diff options
Diffstat (limited to '0028-x86-spec-fix-INDIRECT_THUNK-option-to-only-be-set-wh.patch')
| -rw-r--r-- | 0028-x86-spec-fix-INDIRECT_THUNK-option-to-only-be-set-wh.patch | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/0028-x86-spec-fix-INDIRECT_THUNK-option-to-only-be-set-wh.patch b/0028-x86-spec-fix-INDIRECT_THUNK-option-to-only-be-set-wh.patch new file mode 100644 index 0000000..dfbf516 --- /dev/null +++ b/0028-x86-spec-fix-INDIRECT_THUNK-option-to-only-be-set-wh.patch @@ -0,0 +1,67 @@ +From 693455c3c370e535eb6cd065800ff91e147815fa Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= <roger.pau@citrix.com> +Date: Tue, 5 Mar 2024 11:58:04 +0100 +Subject: [PATCH 28/67] x86/spec: fix INDIRECT_THUNK option to only be set when + build-enabled +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +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> +Reviewed-by: Jan Beulich <jbeulich@suse.com> +master commit: 8441fa806a3b778867867cd0159fa1722e90397e +master date: 2024-02-27 14:58:20 +0100 +--- + 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 05f613c71c..2006697226 100644 +--- a/docs/misc/xen-command-line.pandoc ++++ b/docs/misc/xen-command-line.pandoc +@@ -2378,11 +2378,11 @@ 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 93f1cf3bb5..098fa3184d 100644 +--- a/xen/arch/x86/spec_ctrl.c ++++ b/xen/arch/x86/spec_ctrl.c +@@ -253,7 +253,12 @@ 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", s - 10, ss); ++ rc = -EINVAL; ++ } ++ else if ( !cmdline_strcmp(s, "retpoline") ) + opt_thunk = THUNK_RETPOLINE; + else if ( !cmdline_strcmp(s, "lfence") ) + opt_thunk = THUNK_LFENCE; +-- +2.44.0 + |