Re: [kvm-devel] [PATCH 3/3] Eliminate read_cr3 on TLB flush

[Rusty Russell <rusty@rustcorp.com.au>]

On Wed, 2007-05-30 at 14:22 -0500, Anthony Liguori wrote:
> I was actually thinking about adding a hypercall to set/clear a bit in a 
> control register.  The thought here is that it would be useful not just 
> for the global bit but also for CR0.TS although we would need another 
> paravirt_op hook for stts.

We don't really need one, because Linux (i386) only cares about the TS
bit of cr0.  From lguest (you'd want this per-cpu of course):

        static unsigned long current_cr0, current_cr3;
        static void lguest_write_cr0(unsigned long val)
        {
        	lazy_hcall(LHCALL_TS, val & 8, 0, 0);
        	current_cr0 = val;
        }
        
        static unsigned long lguest_read_cr0(void)
        {
        	return current_cr0;
        }

Cheers,
Rusty.