On Tue, Apr 21, 2020 at 12:35:21PM +0200, Paolo Bonzini wrote: > Mostly looks good except for kernel parameters: [Just noticed this; somehow the KVM e-mails, which I explicitly Cced myself, aren't arriving in my Inbox.] > On 20/04/20 13:17, Kashyap Chamarthy wrote: > > +Enabling "nested" (x86) > > +----------------------- > > + > > +From Linux kernel v4.19 onwards, the ``nested`` KVM parameter is enabled > > +by default for Intel x86, but *not* for AMD. (Though your Linux > > +distribution might override this default.) > > It is enabled for AMD as well. Ah, thanks. Will correct. > > + > > +If your hardware is sufficiently advanced (Intel Haswell processor or > > +above which has newer hardware virt extensions), you might want to > > +enable additional features: "Shadow VMCS (Virtual Machine Control > > +Structure)", APIC Virtualization on your bare metal host (L0). > > +Parameters for Intel hosts:: > > + > > + $ cat /sys/module/kvm_intel/parameters/enable_shadow_vmcs > > + Y > > + > > + $ cat /sys/module/kvm_intel/parameters/enable_apicv > > + N > > + > > + $ cat /sys/module/kvm_intel/parameters/ept > > + Y > > > These are enabled by default if you have them, on all kernel versions. > So you may instead tell people to check them (especially > enable_shadow_vmcs and ept) if their L2 guests run slower. Noted, will amend. > > > > +Starting a nested guest (x86) > > +----------------------------- > > + > > +Once your bare metal host (L0) is configured for nesting, you should be > > +able to start an L1 guest with:: > > + > > + $ qemu-kvm -cpu host [...] > > + > > +The above will pass through the host CPU's capabilities as-is to the > > +gues); or for better live migration compatibility, use a named CPU > > +model supported by QEMU. e.g.:: > > + > > + $ qemu-kvm -cpu Haswell-noTSX-IBRS,vmx=on > > + > > +then the guest hypervisor will subsequently be capable of running a > > +nested guest with accelerated KVM. > > + > > The latter is only on QEMU 4.2 and newer. Also, you should group by > architecture and use third-level headings within an architecture. Okay, will adjust the structure. Thanks for the review. -- /kashyap
