Re: [Xen-devel] [PATCH V3] tools/libxc, xen/x86: Added xc_set_mem_access_multi()

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Sep 06, 2016 at 01:27:21PM +0300, Razvan Cojocaru wrote:
> On 09/06/2016 01:16 PM, Ian Jackson wrote:
> > Razvan Cojocaru writes ("[PATCH V3] tools/libxc, xen/x86: Added 
> > xc_set_mem_access_multi()"):
> >> Currently it is only possible to set mem_access restrictions only for
> >> a contiguous range of GFNs (or, as a particular case, for a single GFN).
> >> This patch introduces a new libxc function taking an array of GFNs.
> >> The alternative would be to set each page in turn, using a userspace-HV
> >> roundtrip for each call, and triggering a TLB flush per page set.
> >>
> >> Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
> >> Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> > 
> > I have no objection with my tools maintainer hat on.  But I have a
> > question for you and/or the hypervisor maintainers:
> > 
> > Could this aim be achieved with a multicall ?  (Can multicalls defer
> > the TLB flush?)
> 
> I assume your question is: could we do multiple xc_set_mem_access()
> calls and then call something like xc_tlb_flush() at the end of it,
> instead of a singke xc_set_mem_access_multi() call?
> 

FWIW: I think you misunderstood, multicall is a Xen hypercall to batch
multiple hypercalls into one.

But as Jan said in the other reply, there is no multicall for HVM
guests (yet) -- see hvm/hvm.c:hvm_hypercall_table.

Wei.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel