[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] HVMlite gains
On 15/03/2016 21:14, Luis R. Rodriguez wrote: > While discussing HVMLite with a few people a few questions have come > up. Since I only really understand a few possible gains with the > current design I wanted to get clarificaiton on a few which I simply > have no clue if we stand to gain from them, or if its on the roadmap: > > a) Will context switches use the actual CR3 register? Yes. HVMLite will use fully the full array of hardware virtualisation extensions, so gets its own pagetables and cr3. > b) Will IOPL live in the actual FLAGS register? Yes > c) Will guest-usable CPU features should show up in CPUID, and will > features that shouldn't be used should *not* show up in CPUID. For > instance currently you happen to boot Xen 4.4.0 with a new Linux dom0 > on a CPU that supports MPX what will happen? What about with HVMlite? I am desperately trying to fix the existing broken-ness. PV is too far beyond repair when it comes to the OSXSAVE bit, but the rest is fine. See my "x86: Improvements to cpuid handling for guests" series, v3 of which was posted today. With that series in place, a guest should always see correct features (give or take some "fun" with masking, but at least the xen_cpuid() path will still be correct). > d) Will acking an interrupt use the standard APIC mechanism? Do > any of the current Xen variants do that? Emulated APIC will be enabled by default. The "PV event" path will be available as an alternative. If a user desperately wishes to avoid the emulated APIC, they have the option to disable it in the domain config. > e) Can timing use RDTSC? I don't understand this question in the context of the others. RDTSC has (as far as I can tell) always been advertised and available for guest use. RDTSCP is a different matter, and I have half-fixed that brokenness; it should now work correctly in HVM guests. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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