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Re: [Xen-devel] [PATCH] PCI uart: fix boot hang, and second S3 resume inactive timer list corruption

On 08/26/2013 03:52 PM, Jan Beulich wrote:
On 26.08.13 at 15:25, Tomasz Wroblewski<tomasz.wroblewski@xxxxxxxxxx>  wrote:
Nevertheless, the approach of your patch in simply giving up
the device (even if only termporarily) looks questionable to me
We'd rather need to restore full access to it I would think. But
yes, this hypervisor and Dom0 playing with the same device is
sort of a gray area.
Restore ioport access at the start of poll routine (if not on) and
disable it again at the end (if was not on)? I might do that (if you
really prefer), but intuitively that seems more likely to produce side
effects in dom0 kernel than skipping a poll in xen
As long as it's guaranteed to only be a poll (or a few of them) being
affected, this is fine. But what if an interrupt is being used?
I'm probably missing something so can you elaborate on this? Probably not what you are asking, but ns16550_interrupt function currently doesn't hang when ioports are disabled as a byproduct of the "while ( !(ns_read_reg(uart, IIR) & IIR_NOINT) )" test in there, which already causes it to break out on 0xFF regs


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