Re: [Xen-devel] write_tsc in a PV domain?

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 26/08/2009 16:42, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

> OK, I see, wrmsr_hypervisor_regs(0x10) and mce_wrmsr(0x10) and
> rdmsr_safe(0x10) all return 0, so the code at "invalid:" is
> executed and a warning is printk'd.  So in the current
> implementation, write_tsc is skipped over.
> 
> But ARCHITECTURALLY does Xen consider write_tsc to be a no-op
> for PV domains, or is this just a case that's never been
> encountered before?  In other words, if a future PV OS had a
> good reason to write_tsc, would we implement it (and make
> the necessary adjustments to Xen's usages of tsc) or just say,
> sorry, not allowed?

There'd have to be a good argument for supporting it. I don't think we ever
will.

 -- Keir



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