Re: [Xen-devel] [PATCH v3 6/7] xen/x86: use flag byte for decision whether xen_cr3 is valid

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.03.18 at 13:51, <jgross@xxxxxxxx> wrote:
> Today cpu_info->xen_cr3 is either 0 to indicate %cr3 doesn't need to
> be switched on entry to Xen, or negative for keeping the value while
> indicating not to restore %cr3, or positive in case %cr3 is to be
> restored.
> 
> Switch to use a flag byte instead of a negative xen_cr3 value in order
> to allow %cr3 values with the high bit set in case we want to keep TLB
> entries when using the PCID feature.
> 
> This reduces the number of branches in interrupt handling and results
> in better performance (e.g. parallel make of the Xen hypervisor on my
> system was using about 3% less system time).
> 
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel