From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: fixed location of share info page in HVM guests Date: Tue, 28 Aug 2012 12:40:41 +0100 Message-ID: References: <20120828082302.GA27309@aepfle.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120828082302.GA27309@aepfle.de> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Olaf Hering Cc: xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 28/08/2012 09:23, "Olaf Hering" wrote: > On Tue, Aug 28, Keir Fraser wrote: > >> How about we guarantee that guests can use the 1MB in address range >> 0xFED00000-0xFEDFFFFF for whatever mappings they like, guaranteed unused (or >> at least, mapped with nothing useful) when guest kernel starts? >> >> This is already, and has always been, the case. But we can etch it in stone >> quite easily. :) > > 0xFED00000UL is appearently the hpet base adress. But if there is room > after that, then lets use that. However, I'm not familiar with these > things. Should the area appear in the E820 map as reserverd? If so, > where is the code which configures the guests E820 map? Okay, that was a bit too clever, trying to hide between IOAPIC and LAPIC pages. How about a bit lower in memory -- FE700000-FE7FFFFF? Everything in range FC000000-FFFFFFFF should already be marked E820_RESERVED. You can test that, and also see tools/firmware/hvmloader/e820.c:build_e820_table() (and note that RESERVED_MEMBASE == FC000000). Can document in hvmloader/config.h and have mem_alloc() test against it rather than hvm_info->reserved_mem_pgstart. -- Keir > Olaf