Re: [PATCHv4 1/2] x86/ept: invalidate guest physical mappings on VMENTER

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 14/12/15 15:00, David Vrabel wrote:
> On 14/12/15 14:52, Andrew Cooper wrote:
>> On 14/12/15 14:39, David Vrabel wrote:
>>> diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
>>> index eef0372..6e0cf89 100644
>>> --- a/xen/arch/x86/mm/p2m-ept.c
>>> +++ b/xen/arch/x86/mm/p2m-ept.c
> [...]
>>> +    on_selected_cpus(d->domain_dirty_cpumask,
>>>                       __ept_sync_domain, p2m, 1);
>> You can drop __ept_sync_domain() entirely by using
>> smp_send_event_check_mask() instead, which is a no-op IPI (and slightly
>> less overhead while holding the IPI lock).
> We need to wait until the IPI has been handled on the remote PCPUs since
> we may immediately free a page table page.  If a VCPU was still running
> it may use paging-structure-cache entries referring to that freed page.

Ah yes.  Better not do that.

As some future cleanup it would be nice to be able to do this without
specifying a function, but that is a minor detail and not relevant to
this patch.

~Andrew