Re: Regression booting Linux kernel 5.16.1 under Xen: Failed to update kernel mapping for mfn=6930582 pfn=524288

[Juergen Gross <jgross@xxxxxxxx>]

On 18.01.22 11:53, Sander Eikelenboom wrote:
> L.S.,
>
> Both Linux kernel 5.16.0 and 5.16.1 fail to boot as Dom0 under 
> xen-unstable and crash early in boot on my hardware.
> With Linux 5.15.13 it boots fine. Serial log is below.
...

> (XEN) [0000001b1ffedeb8] Command line: dom0_mem=2048M,max:2048M 
> loglvl=all guest_loglvl=all console_timestamps=datems 
> vga=gfx-1280x1024x32 no-cpuidle com1=38400,8n1 console=vga,com1 
> ivrs_ioapic[6]=00:14.0 iommu=on,verbose,debug conring_size=128k 
> ucode=scan sched=credit2 gnttab_max_frames=64 reboot=a
...

> mapping kernel into physical memory
> about to get started...
> [    0.000000] Linux version 5.16.1-20220118-doflr-mac80211debug+ 
> (root@serveerstertje) (gcc (Debian 8.3.0-6) 8.3.0, GNU ld (GNU Binutils 
> for Debian) 2.31.1) #1 SMP PREEMPT Tue Jan 18 10:49:09 CET 2022
> [    0.000000] Command line: root=/dev/mapper/serveerstertje_ssd-root ro 
> verbose earlyprintk=xen mem=2048M console=hvc0 scsi_mod.use_blk_mq=1 
> console=tty0 acpi_enforce_resources=lax max_loop=30 loop_max_part=10 
> r8169.use_dac=1 loglevel=10 nomodeset net.ifnames=0 biosdevname=0 
> xen-pciback.hide=(00:14.2)(04:00.*)(08:00.0)(09:00.*)(0a:00.0)(0d:00.0)
...

> [    0.135670] ------------[ cut here ]------------
> [    0.135690] Failed to update kernel mapping for mfn=6930582 pfn=524288
> [    0.135701] WARNING: CPU: 0 PID: 0 at arch/x86/xen/setup.c:312 
> xen_remap_memory+0x191/0x26c
There seems to be a problem with rearranging the dom0 memory layout
to match that of the host. Especially it is going sideways when trying
to remap a memory frame to PFN 524288 (0x80000).

You are limiting dom0 memory to 2 GB via Xen command line, but in
addition to that you specify "mem=2048M" for the dom0 kernel, too. This
should cap memory from PFN 0x80000 onwards, hence the failure when dom0
tries to remap a frame into this area.

Can you please try removing the "mem=2048M" from the dom0 parameters?

I think there has been a kernel commit fixing the correct handling of
the "mem=" parameter in 5.16, which might be the reason why you are
seeing the crash only now.


Juergen

Attachment: OpenPGP_0xB0DE9DD628BF132F.asc
Description: OpenPGP public key

Attachment: OpenPGP_signature
Description: OpenPGP digital signature