perf/x86/kvm: Fix Host-Only/Guest-Only counting with SVM disabled

commit 1018faa6cf23b256bf25919ef203cd7c129f06f2 upstream.

It turned out that a performance counter on AMD does not
count at all when the GO or HO bit is set in the control
register and SVM is disabled in EFER.

This patch works around this issue by masking out the HO bit
in the performance counter control register when SVM is not
enabled.

The GO bit is not touched because it is only set when the
user wants to count in guest-mode only. So when SVM is
disabled the counter should not run at all and the
not-counting is the intended behaviour.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Avi Kivity <avi@redhat.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Robert Richter <robert.richter@amd.com>
Link: http://lkml.kernel.org/r/1330523852-19566-1-git-send-email-joerg.roedel@amd.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index f61c62f7d5d8252d2984c8231fec0c6409f4e83e..50d7ff2cab3eaf74dbc7db6e48f661374012fd48 100644 (file)
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -212,4 +212,12 @@ static inline perf_guest_switch_msr *perf_guest_get_msrs(int *nr)
 static inline void perf_events_lapic_init(void)        { }
 #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);
+#else
+ static inline void amd_pmu_enable_virt(void) { }
+ static inline void amd_pmu_disable_virt(void) { }
+#endif
+
 #endif /* _ASM_X86_PERF_EVENT_H */

diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h
index b9698d40ac4bdfd890f91af9e9149b93930c7329..02e02952675d059b98adaa17760862668fba0214 100644 (file)
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -146,7 +146,9 @@ struct cpu_hw_events {
        /*
         * AMD specific bits
         */
-       struct amd_nb           *amd_nb;
+       struct amd_nb                   *amd_nb;
+       /* Inverted mask of bits to clear in the perf_ctr ctrl registers */
+       u64                             perf_ctr_virt_mask;
 
        void                            *kfree_on_online;
 };
@@ -372,9 +374,11 @@ void x86_pmu_disable_all(void);
 static inline void __x86_pmu_enable_event(struct hw_perf_event *hwc,
                                          u64 enable_mask)
 {
+       u64 disable_mask = __this_cpu_read(cpu_hw_events.perf_ctr_virt_mask);
+
        if (hwc->extra_reg.reg)
                wrmsrl(hwc->extra_reg.reg, hwc->extra_reg.config);
-       wrmsrl(hwc->config_base, hwc->config | enable_mask);
+       wrmsrl(hwc->config_base, (hwc->config | enable_mask) & ~disable_mask);
 }
 
 void x86_pmu_enable_all(int added);

diff --git a/arch/x86/kernel/cpu/perf_event_amd.c b/arch/x86/kernel/cpu/perf_event_amd.c
index aeefd45697a28231399ba51143bd39832c7eeb11..f64a039f281699a09a2373269b13cd1f1da2446d 100644 (file)
--- a/arch/x86/kernel/cpu/perf_event_amd.c
+++ b/arch/x86/kernel/cpu/perf_event_amd.c
@@ -1,4 +1,5 @@
 #include <linux/perf_event.h>
+#include <linux/export.h>
 #include <linux/types.h>
 #include <linux/init.h>
 #include <linux/slab.h>
@@ -357,7 +358,9 @@ static void amd_pmu_cpu_starting(int cpu)
        struct amd_nb *nb;
        int i, nb_id;
 
-       if (boot_cpu_data.x86_max_cores < 2)
+       cpuc->perf_ctr_virt_mask = AMD_PERFMON_EVENTSEL_HOSTONLY;
+
+       if (boot_cpu_data.x86_max_cores < 2 || boot_cpu_data.x86 == 0x15)
                return;
 
        nb_id = amd_get_nb_id(cpu);
@@ -587,9 +590,9 @@ static __initconst const struct x86_pmu amd_pmu_f15h = {
        .put_event_constraints  = amd_put_event_constraints,
 
        .cpu_prepare            = amd_pmu_cpu_prepare,
-       .cpu_starting           = amd_pmu_cpu_starting,
        .cpu_dead               = amd_pmu_cpu_dead,
 #endif
+       .cpu_starting           = amd_pmu_cpu_starting,
 };
 
 __init int amd_pmu_init(void)
@@ -621,3 +624,33 @@ __init int amd_pmu_init(void)
 
        return 0;
 }
+
+void amd_pmu_enable_virt(void)
+{
+       struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
+
+       cpuc->perf_ctr_virt_mask = 0;
+
+       /* Reload all events */
+       x86_pmu_disable_all();
+       x86_pmu_enable_all(0);
+}
+EXPORT_SYMBOL_GPL(amd_pmu_enable_virt);
+
+void amd_pmu_disable_virt(void)
+{
+       struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
+
+       /*
+        * We only mask out the Host-only bit so that host-only counting works
+        * when SVM is disabled. If someone sets up a guest-only counter when
+        * SVM is disabled the Guest-only bits still gets set and the counter
+        * will not count anything.
+        */
+       cpuc->perf_ctr_virt_mask = AMD_PERFMON_EVENTSEL_HOSTONLY;
+
+       /* Reload all events */
+       x86_pmu_disable_all();
+       x86_pmu_enable_all(0);
+}
+EXPORT_SYMBOL_GPL(amd_pmu_disable_virt);

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index e32243eac2f48874ac494f5f8a27ed7fb605ebc4..94a4672a4381a869177cea7ab16e8bcb87a1ad66 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -29,6 +29,7 @@
 #include <linux/ftrace_event.h>
 #include <linux/slab.h>
 
+#include <asm/perf_event.h>
 #include <asm/tlbflush.h>
 #include <asm/desc.h>
 #include <asm/kvm_para.h>
@@ -575,6 +576,8 @@ static void svm_hardware_disable(void *garbage)
                wrmsrl(MSR_AMD64_TSC_RATIO, TSC_RATIO_DEFAULT);
 
        cpu_svm_disable();
+
+       amd_pmu_disable_virt();
 }
 
 static int svm_hardware_enable(void *garbage)
@@ -622,6 +625,8 @@ static int svm_hardware_enable(void *garbage)
 
        svm_init_erratum_383();
 
+       amd_pmu_enable_virt();
+
        return 0;
 }