On Mon, Jun 03, 2019 at 03:07:06PM +0100, Will Deacon wrote: > On Mon, Jun 03, 2019 at 12:23:03PM +0100, Dave Martin wrote: > > On Fri, May 31, 2019 at 06:04:16PM +0100, Andre Przywara wrote: > > > On Thu, 30 May 2019 16:13:10 +0100 > > > Dave Martin <Dave.Martin@xxxxxxx> wrote: > > > > > > > From: Amit Daniel Kachhap <amit.kachhap@xxxxxxx> > > > > > > > > This patch adds a runtime capabality for KVM tool to enable Arm64 8.3 > > > > Pointer Authentication in guest kernel. Two vcpu features > > > > KVM_ARM_VCPU_PTRAUTH_[ADDRESS/GENERIC] are supplied together to enable > > > > Pointer Authentication in KVM guest after checking the capability. > > > > > > > > Command line options --enable-ptrauth and --disable-ptrauth are added > > > > to use this feature. However, if those options are not provided then > > > > also this feature is enabled if host supports this capability. > > > > > > I don't really get the purpose of two options, I think that's quite > > > confusing. Should the first one either be dropped at all or called > > > something with "force"? > > > > > > I guess the idea is to fail if pointer auth isn't available, but the > > > option is supplied? > > > > > > Or maybe have one option with parameters? > > > --ptrauth[,=enable,=disable] > > > > So, I was following two principles here, either or both of which may be > > bogus: > > > > 1) There should be a way to determine whether KVM turns a given feature > > on or off (instead of magically defaulting to something). > > > > 2) To a first approaximation, kvmtool should allow each major KVM ABI > > feature to be exercised. > > > > 3) By default, kvmtool should offer the maximum feature set possible to > > the guest. > > > > > > (3) is well established, but (1) and (2) may be open to question? > > > > If we hold to both principles, it makes sense to have options > > functionally equivalent to what I suggested (where KVM provides the > > control in the first place), but there may be more convenient ways > > to respell the options. > > > > If we really can't decide, maybe it's better to drop the options > > altogether until we have a real use case. > > > > I've found the options very useful for testing and debugging on the SVE > > side, but I can't comment on ptrauth. Maybe someone else has a view? > > I'd prefer to drop them, to be honest. Whilst they may have been useful > during SVE development, it's not clear to me that they will continue to > be as useful now that things should be settling down. It's probably useful > to print out any features that we've explicitly enabled (or failed to > enable), but I'd stop there for the time being. I don't have a strong view on this. I'm happy to respin dropping the command line options and defaulting everthing to on: for hacking purposes, it's easy to keep a local branch. Cheers ---Dave _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
