> leaf is no greater than
> base + 2. This was true on Xen 3.4 but when the PVRDTSCP patch was added it 
> ceased to be true with the
> addition of the cpuid_time_leaf code.

What happens?  Belly up?  Why is this only on PV drivers rather than pure HVM?

>   Clearly future versions of the Solaris kernel should revise this check but 
> to allow this kernel to
> enable PV drivers I was wondering what sort of workaround could be done. My 
> current thoughts are along
> the lines of disabling the extra CPUID leaf if tsc_mode is < 
> TSC_MODE_PVRDTSCP.

This seems reasonable.  The info on that leaf could be useful in other
modes, but likely hasn't been.

> An alternative might
> be to introduce another tsc_mode that specifically causes the leaf to be 
> obscured. Thoughts?
> 
>   Paul

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