From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [PATCH RFC 0/2] Linux: possible ixes for mapping high MMIO regions Date: Fri, 3 Jan 2014 13:35:13 -0500 Message-ID: <20140103183513.GC28915@phenom.dumpdata.com> References: <1388767522-11768-1-git-send-email-david.vrabel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1388767522-11768-1-git-send-email-david.vrabel@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: David Vrabel Cc: Boris Ostrovsky , xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On Fri, Jan 03, 2014 at 04:45:20PM +0000, David Vrabel wrote: > This a possible fix for the problems with mapping high MMIO regions in > certain cases (e.g., the RDMA drivers) as not all mappers were > specifing the _PAGE_IOMAP which meant no valid MFN could be found and > the resulting PTE would be marked as not present, causing subsequent > faults. > > It assumes that anything that isn't RAM (whether ballooned out or not) > is an I/O region and thus should be 1:1 in the p2m. Ballooned frames > are still marked as missing in the p2m as before. > > As a follow on, mfn_to_pfn() is (hopefully) extended to do the right > thing with such an MFN. This means the Xen-specific _PAGE_IOMAP PTE > flag can be removed, Woot! > > This series is posted as an early RFC in the hope that is an > acceptable approach. It has only seen the bare minimum of smoke > testing (my test dom0 didn't explode). In particular, I've not > actually tested it with a device with a high MMIO. I can do in a couple of weeks. > > David >