xen/PMU: Sysfs interface for setting Xen PMU mode

Set Xen's PMU mode via /sys/hypervisor/pmu/pmu_mode. Add XENPMU hypercall.

Signed-off-by: Boris Ostrovsky <[e-mail]>
Reviewed-by: Konrad Rzeszutek Wilk <[e-mail]>
Signed-off-by: David Vrabel <[e-mail]>

Documentation/ABI/testing/sysfs-hypervisor-pmu

···
+What:		/sys/hypervisor/pmu/pmu_mode
+Date:		August 2015
+KernelVersion:	4.3
+Contact:	Boris Ostrovsky <[e-mail]>
+Description:
+		Describes mode that Xen's performance-monitoring unit (PMU)
+		uses. Accepted values are
+			"off"  -- PMU is disabled
+			"self" -- The guest can profile itself
+			"hv"   -- The guest can profile itself and, if it is
+				  privileged (e.g. dom0), the hypervisor
+			"all" --  The guest can profile itself, the hypervisor
+				  and all other guests. Only available to
+				  privileged guests.
+
+What:           /sys/hypervisor/pmu/pmu_features
+Date:           August 2015
+KernelVersion:  4.3
+Contact:        Boris Ostrovsky <[e-mail]>
+Description:
+		Describes Xen PMU features (as an integer). A set bit indicates
+		that the corresponding feature is enabled. See
+		include/xen/interface/xenpmu.h for available features

arch/x86/include/asm/xen/hypercall.h

···
 	return _hypercall1(int, tmem_op, op);
 }
 
+static inline int
+HYPERVISOR_xenpmu_op(unsigned int op, void *arg)
+{
+	return _hypercall2(int, xenpmu_op, op, arg);
+}
+
 static inline void
 MULTI_fpu_taskswitch(struct multicall_entry *mcl, int set)
 {

arch/x86/xen/Kconfig

···
 	depends on PARAVIRT
 	select PARAVIRT_CLOCK
 	select XEN_HAVE_PVMMU
+	select XEN_HAVE_VPMU
 	depends on X86_64 || (X86_32 && X86_PAE)
 	depends on X86_TSC
 	help

drivers/xen/Kconfig

···
           Exports hypervisor symbols (along with their types and addresses) via
           /proc/xen/xensyms file, similar to /proc/kallsyms
 
+config XEN_HAVE_VPMU
+       bool
+
 endmenu

drivers/xen/sys-hypervisor.c

···
 #include <xen/xenbus.h>
 #include <xen/interface/xen.h>
 #include <xen/interface/version.h>
+#ifdef CONFIG_XEN_HAVE_VPMU
+#include <xen/interface/xenpmu.h>
+#endif
 
 #define HYPERVISOR_ATTR_RO(_name) \
 static struct hyp_sysfs_attr  _name##_attr = __ATTR_RO(_name)
···
 	sysfs_remove_group(hypervisor_kobj, &xen_properties_group);
 }
 
+#ifdef CONFIG_XEN_HAVE_VPMU
+struct pmu_mode {
+	const char *name;
+	uint32_t mode;
+};
+
+static struct pmu_mode pmu_modes[] = {
+	{"off", XENPMU_MODE_OFF},
+	{"self", XENPMU_MODE_SELF},
+	{"hv", XENPMU_MODE_HV},
+	{"all", XENPMU_MODE_ALL}
+};
+
+static ssize_t pmu_mode_store(struct hyp_sysfs_attr *attr,
+			      const char *buffer, size_t len)
+{
+	int ret;
+	struct xen_pmu_params xp;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(pmu_modes); i++) {
+		if (strncmp(buffer, pmu_modes[i].name, len - 1) == 0) {
+			xp.val = pmu_modes[i].mode;
+			break;
+		}
+	}
+
+	if (i == ARRAY_SIZE(pmu_modes))
+		return -EINVAL;
+
+	xp.version.maj = XENPMU_VER_MAJ;
+	xp.version.min = XENPMU_VER_MIN;
+	ret = HYPERVISOR_xenpmu_op(XENPMU_mode_set, &xp);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static ssize_t pmu_mode_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	int ret;
+	struct xen_pmu_params xp;
+	int i;
+	uint32_t mode;
+
+	xp.version.maj = XENPMU_VER_MAJ;
+	xp.version.min = XENPMU_VER_MIN;
+	ret = HYPERVISOR_xenpmu_op(XENPMU_mode_get, &xp);
+	if (ret)
+		return ret;
+
+	mode = (uint32_t)xp.val;
+	for (i = 0; i < ARRAY_SIZE(pmu_modes); i++) {
+		if (mode == pmu_modes[i].mode)
+			return sprintf(buffer, "%s\n", pmu_modes[i].name);
+	}
+
+	return -EINVAL;
+}
+HYPERVISOR_ATTR_RW(pmu_mode);
+
+static ssize_t pmu_features_store(struct hyp_sysfs_attr *attr,
+				  const char *buffer, size_t len)
+{
+	int ret;
+	uint32_t features;
+	struct xen_pmu_params xp;
+
+	ret = kstrtou32(buffer, 0, &features);
+	if (ret)
+		return ret;
+
+	xp.val = features;
+	xp.version.maj = XENPMU_VER_MAJ;
+	xp.version.min = XENPMU_VER_MIN;
+	ret = HYPERVISOR_xenpmu_op(XENPMU_feature_set, &xp);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static ssize_t pmu_features_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	int ret;
+	struct xen_pmu_params xp;
+
+	xp.version.maj = XENPMU_VER_MAJ;
+	xp.version.min = XENPMU_VER_MIN;
+	ret = HYPERVISOR_xenpmu_op(XENPMU_feature_get, &xp);
+	if (ret)
+		return ret;
+
+	return sprintf(buffer, "0x%x\n", (uint32_t)xp.val);
+}
+HYPERVISOR_ATTR_RW(pmu_features);
+
+static struct attribute *xen_pmu_attrs[] = {
+	&pmu_mode_attr.attr,
+	&pmu_features_attr.attr,
+	NULL
+};
+
+static const struct attribute_group xen_pmu_group = {
+	.name = "pmu",
+	.attrs = xen_pmu_attrs,
+};
+
+static int __init xen_pmu_init(void)
+{
+	return sysfs_create_group(hypervisor_kobj, &xen_pmu_group);
+}
+
+static void xen_pmu_destroy(void)
+{
+	sysfs_remove_group(hypervisor_kobj, &xen_pmu_group);
+}
+#endif
+
 static int __init hyper_sysfs_init(void)
 {
 	int ret;
···
 	ret = xen_properties_init();
 	if (ret)
 		goto prop_out;
-
+#ifdef CONFIG_XEN_HAVE_VPMU
+	if (xen_initial_domain()) {
+		ret = xen_pmu_init();
+		if (ret) {
+			xen_properties_destroy();
+			goto prop_out;
+		}
+	}
+#endif
 	goto out;
 
