From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH] xen: find a better location for the real-mode trampoline Date: Tue, 18 Dec 2012 14:22:12 +0100 Message-ID: <50D06E04.7030904@redhat.com> References: <1354210461-9739-1-git-send-email-pbonzini@redhat.com> <50B87D6E02000078000ACBF2@nat28.tlf.novell.com> <50D078B702000078000B101F@nat28.tlf.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <50D078B702000078000B101F@nat28.tlf.novell.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: Jan Beulich Cc: xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org Il 18/12/2012 14:07, Jan Beulich ha scritto: >>>> On 30.11.12 at 09:33, "Jan Beulich" wrote: >>>>> On 29.11.12 at 18:34, Paolo Bonzini wrote: >>> On some machines, the location at 0x40e does not point to the beginning >>> of the EBDA. Rather, it points to the beginning of the BIOS-reserved >>> area of the EBDA, while the option ROMs place their data below that >>> segment. >>> >>> For this reason, 0x413 is actually a better source than 0x40e to get >>> the location of the real-mode trampoline. But it is even better to >>> fetch the information from the multiboot structure, where the boot >>> loader has placed the data for us already. >> >> I think if anything we really should make this a minimum calculation >> of all three (sanity checked) values, rather than throwing the other >> sources out. It's just not certain enough that we can trust all >> multiboot implementations. > > I never saw a response from you on this one - were you > intending to follow up, or did you (silently) expect us to sort > this out? No, just busy. I agree that checking all three is best. However, there is at least one known case where 0x40e doesn't work, so 0x413 and multiboot should be enough. Paolo