On Thu, Apr 5, 2018 at 2:06 PM, Juergen Gross <jgross@xxxxxxxx> wrote: > On 05/04/18 15:00, Boris Ostrovsky wrote: >> On 04/05/2018 08:19 AM, Juergen Gross wrote: >>> On 05/04/18 12:06, George Dunlap wrote: >>> >>>> Aren't there flags in the binary somewhere that could tell the >>>> toolstack / Xen whether the kernel in question needs the RSDP table in >>>> lowmem, or whether it can be put higher? >>> Not really. Analyzing the binary whether it accesses the rsdp_addr in >>> the start_info isn't the way to go, IMO. >>> >>> I've sent a patch to xen-devel adding a quirk flag to the domain's >>> config to enable the admin special casing such an "old" kernel. >> >> Can we backport latest struct hvm_start_info changes (which bumped >> interface version) to 4.11 and pass RSDP only for versions >=1? > > And this would help how? > > RSDP address is passed today, the kernel just doesn't read it. And > how should Xen know which interface version the kernel is supporting? > And Xen needs to know that in advance in order to place the RSDP in > low memory in case the kernel isn't reading the RSDP address from > start_info. But the kernel image has ELF notes, right? You can put one that indicates that this binary *does* know how to read the RSDP from the start_info, and if you don't find that, put it in lowmem. -George