 prop_out:
···
 
 static void __exit hyper_sysfs_exit(void)
 {
+#ifdef CONFIG_XEN_HAVE_VPMU
+	xen_pmu_destroy();
+#endif
 	xen_properties_destroy();
 	xen_compilation_destroy();
 	xen_sysfs_uuid_destroy();

include/xen/interface/xen.h

···
 #define __HYPERVISOR_kexec_op             37
 #define __HYPERVISOR_tmem_op              38
 #define __HYPERVISOR_xc_reserved_op       39 /* reserved for XenClient */
+#define __HYPERVISOR_xenpmu_op            40
 
 /* Architecture-specific hypercall definitions. */
 #define __HYPERVISOR_arch_0               48

include/xen/interface/xenpmu.h

···
+#ifndef __XEN_PUBLIC_XENPMU_H__
+#define __XEN_PUBLIC_XENPMU_H__
+
+#include "xen.h"
+
+#define XENPMU_VER_MAJ    0
+#define XENPMU_VER_MIN    1
+
+/*
+ * ` enum neg_errnoval
+ * ` HYPERVISOR_xenpmu_op(enum xenpmu_op cmd, struct xenpmu_params *args);
+ *
+ * @cmd  == XENPMU_* (PMU operation)
+ * @args == struct xenpmu_params
+ */
+/* ` enum xenpmu_op { */
+#define XENPMU_mode_get        0 /* Also used for getting PMU version */
+#define XENPMU_mode_set        1
+#define XENPMU_feature_get     2
+#define XENPMU_feature_set     3
+#define XENPMU_init            4
+#define XENPMU_finish          5
+
+/* ` } */
+
+/* Parameters structure for HYPERVISOR_xenpmu_op call */
+struct xen_pmu_params {
+	/* IN/OUT parameters */
+	struct {
+		uint32_t maj;
+		uint32_t min;
+	} version;
+	uint64_t val;
+
+	/* IN parameters */
+	uint32_t vcpu;
+	uint32_t pad;
+};
+
+/* PMU modes:
+ * - XENPMU_MODE_OFF:   No PMU virtualization
+ * - XENPMU_MODE_SELF:  Guests can profile themselves
+ * - XENPMU_MODE_HV:    Guests can profile themselves, dom0 profiles
+ *                      itself and Xen
+ * - XENPMU_MODE_ALL:   Only dom0 has access to VPMU and it profiles
+ *                      everyone: itself, the hypervisor and the guests.
+ */
+#define XENPMU_MODE_OFF           0
+#define XENPMU_MODE_SELF          (1<<0)
+#define XENPMU_MODE_HV            (1<<1)
+#define XENPMU_MODE_ALL           (1<<2)
+
+/*
+ * PMU features:
+ * - XENPMU_FEATURE_INTEL_BTS: Intel BTS support (ignored on AMD)
+ */
+#define XENPMU_FEATURE_INTEL_BTS  1
+
+#endif /* __XEN_PUBLIC_XENPMU_H__ */