From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Yao Zi <me@ziyao.cc>, Thomas Gleixner <tglx@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH] x86/cpu/centaur: Disable X86_FEATURE_FSGSBASE on Zhaoxin C4600
Date: Sun, 1 Mar 2026 16:29:13 +0000 [thread overview]
Message-ID: <05f84fa5-d0df-4bab-80a6-5ff2c418b5ec@citrix.com> (raw)
In-Reply-To: <20260228173704.62460-1-me@ziyao.cc>
On 28/02/2026 5:37 pm, Yao Zi wrote:
> Zhaoxin C4600, which names itself as CentaurHauls, claims
> X86_FEATURE_FSGSBASE support in CPUID, while execution of fsgsbase-
> related instructions fails with #UD exception. This will cause kernel
> to crash early in current_save_fsgs().
#UD is the expected behaviour of the FSGS instructions if they're not
enabled.
Are you saying that this specific CPU enumerates FSGSBASE in CPUID, and
permits setting CR4.FSGSBASE (without #GP for a reserved bit), and the
FSGS instructions still do not function?
What happens if you read CR4 back after trying to set the bit?
~Andrew
next prev parent reply other threads:[~2026-03-01 16:29 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-28 17:37 [PATCH] x86/cpu/centaur: Disable X86_FEATURE_FSGSBASE on Zhaoxin C4600 Yao Zi
2026-02-28 19:06 ` Borislav Petkov
2026-03-01 9:27 ` Yao Zi
2026-03-01 18:37 ` David Laight
2026-03-02 5:09 ` Yao Zi
2026-03-01 0:33 ` Dave Hansen
2026-03-01 9:10 ` Yao Zi
2026-03-01 10:28 ` Borislav Petkov
2026-03-01 16:29 ` Andrew Cooper [this message]
2026-03-02 5:08 ` Yao Zi
2026-03-02 9:36 ` Andrew Cooper
2026-03-05 9:03 ` Tony W Wang-oc
2026-03-05 12:40 ` Andrew Cooper
2026-03-05 14:04 ` Yao Zi
2026-03-05 14:10 ` Andrew Cooper
2026-03-05 14:11 ` David Laight
2026-03-05 16:20 ` Dave Hansen
2026-03-12 2:14 ` Tony W Wang-oc
2026-03-12 15:52 ` Dave Hansen
2026-03-17 7:41 ` Tony W Wang-oc
2026-03-17 15:21 ` Dave Hansen
2026-03-18 3:44 ` Tony W Wang-oc
-- strict thread matches above, loose matches on Subject: below --
2026-03-05 20:26 Christian Ludloff
2026-03-12 2:18 ` Tony W Wang-oc
2026-03-12 16:31 ` Christian Ludloff
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