Re: [Xen-users] xen domU segfaults with xpti on intel based systems

[Tomas Mozes <hydrapolic@xxxxxxxxx>]

On Fri, Jan 11, 2019 at 9:21 AM Juergen Gross <jgross@xxxxxxxx> wrote:

On 11/01/2019 07:05, Tomas Mozes wrote:
> Hello,
> we are observing random PV domU segfaults on Intel based systems with
> XPTI enabled. These segfaults were not present in Xen 4.9.2 and can be
> reproduced on 4.9.3/4.10.2/4.11.1. <http://4.11.1.> The problem can be
> mitigated by adding xpti=false to xen command line options.
>
> Some of the affected systems are Debian 8/9 (Debian 10 with kernel 4.18
> seems to work fine) and NetBSD 7. It's harder to reproduce the segfaults
> on Debian, but on NetBSD it's almost instant.

Hmm, as we haven't received any similar reports, I suspect there is
something special on your side.

Can you please be more specific regarding:

- hardware (machine type(s), processor model(s), ...)
- other config options (hypervisor command line, hypervisor .config)

A hypervisor log (output of "xl dmesg") would help, too. Please add
"loglvl=all guest_loglvl=all" to the hypervisor command line for that
purpose. If possible use a debug hypervisor for this test, as that
will produce more diagnostic output.


Juergen

These segfaults were actually spotted by the gmp project maintainer and only later they were locally reproduced on other machine (intel too).

A machine on which it can be reproduced: Intel DH87MC with Intel Core i7-4770 CPU @ 3.40GHz on Linux Gentoo (Haswell)
But for example i cannot reproduce on my desktop machine: Intel DH77EB with Intel Core i5-3570 CPU @ 3.40GHz (Ivy Bridge)

Grub options for the kernel/xen:
GRUB_CMDLINE_LINUX="panic=30 net.ifnames=0 domdadm"
GRUB_CMDLINE_XEN="dom0_mem=4G gnttab_max_frames=256 ucode=scan loglvl=all guest_loglvl=all console_to_ring console_timestamps=date conring_size=1m smt=true"

Attachment: xl-dmesg.txt
Description: Text document

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