On Thu, Apr 5, 2018 at 7:33 PM, Boris Ostrovsky <boris.ostrov...@oracle.com> wrote: > On 04/05/2018 01:11 PM, Juergen Gross wrote: >> On 05/04/18 16:56, George Dunlap wrote: >>> On Thu, Apr 5, 2018 at 3:09 PM, Juergen Gross <jgr...@suse.com> wrote: >>>> On 05/04/18 15:42, George Dunlap wrote: >>>>> On Thu, Apr 5, 2018 at 2:06 PM, Juergen Gross <jgr...@suse.com> 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. >>>> Sow you would hurt BSD which does read the RSDP address correctly but >>>> (today) has no such ELF note. > > > This can be predicated on > ELFNOTE(Xen, XEN_ELFNOTE_GUEST_OS, .asciz "linux") > > BSD will behave as it does now. For linux we could add feature flag (or > errata flag). Unfortunately I don't see a way to extract major.minor > from the headers, otherwise we could use that.
OTOH, one advantage of having a separate elfnote, rather than gating it on Linux version, is that if a distro wanted to, they could do their own backport to (say) Linux 4.15 and reap the advantages. -George _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
