Re: Xen 4.18.5_20250521nb0 not ELF binary (Was: Re: EFI and Xen)

[Chuck Zmudzinski <frchuckz%gmail.com@localhost>]

On 5/24/2025 3:40 AM, Manuel Bouyer wrote:
> On Fri, May 23, 2025 at 10:06:05PM -0400, Chuck Zmudzinski wrote:
>> On 5/23/2025 5:18 PM, Chuck Zmudzinski wrote:
>> > On 5/23/2025 4:22 PM, Manuel Bouyer wrote:
>> >> On Fri, May 23, 2025 at 04:19:46PM -0400, Chuck Zmudzinski wrote:
>> >>> On 5/23/2025 4:15 PM, Manuel Bouyer wrote:
>> >>> > On Fri, May 23, 2025 at 04:13:01PM -0400, Chuck Zmudzinski wrote:
>> >>> >> [...]
>> >>> >> I needed to acquire a PCI serial card to get some useful messages because the motherboard does not have a built-in serial port.
>> >>> >> 
>> >>> >> It appears Xen 4.18.4_20241221nb0 from pkgsrc crashes on my box before the NetBSD dom0 starts:
>> >>> >> 
>> >>> >> -------- snip ------
>> >>> >> (XEN) Xen call trace:
>> >>> >> (XEN)    [<ffff82d040261a00>] R intel_iommu_enable_eim+0/0xe0
>> >>> >> (XEN)    [<ffff82d040268ac4>] S iommu_enable_x2apic+0x24/0x70
>> >>> >> (XEN)    [<ffff82d0403f579d>] S x2apic_bsp_setup+0x12d/0x220
>> >>> >> (XEN)    [<ffff82d0403ff0e4>] S __start_xen+0x1af4/0x2620
>> >>> >> (XEN)    [<ffff82d040204434>] S __high_start+0x94/0xa0
>> >>> >> (XEN) 
>> >>> >> (XEN) 
>> >>> >> (XEN) ****************************************
>> >>> >> (XEN) Panic on CPU 0:
>> >>> >> (XEN) CONTROL-FLOW PROTECTION FAULT: #CP[0003] endbranch
>> >>> >> (XEN) ****************************************
>> >>> >> (XEN) 
>> >>> >> (XEN) Reboot in five seconds...
>> >>> >> (XEN) Resetting with ACPI MEMORY or I/O RESET_REG.
>> >>> >> -------- end messages ------
>> >>> > 
>> >>> > Do you have a way to disable x2apic in the BIOS ?
>> >>> 
>> >>> I can check later this evening but I have an appointment now.
>> >>> 
>> >>> > 
>> >>> >> 
>> >>> >> Please note only the pkgsrc version of Xen crashes. I can boot Xen with no problems using Xen packaged by Fedora, AlmaLinux, etc. on this box.
>> >>> > 
>> >>> > Is it the same Xen version ?
>> >>> 
>> >>> More or less - I know Xen 4.18.4 worked, now Fedora is at Xen 4.19.
>> >> 
>> >> strange; maybe they had a patch.
>> >> Note that I just updated xen in pkgsrc to 4.18.5
>> >> 
>> > 
>> > Actually, I do remember that Xen 4.19.1 from Fedora did not work on my box but a patch that was added in 4.19.2 fixed it. I see the patch I needed on the Xen 4.19 branch was not added in Xen 4.18.4 but it is added in Xen 4.18.5, so maybe it will be fixed in Xen 4.18.5. I will try it when I can download Xen 4.18.5.
>> > 
>> > Thanks.
>> 
>> I rebuilt the latest Xen from pkgsrc but no help. Then I searched
>> Google for information about the error I am getting which has to
>> do with Control-flow Enforcement Technology (cet) and tried experimenting
>> with the Xen cet= options.
>> 
>> Now I am not getting the crash, but just when it is ready to build the
>> PV Dom0, it complains that it does not have an ELF binary.
>> 
>> Note the magic incantation to get past the crash is to add the option
>> cet=no-ibt to the Xen command line.
>> 
>> With this configuration, I get:
>> 
>> (XEN) Xen version 4.18.5_20250521nb0 (chuckz@) (gcc (nb3 20231008) 10.5.0) debug=n Fri May 23 18:59:50 EDT 2025
>> (XEN) Latest ChangeSet: 
>> (XEN) build-id: 86afac8b52e2d124001208bb6261d17088a2f26f
>> (XEN) Bootloader: NetBSD/x86 EFI Boot (x64), Revision 1.2 (Mon Dec 16 13:08:11 UTC 2024) (from NetBSD 10.1)
>> (XEN) Command line: dom0_mem=2G com2=9600,8n1,0x40c0,16,1:0.0 console=com2 cet=no-ibt pv-l1tf=false
>> ... snip many messages
>> (XEN)  First cpu on runqueue, activating
>> (XEN) Adding cpu 17 to runqueue 2
>> (XEN) Adding cpu 18 to runqueue 2
>> (XEN) Adding cpu 19 to runqueue 2
>> (XEN) mcheck_poll: Machine check polling timer started.
>> (XEN) NX (Execute Disable) protection active
>> (XEN) d0 has maximum 4160 PIRQs
>> (XEN) *** Building a PV Dom0 ***
>> (XEN) ELF: not an ELF binary
>> (XEN) 
>> (XEN) ****************************************
>> (XEN) Panic on CPU 0:
>> (XEN) Could not construct domain 0
>> (XEN) ****************************************
>> (XEN) 
>> (XEN) Reboot in five seconds...
>> (XEN) Resetting with ACPI MEMORY or I/O RESET_REG.
>> 
>> I tried uncompressing (with gunzip) the netbsd-XEN3_DOM0.gz file, and I
>> tried omitting the dom0_mem setting, but neither change helped.
> 
> This one I don't know; what boot loader command are you using ?
> 

menu=Boot normally with Xen:dev hd2d:;rndseed /var/db/entropy-file;load /netbsd-XEN3_DOM0 console=pc;multiboot /xen.gz dom0_mem=2G com2=9600,8n1,0x40c0,16,1:0.0 console=com2 cet=no-ibt pv-l1tf=false

I also see two messages like this during boot from Xen with the Xen cet=no-ibt setting:

(XEN) alt table ffff82d04045b9d8 -> ffff82d04046c4d4

and many messages like this:

(XEN) altcall iommu_enable_x2apic+0x1e/0x70 dest intel_iommu_enable_eim has no endbr64
(XEN) altcall iommu_update_ire_from_apic dest io_apic_write_remap_rte has no endbr64
...