From: "Chang S. Bae" <chang.seok.bae@intel.com>
To: x86@kernel.org
Cc: luto@kernel.org, ak@linux.intel.com, hpa@zytor.com,
markus.t.metzger@intel.com, tony.luck@intel.com,
ravi.v.shankar@intel.com, linux-kernel@vger.kernel.org,
chang.seok.bae@intel.com
Subject: [PATCH 15/15] x86/fsgsbase/64: Enable FSGSBASE by default and add a chicken bit
Date: Mon, 19 Mar 2018 10:49:27 -0700 [thread overview]
Message-ID: <1521481767-22113-16-git-send-email-chang.seok.bae@intel.com> (raw)
In-Reply-To: <1521481767-22113-1-git-send-email-chang.seok.bae@intel.com>
From: Andy Lutomirski <luto@kernel.org>
Now that FSGSBASE is fully supported, remove unsafe_fsgsbase, enable
FSGSBASE by default, and add nofsgsbase to disable it.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
---
Documentation/admin-guide/kernel-parameters.txt | 3 +--
arch/x86/kernel/cpu/common.c | 33 +++++++++++--------------
2 files changed, 15 insertions(+), 21 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 87c2260..433dd17 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2567,8 +2567,7 @@
emulation library even if a 387 maths coprocessor
is present.
- unsafe_fsgsbase [X86] Allow FSGSBASE instructions. This will be
- replaced with a nofsgsbase flag.
+ nofsgsbase [X86] Disables FSGSBASE instructions.
no_console_suspend
[HW] Never suspend the console
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 019bdc3..f9b7eba 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -355,22 +355,21 @@ static __always_inline void setup_umip(struct cpuinfo_x86 *c)
cr4_clear_bits(X86_CR4_UMIP);
}
-/*
- * Temporary hack: FSGSBASE is unsafe until a few kernel code paths are updated.
- * This allows us to get the kernel ready incrementally. Setting
- * unsafe_fsgsbase will allow the series to be bisected if necessary.
- *
- * Once all the pieces are in place, this will go away and be replaced with
- * a nofsgsbase chicken flag.
- */
-static bool unsafe_fsgsbase;
-
-static __init int setup_unsafe_fsgsbase(char *arg)
+static __init int x86_nofsgsbase_setup(char *arg)
{
- unsafe_fsgsbase = true;
+ /* require an exact match without trailing characters */
+ if (strlen(arg))
+ return 0;
+
+ /* do not emit a message if the feature is not present */
+ if (!boot_cpu_has(X86_FEATURE_FSGSBASE))
+ return 1;
+
+ setup_clear_cpu_cap(X86_FEATURE_FSGSBASE);
+ pr_info("nofsgsbase: FSGSBASE disabled\n");
return 1;
}
-__setup("unsafe_fsgsbase", setup_unsafe_fsgsbase);
+__setup("nofsgsbase", x86_nofsgsbase_setup);
/*
* Protection Keys are not available in 32-bit mode.
@@ -1256,12 +1255,8 @@ static void identify_cpu(struct cpuinfo_x86 *c)
setup_umip(c);
/* Enable FSGSBASE instructions if available. */
- if (cpu_has(c, X86_FEATURE_FSGSBASE)) {
- if (unsafe_fsgsbase)
- cr4_set_bits(X86_CR4_FSGSBASE);
- else
- clear_cpu_cap(c, X86_FEATURE_FSGSBASE);
- }
+ if (cpu_has(c, X86_FEATURE_FSGSBASE))
+ cr4_set_bits(X86_CR4_FSGSBASE);
/*
* The vendor-specific functions might have changed features.
