Re: [Xen-users] Is xen planning to support hvm guests booting under UEFI?

[jim burns <jim_burn@xxxxxxxxxxxxx>]

On Sat September 24 2011, 6:43:42 PM, Todd Deshane wrote:
> On Sat, Sep 24, 2011 at 5:34 PM, jim burns <jim_burn@xxxxxxxxxxxxx> wrote:
> > On Wed September 21 2011, 9:06:38 PM, jim burns wrote:
> >> Pls cc: me as I am not subscribed.
> > 
> > [...]
> > http://wiki.xensource.com/xenwiki/XenParavirtOps has been reworked
> > recently. Not sure if this was there before:
> > 
> > "Add EFI support in Linux pv-ops. Jan Beulich wrote patches to make Xen
> > hypervisor be able to compile as an EFI application. "Build xen.efi,
> > write up a config file for it to read (most importantly so it knows
> > what Dom0 kernel and initrd to use), and you should be good to go
> > (provided the EFI implementation isn't too flawed). This being an EFI
> > application you can simply run it from the shell prompt. Parameter for
> > Xen.efi is -cfg <file>, and <file> has: kernel=, ramdisk=, options=,
> > video=gfx-x. The Linux pv-ops needs at least to parse
> > XEN_VGATYPE_EFI_LFB data, E820 parsed (should be working) and give the
> > ACPI subsystem a pointer to the ACPI DSDT without consulting EBDA."
> > 
> > This doesn't solve the Windows 8 hvm problem, but at least EFI is being
> > considered.
> 
> There was a google summer of code project around UEFI:
> http://code.google.com/p/google-summer-of-code-2011-tianocore/downloads/deta
> il?name=Bei_Guan.tar.gz&can=2&q=
> 
> I don't know if it was submitted to xen-devel, but you can follow up
> with the xen-devel mailing list if you are interested.
> 
> Hope that helps.

The article I quoted was from http://www.itworld.com/it-
managementstrategy/205255/windows-8-oem-specs-
may-block-linux-booting :

"Red Hat's Matthew Garrett was one of the first to notice that according to 
the new logo rules, all Windows 8 machines will need to be have the Unified 
Extensible Firmware Interface (UEFI) instead of the venerable BIOS firmware 
layer. BIOS has been pretty much the sole firmware interface for PCs for a 
long time.

The EFI system has slowly been making headway in recent years, and right now 
EFI firmware is compatible with Windows supporting the GUID Partition Table 
(GPT), OS X/Intel, and Linux 2.6 and beyond machines. EFI is seen as a better 
hardware/software interface than BIOS, since it is platform-agnostic, runs in 
32- or 64-bit mode, and GPT machines can handle boot partitions of up to 9.4 
zettabytes. (That's 9.5 billion terabytes to you and me.)

EFI, and the later UEFI specification, is not the problem for Linux. The 
problem is Microsoft's other requirement for any Windows 8-certified client: 
the system must support secure booting. This hardened boot means that "all 
firmware and software in the boot process must be signed by a trusted 
Certificate Authority (CA)," according to slides from a recent presentation on 
the UEFI boot process made by Arie van der Hoeven, Microsoft Principal Lead 
Program Manager."

Putting aside the signing problem for now, the immediate problem is qemu-dm as 
the emulator for hvm guests, since it provides an emulated *bios*. Or 
hvmloader as the bootloader. The url Todd provides points to a project to 
modify 'ovmf', an EFI bootloader, to be xen hvm aware. Windows 8 will be a 
game changer, if the article is right. Hope plans are being made to 
incorporate some sort of EFI bootloader into xen.

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