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Re: [Xen-devel] [PATCH RFC] xen/console: buffer and show origin of guest PV writes

On 08/13/2013 12:40 PM, Pasi Kärkkäinen wrote:
On Tue, Aug 13, 2013 at 12:34:19PM -0400, Daniel De Graaf wrote:
Guests other than domain 0 using the console output have previously been
controlled by the VERBOSE define, but with no designation of which
guest's output was on the console. This patch converts the HVM output
buffering to be used by all domains, line buffering their output and
prefixing it with the domain ID. This is especially useful for debugging
stub domains during early boot.

Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>


A few questions for discussion (the reason this is an RFC):

1. HVM guests' output is currently limited to printable characters; do
we want to implement the same restriction on PV guests?

2. The prefix on the serial console for PV output is "(XEN) d5: ", while
HVM output is still "(XEN) HVM5: "; should these be made consistent?

3. Should we change to allowing console output by default, since it is
now controlled by log levels?

Also having timestamps before the log entries would be nice (like Linux has)..

-- Pasi

Since this uses printk, if timestamps are turned on with opt_console_timestamps,
they will beadded to the output. It looks like the timestamp only has 1 second
resolution, unlike Linux - it might be useful to update that.

Daniel De Graaf
National Security Agency

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