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Mark Rutland 2836c72e8d arm64/arm: xen: enlighten: Fix KPTI checks 
[ Upstream commit 20f3b8eafe ]

When KPTI is in use, we cannot register a runstate region as XEN
requires that this is always a valid VA, which we cannot guarantee. Due
to this, xen_starting_cpu() must avoid registering each CPU's runstate
region, and xen_guest_init() must avoid setting up features that depend
upon it.

We tried to ensure that in commit:

  f88af7229f (" xen/arm: do not setup the runstate info page if kpti is enabled")

... where we added checks for xen_kernel_unmapped_at_usr(), which wraps
arm64_kernel_unmapped_at_el0() on arm64 and is always false on 32-bit
arm.

Unfortunately, as xen_guest_init() is an early_initcall, this happens
before secondary CPUs are booted and arm64 has finalized the
ARM64_UNMAP_KERNEL_AT_EL0 cpucap which backs
arm64_kernel_unmapped_at_el0(), and so this can subsequently be set as
secondary CPUs are onlined. On a big.LITTLE system where the boot CPU
does not require KPTI but some secondary CPUs do, this will result in
xen_guest_init() intializing features that depend on the runstate
region, and xen_starting_cpu() registering the runstate region on some
CPUs before KPTI is subsequent enabled, resulting the the problems the
aforementioned commit tried to avoid.

Handle this more robsutly by deferring the initialization of the
runstate region until secondary CPUs have been initialized and the
ARM64_UNMAP_KERNEL_AT_EL0 cpucap has been finalized. The per-cpu work is
moved into a new hotplug starting function which is registered later
when we're certain that KPTI will not be used.

Fixes: f88af7229f ("xen/arm: do not setup the runstate info page if kpti is enabled")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Bertrand Marquis <bertrand.marquis@arm.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2023-11-20 11:52:00 +01:00
arch arm64/arm: xen: enlighten: Fix KPTI checks 2023-11-20 11:52:00 +01:00
block blk-throttle: check for overflow in calculate_bytes_allowed 2023-11-02 09:35:29 +01:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-02-09 11:28:11 +01:00
crypto crypto: lrw,xts - Replace strlcpy with strscpy 2023-09-23 11:11:01 +02:00
Documentation dt-bindings: mmc: sdhci-msm: correct minimum number of clocks 2023-10-25 12:03:13 +02:00
drivers drm/bridge: lt9611uxc: fix the race in the error path 2023-11-20 11:52:00 +01:00
fs pstore/platform: Add check for kstrdup 2023-11-20 11:51:50 +01:00
include arm64/arm: xen: enlighten: Fix KPTI checks 2023-11-20 11:52:00 +01:00
init sched/psi: Select KERNFS as needed 2023-09-13 09:42:28 +02:00
io_uring io_uring/kbuf: Allow the full buffer id space for provided buffers 2023-11-20 11:52:00 +01:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel bpf: Fix unnecessary -EBUSY from htab_lock_bucket 2023-11-20 11:51:55 +01:00
lib maple_tree: add GFP_KERNEL to allocations in mas_expected_entries() 2023-11-02 09:35:24 +01:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm vfs: fix readahead(2) on block devices 2023-11-20 11:51:50 +01:00
net ipv6: avoid atomic fragment on GSO packets 2023-11-20 11:51:55 +01:00
rust rust: allocator: Prevent mis-aligned allocation 2023-08-11 12:08:18 +02:00
samples fprobe: Pass entry_data to handlers 2023-10-25 12:03:12 +02:00
scripts kallsyms: Reduce the memory occupied by kallsyms_seqs_of_names[] 2023-10-25 12:03:16 +02:00
security KEYS: trusted: Remove redundant static calls usage 2023-10-19 23:08:50 +02:00
sound ASoC: SOF: sof-pci-dev: Fix community key quirk detection 2023-11-08 14:11:05 +01:00
tools net: skb_find_text: Ignore patterns extending past 'to' 2023-11-20 11:51:54 +01:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt kvm/vfio: ensure kvg instance stays around in kvm_vfio_group_add() 2023-09-13 09:42:46 +02:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.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: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
.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 MAINTAINERS: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
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 devlink: move code to a dedicated directory 2023-08-30 16:11:00 +02:00
Makefile Linux 6.1.62 2023-11-08 14:11:05 +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.