From mboxrd@z Thu Jan 1 00:00:00 1970 From: Olaf Hering Subject: Re: audit_p2m errors, p2m_mmio_direct turns into p2m_ram_logdirty Date: Wed, 3 Nov 2010 14:59:22 +0100 Message-ID: <20101103135922.GA9273@aepfle.de> References: <20101102165429.GA30730@aepfle.de> <20101103121222.GF11016@whitby.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Return-path: Content-Disposition: inline In-Reply-To: <20101103121222.GF11016@whitby.uk.xensource.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: Tim Deegan Cc: "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org On Wed, Nov 03, Tim Deegan wrote: > > Today I tried it again in the hope to get some help for xenpaging > > debugging in xen-4.0, but it ran into a BUG right away. > > For some reason the p2m type set by set_mmio_p2m_entry for gfn 0xfee00 > > is 2 instead of 5 when audit_p2m checks it. > > I wans't able to reproduce this on xen-unstable tip. Were you using the > paging code at the time? Its with the 4.0 tree, and xenpaging starts much later. Its the early domain setup code. > > (XEN) p2m: audit_p2m(1839): OK: mfn=0x133b86, gfn=0xed47f, p2mfn=0xffffffffffffffff, lp2mfn=0x0 > > (XEN) p2m: audit_p2m(1941): mismatch: gfn 0xfee00 -> mfn 0x134012 -> gfn 0xffffffffffffffff (p2mt 2) > > That's a bug, though. > > Your line numbers don't match my tree, but I take it this is the third > (i.e. non-superpage) instance of this check? In that case it looks like > it's found a real bug - for any log-dirty RAM p2m entry the m2p ought to > match the p2m. Also an MMIO entry shouldn't become without becoming > normal RAM in the meantime. > > The next step, I'm afraid, is to trace where the type is getting > changed. If the pfn is the same on each run (and it look like it should > be) then you should be able to put an appropriate WARN_ON in > paging_write_p2m_entry() to catch all changes to that pfn's type. Thanks for looking into this. I will try to trace this and see where the type changes. Olaf