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 <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: hpa@zytor.com
Link: http://lkml.kernel.org/r/87oa9dwrfk.fsf@ashishki-desk.ger.corp.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index 6af7cf7..09a77db 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -136,9 +136,21 @@
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 @@
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);
- rdmsrl(MSR_IA32_RTIT_CTL, ctl);
- if (start)
- ctl |= RTIT_CTL_TRACEEN;
- else
- ctl &= ~RTIT_CTL_TRACEEN;
+ /* may be already stopped by a PMI */
+ if (!(ctl & RTIT_CTL_TRACEEN))
+ return;
+
+ 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 @@
* 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 @@
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_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 @@
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 @@
* 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;
diff --git a/arch/x86/events/intel/pt.h b/arch/x86/events/intel/pt.h
index 336878a..3abb5f5 100644
--- a/arch/x86/events/intel/pt.h
+++ b/arch/x86/events/intel/pt.h
@@ -65,6 +65,7 @@
struct pt_pmu {
struct pmu pmu;
u32 caps[PT_CPUID_REGS_NUM * PT_CPUID_LEAVES];
+ bool vmx;
};
/**
@@ -107,10 +108,12 @@
* struct pt - per-cpu pt context
* @handle: perf output handle
* @handle_nmi: do handle PT PMI on this cpu, there's an active event
+ * @vmx_on: 1 if VMX is ON on this cpu
*/
struct pt {
struct perf_output_handle handle;
int handle_nmi;
+ int vmx_on;
};
#endif /* __INTEL_PT_H__ */
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index 5a2ed3e..f353061 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -285,6 +285,10 @@
static inline void perf_check_microcode(void) { }
#endif
+#ifdef CONFIG_CPU_SUP_INTEL
+ extern void intel_pt_handle_vmx(int on);
+#endif
+
#if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_AMD)
extern void amd_pmu_enable_virt(void);
extern void amd_pmu_disable_virt(void);
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index ee1c8a9..133679d 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3103,6 +3103,8 @@
static void kvm_cpu_vmxon(u64 addr)
{
+ intel_pt_handle_vmx(1);
+
asm volatile (ASM_VMX_VMXON_RAX
: : "a"(&addr), "m"(addr)
: "memory", "cc");
@@ -3172,6 +3174,8 @@
static void kvm_cpu_vmxoff(void)
{
asm volatile (__ex(ASM_VMX_VMXOFF) : : : "cc");
+
+ intel_pt_handle_vmx(0);
}
static void hardware_disable(void)