On 29/11/17 15:03, Boris Ostrovsky wrote: > On 11/29/2017 03:50 AM, Roger Pau Monné wrote: >> On Wed, Nov 29, 2017 at 09:21:59AM +0100, Juergen Gross wrote: >>> On 28/11/17 20:34, Maran Wilson wrote: >>>> For certain applications it is desirable to rapidly boot a KVM virtual >>>> machine. In cases where legacy hardware and software support within the >>>> guest is not needed, Qemu should be able to boot directly into the >>>> uncompressed Linux kernel binary without the need to run firmware. >>>> >>>> There already exists an ABI to allow this for Xen PVH guests and the ABI is >>>> supported by Linux and FreeBSD: >>>> >>>> https://xenbits.xen.org/docs/unstable/misc/hvmlite.html >> I would also add a link to: >> >> http://xenbits.xen.org/docs/unstable/hypercall/x86_64/include,public,arch-x86,hvm,start_info.h.html#Struct_hvm_start_info >> >>>> This PoC patch enables Qemu to use that same entry point for booting KVM >>>> guests. >>>> >>>> Even though the code is still PoC quality, I'm sending this as an RFC now >>>> since there are a number of different ways the specific implementation >>>> details can be handled. I chose a shared code path for Xen and KVM guests >>>> but could just as easily create a separate code path that is advertised by >>>> a different ELF note for KVM. There also seems to be some flexibility in >>>> how the e820 table data is passed and how (or if) it should be identified >>>> as e820 data. As a starting point, I've chosen the options that seem to >>>> result in the smallest patch with minimal to no changes required of the >>>> x86/HVM direct boot ABI. >>> I like the idea. >>> >>> I'd rather split up the different hypervisor types early and use a >>> common set of service functions instead of special casing xen_guest >>> everywhere. This would make it much easier to support the KVM PVH >>> boot without the need to configure the kernel with CONFIG_XEN. >>> >>> Another option would be to use the same boot path as with grub: set >>> the boot params in zeropage and start at startup_32. >> I think I prefer this approach since AFAICT it should allow for >> greater code share with the common boot path. > > zeropage is x86/Linux-specific so we'd need some sort of firmware (like > grub) between a hypervisor and Linux to convert hvm_start_info to > bootparams. qemu? Juergen
