On 5/31/23 7:15 PM, Baoquan He wrote:
On 04/26/23 at 05:08pm, Anthony Yznaga wrote:
Sending out this RFC in part to guage community interest.
This patchset implements preserved-over-kexec memory storage or PKRAM as a
method for saving memory pages of the currently executing kernel so that
they may be restored after kexec into a new kernel. The patches are adapted
from an RFC patchset sent out in 2013 by Vladimir Davydov [1]. They
introduce the PKRAM kernel API.
One use case for PKRAM is preserving guest memory and/or auxillary
supporting data (e.g. iommu data) across kexec to support reboot of the
host with minimal disruption to the guest. PKRAM provides a flexible way
for doing this without requiring that the amount of memory used by a fixed
size created a priori. Another use case is for databases to preserve their
block caches in shared memory across reboot.
If so, I have confusions, who can help clarify:
1) Why kexec reboot was introduced, what do we expect kexec reboot to
do?
2) If we need keep these data and those data, can we not reboot? They
are definitely located there w/o any concern.
3) What if systems of AI, edge computing, HPC etc also want to carry
kinds of data from userspace or kernel, system status, registers
etc when kexec reboot is needed, while enligntened by this patch?
Hi Baoquan,
Avoiding a more significant disruption from having to halt or migrate
VMs, failover services, etc. when a reboot is necessary to pick up
security fixes is one motivation for exploring preserving memory
across the reboot.
Anthony
Thanks
Baoquan
