From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jan Beulich" Subject: Re: [PATCH RFC] p2m: p2m_mmio_direct set RW permissions Date: Mon, 26 Jan 2015 17:06:12 +0000 Message-ID: <54C682140200007800059934@mail.emea.novell.com> References: <29df2db1-7845-42ee-99e0-901ec8f2930a@default> <54C11A7C.6090602@citrix.com> <20150122173435.GA4366@elena.ufimtseva> <54C2357F0200007800058A67@mail.emea.novell.com> <20150126165559.GA15522@elena.ufimtseva> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150126165559.GA15522@elena.ufimtseva> Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Elena Ufimtseva Cc: kevin.tian@intel.com, andrew.cooper3@citrix.com, tim@xen.org, xen-devel@lists.xen.org, yang.z.zhang@intel.com, boris.ostrovsky@oracle.com List-Id: xen-devel@lists.xenproject.org >>> On 26.01.15 at 17:57, wrote: > On Fri, Jan 23, 2015 at 10:50:23AM +0000, Jan Beulich wrote: >> >>> On 22.01.15 at 18:34, wrote: >> > (XEN) 00000000d56f0000 - 00000000d5fff000 (reserved) >> >> So this is where one of the RMRRs sits in (and also where >> the faults occur according to the two numbers you sent >> earlier, which - as others have already said - is an indication >> of the reported RMRRs being incomplete), ... >> >> > (XEN) 00000000d5fff000 - 00000000d6000000 (usable) >> > (XEN) 00000000d7000000 - 00000000df200000 (reserved) >> >> ... and this is the exact range of the other one. But the usable >> entry between them is a sign of the firmware not doing the >> best job in assigning resources. >> >> I don't, btw, think that blindly mapping all the reserved regions >> into PVH Dom0's P2M would be (or is, if that's what's happening >> today) correct - these regions are named reserved for a >> reason. In the case here it's actually RAM, not MMIO, and >> Dom0 (as well as Xen) has no business accessing these (for others >> this may be different, e.g. the LAPIC and IO-APIC ones below, >> but Xen learns/knows of them by means different from looking >> at the memory map). > > I understand this this. At the same time I think pv dom0 does exactly > this blind mapping. I also tried to map these regions as read-only and > that worked. Can be this an option for these ram regions? No - they're reserved, so there shouldn't be _any_ access to them. The only possible workaround I see as acceptable would be the already proposed addition of a command line option allowing to specify additional RMRR-like regions. Jan