From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brent Casavant Date: Tue, 24 Jan 2006 06:30:42 +0000 Subject: Re: [PATCH] SN2 user-MMIO CPU migration Message-Id: <20060124001932.Q80998@chenjesu.americas.sgi.com> List-Id: References: <20060118163305.Y42462@chenjesu.americas.sgi.com> In-Reply-To: <20060118163305.Y42462@chenjesu.americas.sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org On Mon, 23 Jan 2006, Grant Grundler wrote: > Would an app first need to mmap an uncached address? > Or some other obvious "marker" that might warn the kernel? I'm not sure an uncached address would be appropriate, as I believe there are other non-IO uncached mappings which can be performed (whatever the fetchop stuff morphed into, for example -- I can't remember what its called now). The only obvious marker I can thing of would be a flag in the mm struct set by a device driver when such a mapping occurs. All relevant device drivers would need to be updated, and we'd need to handle partial unmappings, shared mappings and the like. > I'm wondering if one could check some easily reachable state > (or flag) before calling platform_switch_from() and thus > mitigate Tony's concern. I can't think of any obviously correct state/flag to inspect, short of the other suggestion I made tonight. Brent -- Brent Casavant All music is folk music. I ain't bcasavan@sgi.com never heard a horse sing a song. Silicon Graphics, Inc. -- Louis Armstrong