On Tue, 2013-01-22 at 10:15 +0100, Mattias Eriksson wrote: > Hi! > > I have switched back to the current stable kernel in squeeze, 2.6.32-46, since I need the > machine to be up and running. And now it is just as stable as it was before. > > Even though I have never had any real issues using xen and VIA nano (64bit), the > CPU is officially not supported by xen, as far as I can see: > > (XEN) Domain heap initialised > (XEN) CPU: Vendor unknown, using generic init. > (XEN) CPU: Your system may be unstable. > (XEN) Processor #0 6:15 APIC version 20 > > So, I think there are to many "uncertainties" for me to dig into this further. [...] Yes, there may be quirks and bugs in VIA/Centaur processors that Xen should handle (which I couldn't find any documentation about). However: <http://bugs.debian.org/660425> is a report of an alignment check under Xen while running Linux 2.6.32, and Jonathan Nieder found (message #17) more reports of this - on Intel and AMD processors. In all these cases (and yours) the AC flag is shown as enabled, so alignment checks should be expected. The connection to Xen is this: the AC flag can be set by any program, but the processor ignores it when running code at the maximum privilege level. So normally the kernel is not affected, but under Xen it is running at lower privilege and therefore it is affected. Xen has to clear the AC flag whenever it switches from user mode to a (PV) guest kernel. I don't think the guest kernel itself needs to be aware of this because there is never a direct transition from user mode to kernel mode. Ben. -- Ben Hutchings Q. Which is the greater problem in the world today, ignorance or apathy? A. I don't know and I couldn't care less.
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