diff options
| author | Johannes Wikner <kwikner@ethz.ch> | 2024-10-08 12:36:30 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-10-22 15:39:26 +0200 |
| commit | e7c0f8ca3bddef44aaab2aafc22c64d0e0f66165 (patch) | |
| tree | 446cb35735d8c5c8f38dcd75ac97b3f69d4fbb03 | |
| parent | 0ab77a47e3ff18889ebdb377b7ce9857008d9e80 (diff) | |
| download | linux-e7c0f8ca3bddef44aaab2aafc22c64d0e0f66165.tar.gz linux-e7c0f8ca3bddef44aaab2aafc22c64d0e0f66165.tar.bz2 linux-e7c0f8ca3bddef44aaab2aafc22c64d0e0f66165.zip | |
x86/bugs: Skip RSB fill at VMEXIT
commit 0fad2878642ec46225af2054564932745ac5c765 upstream.
entry_ibpb() is designed to follow Intel's IBPB specification regardless
of CPU. This includes invalidating RSB entries.
Hence, if IBPB on VMEXIT has been selected, entry_ibpb() as part of the
RET untraining in the VMEXIT path will take care of all BTB and RSB
clearing so there's no need to explicitly fill the RSB anymore.
[ bp: Massage commit message. ]
Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Johannes Wikner <kwikner@ethz.ch>
Cc: <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index d6e14190cf80..23f884a5d12c 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1062,6 +1062,14 @@ do_cmd_auto: case RETBLEED_MITIGATION_IBPB: setup_force_cpu_cap(X86_FEATURE_ENTRY_IBPB); mitigate_smt = true; + + /* + * There is no need for RSB filling: entry_ibpb() ensures + * all predictions, including the RSB, are invalidated, + * regardless of IBPB implementation. + */ + setup_clear_cpu_cap(X86_FEATURE_RSB_VMEXIT); + break; default: @@ -2465,6 +2473,13 @@ static void __init srso_select_mitigation(void) if (!boot_cpu_has(X86_FEATURE_ENTRY_IBPB) && has_microcode) { setup_force_cpu_cap(X86_FEATURE_IBPB_ON_VMEXIT); srso_mitigation = SRSO_MITIGATION_IBPB_ON_VMEXIT; + + /* + * There is no need for RSB filling: entry_ibpb() ensures + * all predictions, including the RSB, are invalidated, + * regardless of IBPB implementation. + */ + setup_clear_cpu_cap(X86_FEATURE_RSB_VMEXIT); } } else { pr_err("WARNING: kernel not compiled with CPU_SRSO.\n"); |