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Pu Wen 009767dbf4 x86/sev: Check SME/SEV support in CPUID first 
The first two bits of the CPUID leaf 0x8000001F EAX indicate whether SEV
or SME is supported, respectively. It's better to check whether SEV or
SME is actually supported before accessing the MSR_AMD64_SEV to check
whether SEV or SME is enabled.

This is both a bare-metal issue and a guest/VM issue. Since the first
generation Hygon Dhyana CPU doesn't support the MSR_AMD64_SEV, reading that
MSR results in a #GP - either directly from hardware in the bare-metal
case or via the hypervisor (because the RDMSR is actually intercepted)
in the guest/VM case, resulting in a failed boot. And since this is very
early in the boot phase, rdmsrl_safe()/native_read_msr_safe() can't be
used.

So check the CPUID bits first, before accessing the MSR.

 [ tlendacky: Expand and improve commit message. ]
 [ bp: Massage commit message. ]

Fixes: eab696d8e8 ("x86/sev: Do not require Hypervisor CPUID bit for SEV guests")
Signed-off-by: Pu Wen <puwen@hygon.cn>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: <stable@vger.kernel.org> # v5.10+
Link: https://lkml.kernel.org/r/20210602070207.2480-1-puwen@hygon.cn
2021-06-04 18:39:09 +02:00
arch x86/sev: Check SME/SEV support in CPUID first 2021-06-04 18:39:09 +02:00
block block-5.13-2021-05-22 2021-05-22 07:40:34 -10:00
certs Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
crypto for-5.13/drivers-2021-04-27 2021-04-28 14:39:37 -07:00
Documentation powerpc fixes for 5.13 #4 2021-05-23 06:07:33 -10:00
drivers dmaengine: idxd: Use cpu_feature_enabled() 2021-06-03 16:32:59 +02:00
fs userfaultfd: hugetlbfs: fix new flag usage in error path 2021-05-22 15:09:07 -10:00
include linux/bits.h: fix compilation error with GENMASK 2021-05-22 15:09:07 -10:00
init Merge branch 'akpm' (patches from Andrew) 2021-05-07 00:34:51 -07:00
ipc ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry 2021-05-22 15:09:07 -10:00
kernel Two locking fixes: 2021-05-23 06:30:08 -10:00
lib lib: kunit: suppress a compilation warning of frame size 2021-05-22 15:09:07 -10:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm userfaultfd: hugetlbfs: fix new flag usage in error path 2021-05-22 15:09:07 -10:00
net Char/misc driver fixes for 5.13-rc3 2021-05-20 06:31:52 -10:00
samples Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
scripts kbuild: dummy-tools: adjust to stricter stackprotector check 2021-05-17 12:10:03 +09:00
security trusted-keys: match tpm_get_ops on all return paths 2021-05-12 22:36:37 +03:00
sound sound fixes for 5.13-rc3 2021-05-20 06:42:21 -10:00
tools powerpc fixes for 5.13 #4 2021-05-23 06:07:33 -10:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt kvm: Cap halt polling at kvm->max_halt_poll_ns 2021-05-07 06:06:22 -04:00
.clang-format cxl for 5.12 2021-02-24 09:38:36 -08:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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 .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap Merge drm/drm-fixes into drm-misc-fixes 2021-05-11 13:35:52 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: move Murali Karicheri to credits 2021-04-29 15:47:30 -07:00
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 proc: remove Alexey from MAINTAINERS 2021-05-22 15:09:07 -10:00
Makefile Linux 5.13-rc3 2021-05-23 11:42:48 -10:00
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.