On 01/07/15 16:51, Boris Ostrovsky wrote: > On 07/01/2015 11:46 AM, Andrew Cooper wrote: >> On 01/07/15 15:46, Roger Pau Monne wrote: >>> Introduce a new DOMCTL flag that can be used to disable device >>> emulation >>> inside of Xen for HVM guests. The following emulated devices are >>> disabled >>> when the XEN_DOMCTL_CDF_noemu is used: hpet, pmtimer, rtc, ioapic, >>> lapic, >>> pic and pmu. Also all the MMIO handlers are disabled. >>> >>> Signed-off-by: Roger Pau Monné <[email protected]> >>> Cc: Jan Beulich <[email protected]> >>> Cc: Andrew Cooper <[email protected]> >>> Cc: Boris Ostrovsky <[email protected]> >>> Cc: Suravee Suthikulpanit <[email protected]> >>> Cc: Aravind Gopalakrishnan <[email protected]> >>> Cc: Jun Nakajima <[email protected]> >>> Cc: Eddie Dong <[email protected]> >>> Cc: Kevin Tian <[email protected]> >> I would be hesitant to have a blanket change like this. >> >> Consider APICV/AVIC. For performance reasons, we absolutely want HVM >> and PVH to make use of them, as they are substantially more efficient >> using hardware support than evening using plain evtchn hypercalls. >> >> However, the flipside is that we must provide an LAPIC emulation to >> cover the bits which hardware cannot virtualise. >> >> As a random idea, how about having a new hypercall or hvmparam which >> provides a bitmap of permitted emulators? This would allow far finer >> grain control over what is and isn't available to a domain. > > I think we also need to decide on which subsets of emulators we are > going to support, otherwise test matrix will become pretty big. For > example, initially we may want to allow all (for what we now call HVM) > or none (PVH).
Right, but that can currently be enforced with an "if ( arg != 0 && arg != ~0 ) return -EOPNOTSUPP;" in the hypercall handler for now. It still leaves us with the ability to add in LAPIC emulation in the future by changing the auditing. A blanket "no emulation" boolean is very much harder to relax in the future. ~Andrew _______________________________________________ Xen-devel mailing list [email protected] http://lists.xen.org/xen-devel