--
2.7.4
next prev parent reply other threads:[~2018-03-19 20:53 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-19 17:49 [PATCH 00/15] x86: Enable FSGSBASE instructions Chang S. Bae
2018-03-19 17:49 ` [PATCH 01/15] x86/fsgsbase/64: Introduce FS/GS base helper functions Chang S. Bae
2018-03-19 17:49 ` [PATCH 02/15] x86/fsgsbase/64: Make ptrace read FS/GS base accurately Chang S. Bae
2018-03-19 17:49 ` [PATCH 03/15] x86/fsgsbase/64: Use FS/GS base helpers in core dump Chang S. Bae
2018-03-19 17:49 ` [PATCH 04/15] x86/fsgsbase/64: Factor out load FS/GS segments from __switch_to Chang S. Bae
2018-03-19 17:49 ` [PATCH 05/15] x86/ptrace: A new macro to get an offset of user_regs_struct Chang S. Bae
2018-03-19 17:49 ` [PATCH 06/15] x86/fsgsbase/64: Add putregs() to handle multiple elements' setting Chang S. Bae
2018-03-19 17:49 ` [PATCH 07/15] x86/fsgsbase/64: putregs() in a reverse order Chang S. Bae
2018-03-19 17:49 ` [PATCH 08/15] x86/fsgsbase/64: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Chang S. Bae
2018-03-19 17:49 ` [PATCH 09/15] x86/fsgsbase/64: Add intrinsics/macros for FSGSBASE instructions Chang S. Bae
2018-03-19 17:49 ` [PATCH 10/15] x86/fsgsbase/64: Enable FSGSBASE instructions in helper functions Chang S. Bae
2018-03-19 17:49 ` [PATCH 11/15] x86/fsgsbase/64: Preserve FS/GS state in __switch_to if FSGSBASE is on Chang S. Bae
2018-03-19 17:49 ` [PATCH 12/15] x86/fsgsbase/64: When copying a thread, use FSGSBASE if enabled Chang S. Bae
2018-03-19 17:49 ` [PATCH 13/15] x86/fsgsbase/64: With FSGSBASE, compare GS bases on paranoid_entry Chang S. Bae
2018-03-19 20:05 ` Dave Hansen
2018-03-19 21:12 ` Bae, Chang Seok
2018-03-20 10:16 ` David Laight
2018-03-20 20:07 ` H. Peter Anvin
2018-03-20 20:36 ` Bae, Chang Seok
2018-03-21 0:36 ` Andy Lutomirski
2018-03-21 21:56 ` H. Peter Anvin
2018-03-20 14:58 ` Andy Lutomirski
2018-03-20 16:33 ` Bae, Chang Seok
2018-03-20 17:03 ` Bae, Chang Seok
2018-03-21 22:03 ` H. Peter Anvin
2018-03-22 1:37 ` Andy Lutomirski
2018-03-19 17:49 ` [PATCH 14/15] x86/fsgsbase/64: Support legacy behavior when FS/GS updated by ptracer Chang S. Bae
2018-03-20 15:04 ` Andy Lutomirski
2018-03-20 16:33 ` Bae, Chang Seok
2018-03-21 0:47 ` Andy Lutomirski
2018-03-21 7:01 ` Metzger, Markus T
2018-03-22 1:39 ` Andy Lutomirski
2018-03-21 15:11 ` Bae, Chang Seok
2018-03-22 1:40 ` Andy Lutomirski
2018-03-22 15:45 ` Bae, Chang Seok
2018-03-22 16:07 ` Andy Lutomirski
2018-03-22 16:46 ` Bae, Chang Seok
2018-03-22 16:53 ` Andy Lutomirski
2018-03-22 21:17 ` Bae, Chang Seok
2018-03-22 21:28 ` Andy Lutomirski
2018-03-19 17:49 ` Chang S. Bae [this message]
2018-03-20 15:05 ` [PATCH 00/15] x86: Enable FSGSBASE instructions Andy Lutomirski
2018-03-20 15:06 ` Andy Lutomirski
2018-03-20 16:33 ` Bae, Chang Seok
2018-03-21 0:40 ` Andy Lutomirski
2018-03-21 15:15 ` Bae, Chang Seok
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1521481767-22113-16-git-send-email-chang.seok.bae@intel.com \
--to=chang.seok.bae@intel.com \
--cc=ak@linux.intel.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=markus.t.metzger@intel.com \
--cc=ravi.v.shankar@intel.com \
--cc=tony.luck@intel.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).