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Haren Myneni e1b45baa2e powerpc/pseries/vas: Migration suspend waits for no in-progress open windows [ Upstream commit `0cf72f7f14` ] The hypervisor returns migration failure if all VAS windows are not closed. During pre-migration stage, vas_migration_handler() sets migration_in_progress flag and closes all windows from the list. The allocate VAS window routine checks the migration flag, setup the window and then add it to the list. So there is possibility of the migration handler missing the window that is still in the process of setup. t1: Allocate and open VAS t2: Migration event window lock vas_pseries_mutex If migration_in_progress set unlock vas_pseries_mutex return open window HCALL unlock vas_pseries_mutex Modify window HCALL lock vas_pseries_mutex setup window migration_in_progress=true Closes all windows from the list // May miss windows that are // not in the list unlock vas_pseries_mutex lock vas_pseries_mutex return if nr_closed_windows == 0 // No DLPAR CPU or migration add window to the list // Window will be added to the // list after the setup is completed unlock vas_pseries_mutex return unlock vas_pseries_mutex Close VAS window // due to DLPAR CPU or migration return -EBUSY This patch resolves the issue with the following steps: - Set the migration_in_progress flag without holding mutex. - Introduce nr_open_wins_progress counter in VAS capabilities struct - This counter tracks the number of open windows are still in progress - The allocate setup window thread closes windows if the migration is set and decrements nr_open_window_progress counter - The migration handler waits for no in-progress open windows. The code flow with the fix is as follows: t1: Allocate and open VAS t2: Migration event window lock vas_pseries_mutex If migration_in_progress set unlock vas_pseries_mutex return open window HCALL nr_open_wins_progress++ // Window opened, but not // added to the list yet unlock vas_pseries_mutex Modify window HCALL migration_in_progress=true setup window lock vas_pseries_mutex Closes all windows from the list While nr_open_wins_progress { unlock vas_pseries_mutex lock vas_pseries_mutex sleep if nr_closed_windows == 0 // Wait if any open window in or migration is not started // progress. The open window // No DLPAR CPU or migration // thread closes the window without add window to the list // adding to the list and return if nr_open_wins_progress-- // the migration is in progress. unlock vas_pseries_mutex return Close VAS window nr_open_wins_progress-- unlock vas_pseries_mutex return -EBUSY lock vas_pseries_mutex } unlock vas_pseries_mutex return Fixes: `37e6764895` ("powerpc/pseries/vas: Add VAS migration handler") Signed-off-by: Haren Myneni <haren@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/20231125235104.3405008-1-haren@linux.ibm.com Signed-off-by: Sasha Levin <sashal@kernel.org>		2024-01-10 17:16:59 +01:00
arch	powerpc/pseries/vas: Migration suspend waits for no in-progress open windows	2024-01-10 17:16:59 +01:00
block	blk-cgroup: bypass blkcg_deactivate_policy after destroying	2023-12-20 17:01:55 +01:00
certs	certs: Reference revocation list for all keyrings	2023-08-17 20:12:41 +00:00
crypto	crypto: xts - use 'spawn' for underlying single-block cipher	2024-01-10 17:16:54 +01:00
Documentation	dt-bindings: nvmem: mxs-ocotp: Document fsl,ocotp	2024-01-01 12:42:42 +00:00
drivers	dmaengine: fsl-edma: fix wrong pointer check in fsl_edma3_attach_pd()	2024-01-10 17:16:59 +01:00
fs	mm: convert DAX lock/unlock page to lock/unlock folio	2024-01-10 17:16:53 +01:00
include	crypto: hisilicon/qm - fix EQ/AEQ interrupt issue	2024-01-10 17:16:55 +01:00
init	proc: sysctl: prevent aliased sysctls from getting passed to init	2023-11-28 17:19:57 +00:00
io_uring	io_uring/cmd: fix breakage in SOCKET_URING_OP_SIOC* implementation	2023-12-20 17:01:52 +01:00
ipc	Add x86 shadow stack support	2023-08-31 12:20:12 -07:00
kernel	kernel/resource: Increment by align value in get_free_mem_region()	2024-01-10 17:16:58 +01:00
lib	maple_tree: do not preallocate nodes for slot stores	2024-01-05 15:19:43 +01:00
LICENSES	LICENSES: Add the copyleft-next-0.3.1 license	2022-11-08 15:44:01 +01:00
mm	mm/memory-failure: pass the folio and the page to collect_procs()	2024-01-10 17:16:54 +01:00
net	tcp: derive delack_max from rto_min	2024-01-10 17:16:54 +01:00
rust	rust: docs: fix logo replacement	2023-10-19 16:40:00 +02:00
samples	vfio/mtty: Overhaul mtty interrupt handling	2024-01-10 17:16:55 +01:00
scripts	scripts/checkstack.pl: match all stack sizes for s390	2023-12-20 17:01:59 +01:00
security	apparmor: Fix move_mount mediation by detecting if source is detached	2024-01-10 17:16:52 +01:00
sound	ASoC: meson: g12a-tohdmitx: Fix event generation for S/PDIF mux	2024-01-10 17:16:51 +01:00
tools	bpftool: Align output skeleton ELF code	2024-01-10 17:16:54 +01:00
usr	initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP	2023-06-06 17:54:49 +09:00
virt	ARM:	2023-09-07 13:52:20 -07:00
.clang-format	iommu: Add for_each_group_device()	2023-05-23 08:15:51 +02:00
.cocciconfig	scripts: add Linux .cocciconfig for coccinelle	2016-07-22 12:13:39 +02:00
.get_maintainer.ignore	get_maintainer: add Alan to .get_maintainer.ignore	2022-08-20 15:17:44 -07:00
.gitattributes	.gitattributes: set diff driver for Rust source code files	2023-05-31 17:48:25 +02:00
.gitignore	kbuild: rpm-pkg: rename binkernel.spec to kernel.spec	2023-07-25 00:59:33 +09:00
.mailmap	20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues	2023-10-24 09:52:16 -10:00
.rustfmt.toml	rust: add `.rustfmt.toml`	2022-09-28 09:02:20 +02:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	USB: Remove Wireless USB and UWB documentation	2023-08-09 14:17:32 +02:00
Kbuild	Kbuild updates for v6.1	2022-10-10 12:00:45 -07:00
Kconfig	kbuild: ensure full rebuild when the compiler is updated	2020-05-12 13:28:33 +09:00
MAINTAINERS	Char/Misc driver fixes for 6.6-final	2023-10-28 07:51:27 -10:00
Makefile	Linux 6.6.10	2024-01-05 15:19:45 +01:00
README	Drop all 00-INDEX files from Documentation/	2018-09-09 15:08:58 -06:00

README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.