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xen-devel
Re: [Xen-devel] Serial console problem with Xen 3.0
On 7 Apr 2006, at 15:44, Don Zickus wrote:
Me too. Adding "sync_console" at least repaired the console *output*.
I
still have the problem that keyboard input does not reach linux, as it
seems. Here is my config:
Adding "pnpacpi=off" to the command line is our quick and dirty hack
for
now. Don't know the root cause yet, but at least it will get you
going.
I have some suspicion that this, and the IRQ flooding issues that suse
have been seeing, may be due to insufficient checking and translation
and book-keeping at the ioapic management interface that Xen exports.
See ioapic_guest_write() in xen/arch/x86/io_apic.c. Domain0 is
responsible for IRQ steering and routing, and therefore for most of the
management of IO-APICs, *but*:
1. Xen is responsible for masking/unmasking as part of normal
interrupt servicing.
2. Xen may own some of the interrupts routed via the IO-APIC (serial
and timer). Domain0 won't necessarily know about these and I think in
the case of serial interrupt in particular it may end up screwing that
IRQ line, in theory.
It may be worth getting Xen and XenLinux to dump verbose info about
their view of IO-APIC state, and maybe add tracing to
ioapic_guest_write() and see how domain0 is trying to drive the IO
APICs. You may well see some IO APIC write coming thru just before the
serial line goes dead. If so, the question will be whether the problem
is due to broken checking/translating in Xen, or whether a fix is
needed to dom0 ioapic code.
-- Keir
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