Disabling ACPI in the HVM configs was the only way to get Windows to
run decent (read as you know it to) without drivers on older versions of
Xen. If ACPI was left enabled on Windows HVMs on those versions of Xen, a
lot of processor time would be wasted on something. This has been fixed in
newer versions of Xen (I had a thread in the fedora-xen list regarding this
issue, and it turns out alder versions of KVM had the same issue and newer
versions don't). I always leave ACPI enabled so that Windows will signal
the VM to power off (shutdown/destroy itself) after shutting down. People
could have ACPI disabled because they learned to create the machines that
way or because they migrated from older versions of xen, so the real
question is, do you care and/or does it matter? In the does it matter
field, if the drivers will still function fine when these interrupts don't
exist, then you could just make note of this. In the do you care field,
theoretically, these potential users could install the ACPI kernel on their
existing systems after changing it to enabled (I say theoretically because
they have to know how and changing kernels doesn't always work smoothly),
and the only legitimate reason I know of would be for performance on older
versions of Xen. I could be remembering wrong, or there could be other
legitimate reasons, but hopefully someone else will speak up in the case of
either of those situations.
An afterthought: I believe instructions for installing Windows on
older versions of xen may have suggested pressing a key (F5 or F7) during
the first portion of Windows setup (while being prompted to press F2 or F5)
in order to disable ACPI in Windows while leaving it enabled on the HVM, in
this case, the only step a user would have to take is switching kernels.
Another afterthought, the libvirt-created xml domains where
virt-install is used and Windows is selected may disable ACPI, possibly just
for the first boot, possibly permanently, I don't know, that would make a
lot of people fall into the ACPI disabled category that don't necessarily
know it and/or don't necessarily know how to fix it.
Dustin
-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of James Harper
Sent: Tuesday, July 22, 2008 06:38
To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] anyone using acpi=0 under windows?
Does anyone use acpi=0 under windows? Is there a legitimate reason why
you might need to?
I'm trying to sort out some problems with the gplpv drivers and one of
the solutions would require acpi=1 to get access to more interrupts
(irq# > 15)
James
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