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