From 1c5ac21a0e9bab7fc45d0ba9e11623e9ad99d02e Mon Sep 17 00:00:00 2001 From: Alexander Shishkin Date: Tue, 29 Mar 2016 17:43:10 +0300 Subject: perf/x86/intel/pt: Don't die on VMXON Some versions of Intel PT do not support tracing across VMXON, more specifically, VMXON will clear TraceEn control bit and any attempt to set it before VMXOFF will throw a #GP, which in the current state of things will crash the kernel. Namely: $ perf record -e intel_pt// kvm -nographic on such a machine will kill it. To avoid this, notify the intel_pt driver before VMXON and after VMXOFF so that it knows when not to enable itself. Signed-off-by: Alexander Shishkin Signed-off-by: Peter Zijlstra (Intel) Cc: Arnaldo Carvalho de Melo Cc: Arnaldo Carvalho de Melo Cc: Borislav Petkov Cc: Gleb Natapov Cc: Jiri Olsa Cc: Paolo Bonzini Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Cc: hpa@zytor.com Link: http://lkml.kernel.org/r/87oa9dwrfk.fsf@ashishki-desk.ger.corp.intel.com Signed-off-by: Ingo Molnar --- arch/x86/events/intel/pt.c | 75 +++++++++++++++++++++++++++++++++++++++------- 1 file changed, 64 insertions(+), 11 deletions(-) (limited to 'arch/x86/events/intel/pt.c') diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c index 6af7cf71d6b2..09a77dbc73c9 100644 --- a/arch/x86/events/intel/pt.c +++ b/arch/x86/events/intel/pt.c @@ -136,9 +136,21 @@ static int __init pt_pmu_hw_init(void) struct dev_ext_attribute *de_attrs; struct attribute **attrs; size_t size; + u64 reg; int ret; long i; + if (boot_cpu_has(X86_FEATURE_VMX)) { + /* + * Intel SDM, 36.5 "Tracing post-VMXON" says that + * "IA32_VMX_MISC[bit 14]" being 1 means PT can trace + * post-VMXON. + */ + rdmsrl(MSR_IA32_VMX_MISC, reg); + if (reg & BIT(14)) + pt_pmu.vmx = true; + } + attrs = NULL; for (i = 0; i < PT_CPUID_LEAVES; i++) { @@ -269,20 +281,23 @@ static void pt_config(struct perf_event *event) reg |= (event->attr.config & PT_CONFIG_MASK); + event->hw.config = reg; wrmsrl(MSR_IA32_RTIT_CTL, reg); } -static void pt_config_start(bool start) +static void pt_config_stop(struct perf_event *event) { - u64 ctl; + u64 ctl = READ_ONCE(event->hw.config); + + /* may be already stopped by a PMI */ + if (!(ctl & RTIT_CTL_TRACEEN)) + return; - rdmsrl(MSR_IA32_RTIT_CTL, ctl); - if (start) - ctl |= RTIT_CTL_TRACEEN; - else - ctl &= ~RTIT_CTL_TRACEEN; + ctl &= ~RTIT_CTL_TRACEEN; wrmsrl(MSR_IA32_RTIT_CTL, ctl); + WRITE_ONCE(event->hw.config, ctl); + /* * A wrmsr that disables trace generation serializes other PT * registers and causes all data packets to be written to memory, @@ -291,8 +306,7 @@ static void pt_config_start(bool start) * The below WMB, separating data store and aux_head store matches * the consumer's RMB that separates aux_head load and data load. */ - if (!start) - wmb(); + wmb(); } static void pt_config_buffer(void *buf, unsigned int topa_idx, @@ -942,11 +956,17 @@ void intel_pt_interrupt(void) if (!ACCESS_ONCE(pt->handle_nmi)) return; - pt_config_start(false); + /* + * If VMX is on and PT does not support it, don't touch anything. + */ + if (READ_ONCE(pt->vmx_on)) + return; if (!event) return; + pt_config_stop(event); + buf = perf_get_aux(&pt->handle); if (!buf) return; @@ -983,6 +1003,35 @@ void intel_pt_interrupt(void) } } +void intel_pt_handle_vmx(int on) +{ + struct pt *pt = this_cpu_ptr(&pt_ctx); + struct perf_event *event; + unsigned long flags; + + /* PT plays nice with VMX, do nothing */ + if (pt_pmu.vmx) + return; + + /* + * VMXON will clear RTIT_CTL.TraceEn; we need to make + * sure to not try to set it while VMX is on. Disable + * interrupts to avoid racing with pmu callbacks; + * concurrent PMI should be handled fine. + */ + local_irq_save(flags); + WRITE_ONCE(pt->vmx_on, on); + + if (on) { + /* prevent pt_config_stop() from writing RTIT_CTL */ + event = pt->handle.event; + if (event) + event->hw.config = 0; + } + local_irq_restore(flags); +} +EXPORT_SYMBOL_GPL(intel_pt_handle_vmx); + /* * PMU callbacks */ @@ -992,6 +1041,9 @@ static void pt_event_start(struct perf_event *event, int mode) struct pt *pt = this_cpu_ptr(&pt_ctx); struct pt_buffer *buf = perf_get_aux(&pt->handle); + if (READ_ONCE(pt->vmx_on)) + return; + if (!buf || pt_buffer_is_full(buf, pt)) { event->hw.state = PERF_HES_STOPPED; return; @@ -1014,7 +1066,8 @@ static void pt_event_stop(struct perf_event *event, int mode) * see comment in intel_pt_interrupt(). */ ACCESS_ONCE(pt->handle_nmi) = 0; - pt_config_start(false); + + pt_config_stop(event); if (event->hw.state == PERF_HES_STOPPED) return; -- cgit