From: Roger Pau Monne <roger.pau@citrix.com>
To: xen-devel@lists.xenproject.org
Cc: Roger Pau Monne <roger.pau@citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
George Dunlap <george.dunlap@citrix.com>,
Jan Beulich <jbeulich@suse.com>, Julien Grall <julien@xen.org>,
Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>
Subject: [PATCH v3 3/4] x86/spec: fix INDIRECT_THUNK option to only be set when build-enabled
Date: Mon, 26 Feb 2024 12:07:47 +0100 [thread overview]
Message-ID: <20240226110748.80254-4-roger.pau@citrix.com> (raw)
In-Reply-To: <20240226110748.80254-1-roger.pau@citrix.com>
Attempt to provide a more helpful error message when the user attempts to set
spec-ctrl=bti-thunk option but the support is build-time disabled.
While there also adjust the command line documentation to mention
CONFIG_INDIRECT_THUNK instead of INDIRECT_THUNK.
Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
Changes since v2:
- Adjust documentation.
- Use IS_ENABLED() instead of #ifdef.
Changes since v1:
- New in this version.
---
docs/misc/xen-command-line.pandoc | 10 +++++-----
xen/arch/x86/spec_ctrl.c | 7 ++++++-
2 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc
index be76be8d5365..02896598df6f 100644
--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -2417,11 +2417,11 @@ guests to use.
performance reasons dom0 is unprotected by default. If it is necessary to
protect dom0 too, boot with `spec-ctrl=ibpb-entry`.
-If Xen was compiled with INDIRECT_THUNK support, `bti-thunk=` can be used to
-select which of the thunks gets patched into the `__x86_indirect_thunk_%reg`
-locations. The default thunk is `retpoline` (generally preferred), with the
-alternatives being `jmp` (a `jmp *%reg` gadget, minimal overhead), and
-`lfence` (an `lfence; jmp *%reg` gadget).
+If Xen was compiled with `CONFIG_INDIRECT_THUNK` support, `bti-thunk=` can be
+used to select which of the thunks gets patched into the
+`__x86_indirect_thunk_%reg` locations. The default thunk is `retpoline`
+(generally preferred), with the alternatives being `jmp` (a `jmp *%reg` gadget,
+minimal overhead), and `lfence` (an `lfence; jmp *%reg` gadget).
On hardware supporting IBRS (Indirect Branch Restricted Speculation), the
`ibrs=` option can be used to force or prevent Xen using the feature itself.
diff --git a/xen/arch/x86/spec_ctrl.c b/xen/arch/x86/spec_ctrl.c
index 5fae80774519..ca82b9e41ccd 100644
--- a/xen/arch/x86/spec_ctrl.c
+++ b/xen/arch/x86/spec_ctrl.c
@@ -241,7 +241,12 @@ static int __init cf_check parse_spec_ctrl(const char *s)
{
s += 10;
- if ( !cmdline_strcmp(s, "retpoline") )
+ if ( !IS_ENABLED(CONFIG_INDIRECT_THUNK) )
+ {
+ no_config_param("INDIRECT_THUNK", "spec-ctrl=bti-thunk", s, ss);
+ rc = -EINVAL;
+ }
+ else if ( !cmdline_strcmp(s, "retpoline") )
opt_thunk = THUNK_RETPOLINE;
else if ( !cmdline_strcmp(s, "lfence") )
opt_thunk = THUNK_LFENCE;
--
2.43.0
next prev parent reply other threads:[~2024-02-26 11:08 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-26 11:07 [PATCH v3 0/4] x86/spec: improve command line parsing Roger Pau Monne
2024-02-26 11:07 ` [PATCH v3 1/4] x86/spec: print the built-in SPECULATIVE_HARDEN_* options Roger Pau Monne
2024-02-26 12:39 ` Jan Beulich
2024-02-27 11:13 ` Roger Pau Monné
2024-02-26 11:07 ` [PATCH v3 2/4] x86/spec: fix BRANCH_HARDEN option to only be set when build-enabled Roger Pau Monne
2024-02-26 12:42 ` Jan Beulich
2024-02-26 11:07 ` Roger Pau Monne [this message]
2024-02-26 12:50 ` [PATCH v3 3/4] x86/spec: fix INDIRECT_THUNK " Jan Beulich
2024-02-27 11:18 ` Roger Pau Monné
2024-02-26 11:07 ` [PATCH v3 4/4] x86/spec: do not print thunk option selection if not built-in Roger Pau Monne
2024-02-26 12:54 ` Jan Beulich
2024-02-27 11:20 ` Roger Pau Monné
2024-02-27 13:23 ` Jan Beulich
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=20240226110748.80254-4-roger.pau@citrix.com \
--to=roger.pau@citrix.com \
--cc=andrew.cooper3@citrix.com \
--cc=george.dunlap@citrix.com \
--cc=jbeulich@suse.com \
--cc=julien@xen.org \
--cc=sstabellini@kernel.org \
--cc=wl@xen.org \
--cc=xen-devel@lists.xenproject.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.