From mboxrd@z Thu Jan 1 00:00:00 1970 From: Olaf Hering Subject: Re: [PATCH 18/21] xenpaging: prevent page-out of first 16MB Date: Fri, 17 Dec 2010 13:18:24 +0100 Message-ID: <20101217121824.GA1336@aepfle.de> References: <20101126134901.384130351@aepfle.de> <20101126134907.311234491@aepfle.de> <20101216165942.GA17353@aepfle.de> <4D0B3B550200007800028A25@vpn.id2.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Return-path: Content-Disposition: inline In-Reply-To: <4D0B3B550200007800028A25@vpn.id2.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Jan Beulich Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On Fri, Dec 17, Jan Beulich wrote: > >>> On 16.12.10 at 17:59, Olaf Hering wrote: > > On Fri, Nov 26, Olaf Hering wrote: > > > >> This is more a workaround than a bugfix: > >> Don't page out first 16MB of memory. > >> When the BIOS does its initialization process and xenpaging removes pages, > >> crashes will occour due to lack of support of xenpaging. > > > > While looking at this again, I came up with this change. Any idea whats > > at 512K during BIOS startup? > > > > > > Subject: xenpaging: prevent page-out of gfn 0x80 > > > > Add a workaround for missing handling of paged-out pages during BIOS > > startup. > > For some reason, only gfn 0x80 is affected. > > > > (XEN) HVM3: HVM Loader > > (XEN) traps.c:649:d3 Bad GMFN 80 (MFN ffffffffff) to MSR 40000000 > > This clearly is another place where page-in needs to be triggered. Yes, thats true. I had a printk in gfn_to_mfn for some months, and it did not trigger during my testing. But then, I also had the patch which keeps the first 16MB in memory. So as it stands, gfn_to_mfn() should call p2m_mem_paging_populate() at least, even if that does not fix this crash. I think the few gfn_to_mfn* variants should not return the paging types anymore, and just sleep until the page is back. Thats something for next year, as time runs out for me. And: I think the various redefines of those functions/macros can go as well. Olaf