Re: [Xen-devel] [PATCH 2/2] x86: use invpcid to do global flushing

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.03.18 at 14:11, <jgross@xxxxxxxx> wrote:
> On 05/03/18 13:57, Andrew Cooper wrote:
>> When we start using PCID for user mappings, then we don't need them to
>> be global, at which point we can require/expect that the only global
>> mappings are hypervisor ones which we expect to remain correct across a
>> write to cr3.  However, if we do this, then we need to use a bit other
>> than PAGE_GLOBAL to signify guest user mappings.
>> 
>> I think this is doable, but I don't think it is going to be trivial to
>> get correct.
> 
> Why would we want to keep any global mappings at all? What are they good
> for? Today the only case I could find where they make sense at all is
> for 64-bit pv-guests to keep hypervisor mappings in the TLB when the
> guest is switching between user and kernel mode.

Hypervisor and guest user mappings, that is.

Jan


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