From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Andres Lagar-Cavilla" Subject: Re: [PATCH 3 of 7] Use a reserved pfn in the guest address space to store mem event ringsg Date: Tue, 6 Mar 2012 11:27:34 -0800 Message-ID: <520db0ee1d39709857379ff13c60244a.squirrel@webmail.lagarcavilla.org> References: <0e79f8005b6b68e84a0f.1329977108@xdev.gridcentric.ca> <1330434093.31269.150.camel@zakaz.uk.xensource.com> <5e43716b77c694ad491d82077777b705.squirrel@webmail.lagarcavilla.org> <1330588073.10008.113.camel@dagon.hellion.org.uk> <20120301151733.GA48103@ocelot.phlegethon.org> <5386f6530efff6dfa885941add2f1efc.squirrel@webmail.lagarcavilla.org> <20120301173226.GA49888@ocelot.phlegethon.org> <443f6b507519c7eb7d8193684f3c5532.squirrel@webmail.lagarcavilla.org> <20120301175254.GB49888@ocelot.phlegethon.org> Reply-To: andres@lagarcavilla.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120301175254.GB49888@ocelot.phlegethon.org> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Tim Deegan Cc: "olaf@aepfle.de" , "xen-devel@lists.xensource.com" , Ian Campbell , "andres@gridcentric.ca" , Ian Jackson , "keir.xen@gmail.com" , "adin@gridcentric.ca" List-Id: xen-devel@lists.xenproject.org > At 09:44 -0800 on 01 Mar (1330595065), Andres Lagar-Cavilla wrote: >> > At 08:30 -0800 on 01 Mar (1330590637), Andres Lagar-Cavilla wrote: >> >> > At 07:47 +0000 on 01 Mar (1330588073), Ian Campbell wrote: >> >> >> > > Is there no scope for making these pages owned by the domain >> but >> >> not >> >> >> > > actually part of the P2M? We can cope with that for other >> types >> >> of >> >> >> magic >> >> >> > > page, can't we? >> >> > >> >> > It would need a new operation to map the ring into the tool that >> uses >> >> > it; normal map-foreign-page ops need a GFN. >> >> >> >> Actually, confirmed: we can call xc_domain_decrease_reservation on >> the >> >> ring after it's mapped by the helper. Guest won't get at it. Nothing >> >> breaks. >> > >> > But that would only work if: >> > - the helper always attaches before the guest gets to run; and >> >> The helper will ignore whatever contents there were on the page. And if >> the guest is out there poking in e820 reserved ranges, then the guest >> has >> it coming. Note that we've narrowed the window of "vulnerability". >> >> > - you never need to restart the helper. >> >> The helper can re-populate the pfn every time it starts. That's >> contemplated in the current patch series. In fact it can do it >> "atomically" by pausing the guest. > > OK, that seems good enough. Great, so I'll post this whole series again. I'll include the "remove ring from physmap" bits. And I'll add an Acked-by from Ian C for the tools bits. Cheers! Andres > > Tim. >