This is a note to let you know that I've just added the patch titled
x86,perf: Disable intel_bts when PTI
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-perf-disable-intel_bts-when-pti.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 99a9dc98ba52267ce5e062b52de88ea1f1b2a7d8 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Sun, 14 Jan 2018 11:27:13 +0100
Subject: x86,perf: Disable intel_bts when PTI
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
commit 99a9dc98ba52267ce5e062b52de88ea1f1b2a7d8 upstream.
The intel_bts driver does not use the 'normal' BTS buffer which is exposed
through the cpu_entry_area but instead uses the memory allocated for the
perf AUX buffer.
This obviously comes apart when using PTI because then the kernel mapping;
which includes that AUX buffer memory; disappears. Fixing this requires to
expose a mapping which is visible in all context and that's not trivial.
As a quick fix disable this driver when PTI is enabled to prevent
malfunction.
Fixes: 385ce0ea4c07 ("x86/mm/pti: Add Kconfig")
Reported-by: Vince Weaver <vincent.weaver@xxxxxxxxx>
Reported-by: Robert Święcki <robert@xxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: greg@xxxxxxxxx
Cc: hughd@xxxxxxxxxx
Cc: luto@xxxxxxxxxxxxxx
Cc: Vince Weaver <vince@xxxxxxxxxx>
Cc: torvalds@xxxxxxxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20180114102713.GB6166@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/events/intel/bts.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
--- a/arch/x86/events/intel/bts.c
+++ b/arch/x86/events/intel/bts.c
@@ -582,6 +582,24 @@ static __init int bts_init(void)
if (!boot_cpu_has(X86_FEATURE_DTES64) || !x86_pmu.bts)
return -ENODEV;
+ if (boot_cpu_has(X86_FEATURE_PTI)) {
+ /*
+ * BTS hardware writes through a virtual memory map we must
+ * either use the kernel physical map, or the user mapping of
+ * the AUX buffer.
+ *
+ * However, since this driver supports per-CPU and per-task inherit
+ * we cannot use the user mapping since it will not be availble
+ * if we're not running the owning process.
+ *
+ * With PTI we can't use the kernal map either, because its not
+ * there when we run userspace.
+ *
+ * For now, disable this driver when using PTI.
+ */
+ return -ENODEV;
+ }
+
bts_pmu.capabilities = PERF_PMU_CAP_AUX_NO_SG | PERF_PMU_CAP_ITRACE |
PERF_PMU_CAP_EXCLUSIVE;
bts_pmu.task_ctx_nr = perf_sw_context;
Patches currently in stable-queue which might be from peterz@xxxxxxxxxxxxx are
queue-4.14/x86-spectre-add-boot-time-option-to-select-spectre-v2-mitigation.patch
queue-4.14/x86-retpoline-irq32-convert-assembler-indirect-jumps.patch
queue-4.14/objtool-detect-jumps-to-retpoline-thunks.patch
queue-4.14/x86-pti-unbreak-efi-old_memmap.patch
queue-4.14/x86-cpufeatures-add-x86_bug_spectre_v.patch
queue-4.14/x86-retpoline-hyperv-convert-assembler-indirect-jumps.patch
queue-4.14/membarrier-disable-preemption-when-calling-smp_call_function_many.patch
queue-4.14/x86-mm-pti-remove-dead-logic-in-pti_user_pagetable_walk.patch
queue-4.14/x86-retpoline-entry-convert-entry-assembler-indirect-jumps.patch
queue-4.14/x86-pti-fix-pcid-and-sanitize-defines.patch
queue-4.14/x86-cpu-amd-make-lfence-a-serializing-instruction.patch
queue-4.14/x86-retpoline-ftrace-convert-ftrace-assembler-indirect-jumps.patch
queue-4.14/objtool-allow-alternatives-to-be-ignored.patch
queue-4.14/x86-cpu-implement-cpu-vulnerabilites-sysfs-functions.patch
queue-4.14/x86-retpoline-crypto-convert-crypto-assembler-indirect-jumps.patch
queue-4.14/selftests-x86-add-test_vsyscall.patch
queue-4.14/x86-retpoline-xen-convert-xen-hypercall-indirect-jumps.patch
queue-4.14/x86-retpoline-checksum32-convert-assembler-indirect-jumps.patch
queue-4.14/x86-pti-make-unpoison-of-pgd-for-trusted-boot-work-for-real.patch
queue-4.14/sysfs-cpu-add-vulnerability-folder.patch
queue-4.14/x86-retpoline-fill-return-stack-buffer-on-vmexit.patch
queue-4.14/x86-retpoline-remove-compile-time-warning.patch
queue-4.14/x86-alternatives-fix-optimize_nops-checking.patch
queue-4.14/x86-cpu-amd-use-lfence_rdtsc-in-preference-to-mfence_rdtsc.patch
queue-4.14/x86-retpoline-add-initial-retpoline-support.patch
queue-4.14/x86-perf-disable-intel_bts-when-pti.patch