From: Rusty Russell <rusty@rustcorp.com.au>
Date: Fri, 13 Feb 2015 06:43:43 +0000 (+1030)
Subject: lguest: don't look in console features to find emerg_wr.
X-Git-Tag: fixes-v4.0-rc1~61^2~7
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=55c2d7884e9a97c2f2d46d5818f783bf3dcc5314;p=pandora-kernel.git

lguest: don't look in console features to find emerg_wr.

The 1.0 spec clearly states that you must set the ACKNOWLEDGE and
DRIVER status bits before accessing the feature bits.  This is a
problem for the early console code, which doesn't really want to
acknowledge the device (the spec specifically excepts writing to the
console's emerg_wr from the usual ordering constrains).

Instead, we check that the *size* of the device configuration is
sufficient to hold emerg_wr: at worst (if the device doesn't support
the VIRTIO_CONSOLE_F_EMERG_WRITE feature), it will ignore the
writes.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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