[v4,0/7] Poisoned memory recovery on reboot

Message

“William Roche Dec. 14, 2024, 1:45 p.m. UTC

From: William Roche <[e-mail]>

Hello David,

Here is an new version of our code and an updated description of the
patch set:

 ---
This set of patches fixes several problems with hardware memory errors
impacting hugetlbfs memory backed VMs and the generic memory recovery
on VM reset.
When using hugetlbfs large pages, any large page location being impacted
by an HW memory error results in poisoning the entire page, suddenly
making a large chunk of the VM memory unusable.

The main problem that currently exists in Qemu is the lack of backend
file repair before resetting the VM memory, resulting in the impacted
memory to be silently unusable even after a VM reboot.

In order to fix this issue, we take into account the page size of the
impacted memory block when dealing with the associated poisoned page
location.

Using the page size information we also try to regenerate the memory
calling ram_block_discard_range() on VM reset when running
qemu_ram_remap(). So that a poisoned memory backed by a hugetlbfs
file is regenerated with a hole punched in this file. A new page is
loaded when the location is first touched.

In case of a discard failure we fall back to remapping the memory
location. We also have to reset the memory settings and honor the
'prealloc' attribute.

This memory setting is performed by a new remap notification mechanism
calling host_memory_backend_ram_remapped() function when a region of
a memory block is remapped.

We also enrich the messages used to report a memory error relayed to
the VM, providing an identification of memory page and its size in
case of a large page impacted.
 ----
 
 About patch 3/7, I still think that generating an additional message
 in the kvm_hwpoison_page_add() function creates a cleaner code without
 the need to repeat it for x86 and ARM. The message would be displayed
 before all the injection messages issued because of the large page
 failure. But we could go with this version if you prefer the existing
 message to be enriched.
 
 About patch 7/7, I could merge it with your patch 6/7 if you agree.
 
 
v3 -> v4:
. Fixed some commit messages typos
. Enhanced some code comments
. Changed the discard fall back conditions to consider only anonymous
  memory
. Fixed missing some variable name changes in intermediary patches.
. Modify the error message given when an error is injected to report
  the case of a large page
. use snprintf() to generate this message
. Adding this same type of message in the ARM case too


This code is scripts/checkpatch.pl clean
'make check' runs fine on both x86 and Arm.


David Hildenbrand (3):
  numa: Introduce and use ram_block_notify_remap()
  hostmem: Factor out applying settings
  hostmem: Handle remapping of RAM

William Roche (4):
  hwpoison_page_list and qemu_ram_remap are based on pages
  system/physmem: poisoned memory discard on reboot
  accel/kvm: Report the loss of a large memory page
  system/physmem: Memory settings applied on remap notification

 accel/kvm/kvm-all.c       |   2 +-
 backends/hostmem.c        | 189 +++++++++++++++++++++++---------------
 hw/core/numa.c            |  11 +++
 include/exec/cpu-common.h |   3 +-
 include/exec/ramlist.h    |   3 +
 include/sysemu/hostmem.h  |   1 +
 system/physmem.c          |  88 +++++++++++++-----
 target/arm/kvm.c          |  13 +++
 target/i386/kvm/kvm.c     |  18 +++-
 9 files changed, 225 insertions(+), 103 deletions(-)