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Thadeu Lima de Souza Cascardo 571c30b1a8 x86/bugs: Do not enable IBPB at firmware entry when IBPB is not available
Some cloud hypervisors do not provide IBPB on very recent CPU processors,
including AMD processors affected by Retbleed.

Using IBPB before firmware calls on such systems would cause a GPF at boot
like the one below. Do not enable such calls when IBPB support is not
present.

  EFI Variables Facility v0.08 2004-May-17
  general protection fault, maybe for address 0x1: 0000 [#1] PREEMPT SMP NOPTI
  CPU: 0 PID: 24 Comm: kworker/u2:1 Not tainted 5.19.0-rc8+ #7
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
  Workqueue: efi_rts_wq efi_call_rts
  RIP: 0010:efi_call_rts
  Code: e8 37 33 58 ff 41 bf 48 00 00 00 49 89 c0 44 89 f9 48 83 c8 01 4c 89 c2 48 c1 ea 20 66 90 b9 49 00 00 00 b8 01 00 00 00 31 d2 <0f> 30 e8 7b 9f 5d ff e8 f6 f8 ff ff 4c 89 f1 4c 89 ea 4c 89 e6 48
  RSP: 0018:ffffb373800d7e38 EFLAGS: 00010246
  RAX: 0000000000000001 RBX: 0000000000000006 RCX: 0000000000000049
  RDX: 0000000000000000 RSI: ffff94fbc19d8fe0 RDI: ffff94fbc1b2b300
  RBP: ffffb373800d7e70 R08: 0000000000000000 R09: 0000000000000000
  R10: 000000000000000b R11: 000000000000000b R12: ffffb3738001fd78
  R13: ffff94fbc2fcfc00 R14: ffffb3738001fd80 R15: 0000000000000048
  FS:  0000000000000000(0000) GS:ffff94fc3da00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: ffff94fc30201000 CR3: 000000006f610000 CR4: 00000000000406f0
  Call Trace:
   <TASK>
   ? __wake_up
   process_one_work
   worker_thread
   ? rescuer_thread
   kthread
   ? kthread_complete_and_exit
   ret_from_fork
   </TASK>
  Modules linked in:

Fixes: 28a99e95f5 ("x86/amd: Use IBPB for firmware calls")
Reported-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20220728122602.2500509-1-cascardo@canonical.com
2022-07-29 10:02:35 +02:00
Documentation * Check for invalid flags to KVM_CAP_X86_USER_SPACE_MSR 2022-07-23 10:22:26 -07:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
arch x86/bugs: Do not enable IBPB at firmware entry when IBPB is not available 2022-07-29 10:02:35 +02:00
block block: fix missing blkcg_bio_issue_init 2022-07-14 10:54:49 -06:00
certs certs: make system keyring depend on x509 parser 2022-07-24 12:53:55 -07:00
crypto crypto: s390 - do not depend on CRYPTO_HW for SIMD implementations 2022-07-06 20:04:06 -07:00
drivers - Make retbleed mitigations 64-bit only (32-bit will need a bit more 2022-07-24 09:40:17 -07:00
fs io_uring-5.19-2022-07-21 2022-07-22 12:47:09 -07:00
include * Check for invalid flags to KVM_CAP_X86_USER_SPACE_MSR 2022-07-23 10:22:26 -07:00
init gcc-12: disable '-Warray-bounds' universally for now 2022-06-09 10:11:12 -07:00
ipc ipc: Free mq_sysctls if ipc namespace creation failed 2022-06-22 17:47:41 -05:00
kernel x86/configs: Update configs in x86_debug.config 2022-07-27 18:09:11 +02:00
lib ubsan: disable UBSAN_DIV_ZERO for clang 2022-07-14 15:45:26 -07:00
mm mm: split huge PUD on wp_huge_pud fallback 2022-07-03 15:42:33 -07:00
net net/sched: cls_api: Fix flow action initialization 2022-07-20 10:54:27 +01:00
samples Fixes and minor clean ups for tracing: 2022-07-12 16:17:40 -07:00
scripts scripts/gdb: Fix gdb 'lx-symbols' command 2022-07-21 10:40:55 -07:00
security lockdown: Fix kexec lockdown bypass with ima policy 2022-07-20 09:56:48 -07:00
sound ASoC: Drop Rockchip BCLK management for v5.19 2022-07-15 12:31:07 +02:00
tools * Check for invalid flags to KVM_CAP_X86_USER_SPACE_MSR 2022-07-23 10:22:26 -07:00
usr Not a lot of material this cycle. Many singleton patches against various 2022-05-27 11:22:03 -07:00
virt KVM: x86: disable preemption around the call to kvm_arch_vcpu_{un|}blocking 2022-06-09 10:52:20 -04:00
.clang-format clang-format: Fix space after for_each macros 2022-05-20 19:27:16 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore kbuild: split the second line of *.mod into *.usyms 2022-05-08 03:16:59 +09:00
.mailmap cxl fixes for 5.19-rc6 2022-07-08 12:55:25 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: mark ARM/PALM TREO SUPPORT orphan 2022-07-07 15:17:00 +02:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Pin control fixes for the v5.19 kernel cycle: 2022-07-22 12:24:04 -07:00
Makefile Linux 5.19-rc8 2022-07-24 13:26:27 -07:00
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.