> What is the scenario that you would want toolstack to set such flag? > > Shouldn't hypervisor always set the flag when the guest is never > unpaused and always clear / ignore that flag if the guest is ever > unpaused? If that's all is needed, why does toolstack need to get > involved?
You are right. I will not expose the flag to toolstack. ----- Original Message ----- From: wei.l...@citrix.com To: dongli.zh...@oracle.com Cc: jbeul...@suse.com, wei.l...@citrix.com, konrad.w...@oracle.com, sstabell...@kernel.org, t...@xen.org, dario.faggi...@citrix.com, ian.jack...@eu.citrix.com, george.dun...@eu.citrix.com, david.vra...@citrix.com, xen-devel@lists.xen.org, andrew.coop...@citrix.com Sent: Friday, September 16, 2016 6:55:33 PM GMT +08:00 Beijing / Chongqing / Hong Kong / Urumqi Subject: Re: [PATCH v4 2/2] xen: move TLB-flush filtering out into populate_physmap during vm creation On Fri, Sep 16, 2016 at 03:47:23AM -0700, Dongli Zhang wrote: > > > + /* > > > + * MEMF_no_tlbflush can be set only during vm creation phase when > > > + * is_ever_unpaused is still false before this domain gets unpaused > > > for > > > + * the first time. > > > + */ > > > + if ( unlikely(!d->is_ever_unpaused) ) > > > + a->memflags |= MEMF_no_tlbflush; > > > > So you no longer mean to expose this to the caller? > > hmmm.... I would prefer to expose this to the toolstack if it is OK for > maintainers. > > I copy and paste Wei's comments below: > > ============================================== > > > Rule 1. It is toolstack's responsibility to set the "MEMF_no_tlbflush" bit > > in memflags. The toolstack developers should be careful that > > "MEMF_no_tlbflush" should never be used after vm creation is finished. > > > > Is it possible to have a safety catch for this in the hypervisor? In > general IMHO we should avoid providing an interface that is possible to > create a security problem. > > ============================================== > > Hi Wei, since it is possible to have a safety catch now in the hypervisor (the > bit is allowed only before VM creation is finished), is it OK for you to > expose > MEMF_no_tlbflush bit to toolstack? > What is the scenario that you would want toolstack to set such flag? Shouldn't hypervisor always set the flag when the guest is never unpaused and always clear / ignore that flag if the guest is ever unpaused? If that's all is needed, why does toolstack need to get involved? Do I miss something here? Wei. > Thank you very much! > > Dongli Zhang _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel