FS#31944 - [linux] Xen PV guest support for i686 kernel

Attached to Project: Arch Linux
Opened by Steven Noonan (neunon) - Sunday, 14 October 2012, 07:24 GMT
Last edited by Tobias Powalowski (tpowa) - Monday, 15 October 2012, 06:32 GMT
Task Type Feature Request
Category Kernel
Status Closed
Assigned To Tobias Powalowski (tpowa)
Thomas Bächler (brain0)
Architecture i686
Severity Low
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Votes 0
Private No

Details

I am building unofficial Arch Linux AMI releases for Amazon EC2. This is the project page: http://www.uplinklabs.net/projects/arch-linux-on-ec2/

I currently don't have any 32-bit AMIs built because the kernel provided in i686-core does not have Xen paravirtual drivers enabled in the kernel config. I'm trying to avoid making packages which are specific to EC2, however, as I want end users to have a minimally modified installation. In particular I want to avoid forking the Arch Linux kernel package.

One option is to just enable the appropriate options in the mainline Arch i686 kernel, but the change looks a bit more invasive than I'd like. CONFIG_XEN depends on CONFIG_X86_PAE. Attached is the diff after doing 'make menuconfig' and enabling PAE, Xen, and the appropriate kernel modules (BLKDEV_FRONTEND, NETDEV_FRONTEND, etc). Most notably, this breaks OLPC support (which depends on !X86_PAE) and Open Firmware support.
   i686-xen.patch (9.9 KiB)
This task depends upon

Closed by  Tobias Powalowski (tpowa)
Monday, 15 October 2012, 06:32 GMT
Reason for closing:  Won't implement
Comment by Steven Noonan (neunon) - Sunday, 14 October 2012, 09:09 GMT
Better diff attached. I didn't notice some Xen modules were left out (XEN_WDT, XEN_NETDEV_BACKEND), some were not being built as modules (most of the frontend drivers), etc.
   i686-xen.patch (9.6 KiB)
Comment by Ionut Biru (wonder) - Monday, 15 October 2012, 04:53 GMT
is there a reason you don't want to use x86_64 kernel?
Comment by Steven Noonan (neunon) - Monday, 15 October 2012, 04:57 GMT
I already have x86_64 AMIs built out. If you're suggesting x86_64 kernel with i686 userspace, that won't work because 32-bit AMIs need to be entirely 32-bit due to what hardware they can land on.
Comment by Ionut Biru (wonder) - Monday, 15 October 2012, 05:04 GMT
but enabling PV in i686 requires PAE and we won't add this to our kernel.
Comment by Steven Noonan (neunon) - Monday, 15 October 2012, 05:04 GMT
That's what I was asking. If it's not acceptable that's fine, I can just build my own kernel. I'm just trying to avoid it. :)

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