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1 | From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 | |
2 | From: Peter Zijlstra <peterz@infradead.org> | |
3 | Date: Sun, 14 Jan 2018 11:27:13 +0100 | |
4 | Subject: [PATCH] x86,perf: Disable intel_bts when PTI | |
5 | MIME-Version: 1.0 | |
6 | Content-Type: text/plain; charset=UTF-8 | |
7 | Content-Transfer-Encoding: 8bit | |
8 | ||
9 | commit 99a9dc98ba52267ce5e062b52de88ea1f1b2a7d8 upstream. | |
10 | ||
11 | The intel_bts driver does not use the 'normal' BTS buffer which is exposed | |
12 | through the cpu_entry_area but instead uses the memory allocated for the | |
13 | perf AUX buffer. | |
14 | ||
15 | This obviously comes apart when using PTI because then the kernel mapping; | |
16 | which includes that AUX buffer memory; disappears. Fixing this requires to | |
17 | expose a mapping which is visible in all context and that's not trivial. | |
18 | ||
19 | As a quick fix disable this driver when PTI is enabled to prevent | |
20 | malfunction. | |
21 | ||
22 | Fixes: 385ce0ea4c07 ("x86/mm/pti: Add Kconfig") | |
23 | Reported-by: Vince Weaver <vincent.weaver@maine.edu> | |
24 | Reported-by: Robert Święcki <robert@swiecki.net> | |
25 | Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> | |
26 | Signed-off-by: Thomas Gleixner <tglx@linutronix.de> | |
27 | Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> | |
28 | Cc: greg@kroah.com | |
29 | Cc: hughd@google.com | |
30 | Cc: luto@amacapital.net | |
31 | Cc: Vince Weaver <vince@deater.net> | |
32 | Cc: torvalds@linux-foundation.org | |
33 | Cc: stable@vger.kernel.org | |
34 | Link: https://lkml.kernel.org/r/20180114102713.GB6166@worktop.programming.kicks-ass.net | |
35 | Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> | |
36 | Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com> | |
37 | --- | |
38 | arch/x86/events/intel/bts.c | 18 ++++++++++++++++++ | |
39 | 1 file changed, 18 insertions(+) | |
40 | ||
41 | diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c | |
42 | index ddd8d3516bfc..9a62e6fce0e0 100644 | |
43 | --- a/arch/x86/events/intel/bts.c | |
44 | +++ b/arch/x86/events/intel/bts.c | |
45 | @@ -582,6 +582,24 @@ static __init int bts_init(void) | |
46 | if (!boot_cpu_has(X86_FEATURE_DTES64) || !x86_pmu.bts) | |
47 | return -ENODEV; | |
48 | ||
49 | + if (boot_cpu_has(X86_FEATURE_PTI)) { | |
50 | + /* | |
51 | + * BTS hardware writes through a virtual memory map we must | |
52 | + * either use the kernel physical map, or the user mapping of | |
53 | + * the AUX buffer. | |
54 | + * | |
55 | + * However, since this driver supports per-CPU and per-task inherit | |
56 | + * we cannot use the user mapping since it will not be availble | |
57 | + * if we're not running the owning process. | |
58 | + * | |
59 | + * With PTI we can't use the kernal map either, because its not | |
60 | + * there when we run userspace. | |
61 | + * | |
62 | + * For now, disable this driver when using PTI. | |
63 | + */ | |
64 | + return -ENODEV; | |
65 | + } | |
66 | + | |
67 | bts_pmu.capabilities = PERF_PMU_CAP_AUX_NO_SG | PERF_PMU_CAP_ITRACE | | |
68 | PERF_PMU_CAP_EXCLUSIVE; | |
69 | bts_pmu.task_ctx_nr = perf_sw_context; | |
70 | -- | |
71 | 2.14.2 | |
72 |