diff options
| author | Pawan Gupta <pawan.kumar.gupta@linux.intel.com> | 2022-07-14 16:15:35 -0700 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2022-07-20 19:24:53 +0200 |
| commit | eb23b5ef9131e6d65011de349a4d25ef1b3d4314 (patch) | |
| tree | ecf5304ceb8f67c1a18be0710c4950efdea4819e | |
| parent | 65cdf0d623bedf0e069bb64ed52e8bb20105e2ba (diff) | |
| download | linux-gpio-intel-eb23b5ef9131e6d65011de349a4d25ef1b3d4314.tar.gz | |
x86/bugs: Warn when "ibrs" mitigation is selected on Enhanced IBRS parts
IBRS mitigation for spectre_v2 forces write to MSR_IA32_SPEC_CTRL at
every kernel entry/exit. On Enhanced IBRS parts setting
MSR_IA32_SPEC_CTRL[IBRS] only once at boot is sufficient. MSR writes at
every kernel entry/exit incur unnecessary performance loss.
When Enhanced IBRS feature is present, print a warning about this
unnecessary performance loss.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/2a5eaf54583c2bfe0edc4fea64006656256cca17.1657814857.git.pawan.kumar.gupta@linux.intel.com
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 78c9082242a9b8..6454bc767f0fdf 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -975,6 +975,7 @@ static inline const char *spectre_v2_module_string(void) { return ""; } #define SPECTRE_V2_LFENCE_MSG "WARNING: LFENCE mitigation is not recommended for this CPU, data leaks possible!\n" #define SPECTRE_V2_EIBRS_EBPF_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS on, data leaks possible via Spectre v2 BHB attacks!\n" #define SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS+LFENCE mitigation and SMT, data leaks possible via Spectre v2 BHB attacks!\n" +#define SPECTRE_V2_IBRS_PERF_MSG "WARNING: IBRS mitigation selected on Enhanced IBRS CPU, this may cause unnecessary performance loss\n" #ifdef CONFIG_BPF_SYSCALL void unpriv_ebpf_notify(int new_state) @@ -1415,6 +1416,8 @@ static void __init spectre_v2_select_mitigation(void) case SPECTRE_V2_IBRS: setup_force_cpu_cap(X86_FEATURE_KERNEL_IBRS); + if (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) + pr_warn(SPECTRE_V2_IBRS_PERF_MSG); break; case SPECTRE_V2_LFENCE: |