Pkg xen devel - Jan 2024 - Bug#988477: Also observing #988477

Package: src:xen
Version: 4.14.1+11-gb0b734a8b3-1
Severity: critical
Justification: causes serious data loss
X-Debbugs-Cc: debianbts at virtualzone.hu

Dear Maintainer,

after a clean install of bullseye/testing the xen dmesg shows the following
message:
(XEN) AMD-Vi: IO_PAGE_FAULT: 0000:01:00.1 d0 addr fffffffdf8000000 flags 0x8 I
this is the sata device:
01:00.1 SATA controller: Advanced Micro Devices, Inc. [AMD] 400 Series Chipset
SATA Controller (rev 01)
or on another mb
01:00.1 SATA controller: Advanced Micro Devices, Inc. [AMD] Device 43eb
in the case of write operations - ie. dbench or windows guest - there are a lot
of messages
sometimes the filesystem goes to read-only state, and the windows guest goes
bsod
tested on 3 hw:
1. asus prime b450m-a, ryzen 5 2600x, md raid1, 2x samsung 1TB 860evo, lvm:
problem does appear
2. asus prime b550m-k, ryzen 5 5600x, md raid1, 2x samsung 1TB 870evo, lvm:
problem does appear
3. asus prime b550m-k, ryzen 5 5600x, 1x samsung 1TB 850evo, lvm: problem does
not appear
3. asus prime b550m-k, ryzen 5 5600x, 1x samsung 128GB 840pro, lvm: problem does
not appear
3. asus prime b550m-k, ryzen 5 5600x, samsung 1TB 850evo + samsung 128GB 840pro,
lvm, dbench on 2 ssds in parallel: problem does appear

as i see, the problem does appear, when writes data parallel to 2 ssds

Thanks!

-- System Information:
Debian Release: bullseye/sid
  APT prefers testing-security
  APT policy: (500, 'testing-security'), (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 5.10.0-6-amd64 (SMP w/12 CPU threads)
Locale: LANG=hu_HU.UTF-8, LC_CTYPE=hu_HU.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

xen-hypervisor-4.14-amd64 depends on no packages.

Versions of packages xen-hypervisor-4.14-amd64 recommends:
ii  xen-hypervisor-common  4.14.1+11-gb0b734a8b3-1
ii  xen-utils-4.14         4.14.1+11-gb0b734a8b3-1

xen-hypervisor-4.14-amd64 suggests no packages.

-- no debconf information

i tested on 4th hw

4. asus m4n78 pro, phenom ii x4 905e, md raid1, 2x samsung 1TB 860evo, 
lvm: problem does not appear

as i see, not all mb/chipset/sata pcie device affected

Thanks!

severity 988477 normal
tags 988477 + moreinfo + upstream - bullseye-ignore
thanks

Hi!

On 6/13/21 3:58 PM, Imre Sz?ll?si wrote:
> i tested on 4th hw
> 
> 4. asus m4n78 pro, phenom ii x4 905e, md raid1, 2x samsung 1TB 860evo, 
> lvm: problem does not appear
> 
> as i see, not all mb/chipset/sata pcie device affected
Thanks for your report, and for trying out different combinations of
hardware.

While doing a short internet search about the problems you're seeing
while using AMD ryzen, sata, nvme and iommu, I suspect this problem does
not have a lot to do with Xen specifically, but more with the hardware
and its firmware.

This also means that it's not a Debian packaging problem, and it cannot
be fixed by me (or the Debian Xen team). If you want to research this
problem more, I can maybe be of some help by providing suggestions.
Still, you will have to do all of the actual work, since I do not have
your hardware here.

The first thing I would suggest is to try reproduce the problem when
booting with just Linux without Xen, and then trying the dbench test.

If you don't actually need to directly pass-through hardware to a Xen
guest, you can also try disabling iommu, or researching other iommuoptions that
can serve as a workaround.

In any case, further reports will need to have more detailed
information. For example, instead of "there are a lot of messages",
provide a text attachment with a piece of logging that shows these messages.

I'm tagging this bug 'moreinfo' now, since it will depend on your
availability and abilities to work on it to have it advance.

Have fun,
Hans van Kranenburg

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tags 988477 - moreinfo
found 988477 4.17.2+76-ge1f9cb16e2-1~deb12u1
affects 988477 src:linux
severity 988477 critical
quit

I am also observing #988477 occur.  This machine has a AMD Zen 4
processor.  The first observation was when motherboard/processor was
swapped out, the older motherboard/processor was several generations old.

The pattern which is emerging is Linux MD RAID1 plus recent AMD processor
which has full IOMMU functionality.  The older machine was believed to
have an IOMMU, but the BIOS wasn't creating appropriate ACPI tables
(IVRS) and thus Xen was unable to utilize it.

This seems to be occuring with a small percentage of write operations.
Subsequent read operations appear to be fine.

I am not convinced this is a Xen bug.  I suspect this is instead a bug
in the Linux MD subsystem.  In particular if the DMA interface was
designed assuming only a single device would ever access any page, but
the MD RAID1 driver is reusing the same page for both devices.

IOMMU page release could be handled by marking the page unused in a
device data structure and later removed by sweeping a table.  In such
case if the MD-RAID1 driver was to redirect the page to another device
between these two steps, the entry for a subsequent device could be wiped
out when trying to invalidate an entry for a prior device.


Anyway, I'm also observing bug #988477.  This could also be a kernel bug.
So far no crashes/confirmed data loss have occured, but sweeping the
mirror does turn up small numbers of inconsistencies.


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