xen/PMU: Initialization code for Xen PMU

Map shared data structure that will hold CPU registers, VPMU context,
V/PCPU IDs of the CPU interrupted by PMU interrupt. Hypervisor fills
this information in its handler and passes it to the guest for further
processing.

Set up PMU VIRQ.

Now that perf infrastructure will assume that PMU is available on a PV
guest we need to be careful and make sure that accesses via RDPMC
instruction don't cause fatal traps by the hypervisor. Provide a nop
RDPMC handler.

For the same reason avoid issuing a warning on a write to APIC's LVTPC.

Both of these will be made functional in later patches.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

1 files changed, 170 insertions, 0 deletions

diff --git a/arch/x86/xen/pmu.c b/arch/x86/xen/pmu.c
new file mode 100644
index 000000000000..1d1ae1b874ea
--- /dev/null
+++ b/arch/x86/xen/pmu.c
@@ -0,0 +1,170 @@
+#include <linux/types.h>
+#include <linux/interrupt.h>
+
+#include <asm/xen/hypercall.h>
+#include <xen/page.h>
+#include <xen/interface/xen.h>
+#include <xen/interface/vcpu.h>
+#include <xen/interface/xenpmu.h>
+
+#include "xen-ops.h"
+#include "pmu.h"
+
+/* x86_pmu.handle_irq definition */
+#include "../kernel/cpu/perf_event.h"
+
+
+/* Shared page between hypervisor and domain */
+static DEFINE_PER_CPU(struct xen_pmu_data *, xenpmu_shared);
+#define get_xenpmu_data()    per_cpu(xenpmu_shared, smp_processor_id())
+
+/* perf callbacks */
+static int xen_is_in_guest(void)
+{
+	const struct xen_pmu_data *xenpmu_data = get_xenpmu_data();
+
+	if (!xenpmu_data) {
+		pr_warn_once("%s: pmudata not initialized\n", __func__);
+		return 0;
+	}
+
+	if (!xen_initial_domain() || (xenpmu_data->domain_id >= DOMID_SELF))
+		return 0;
+
+	return 1;
+}
+
+static int xen_is_user_mode(void)
+{
+	const struct xen_pmu_data *xenpmu_data = get_xenpmu_data();
+
+	if (!xenpmu_data) {
+		pr_warn_once("%s: pmudata not initialized\n", __func__);
+		return 0;
+	}
+
+	if (xenpmu_data->pmu.pmu_flags & PMU_SAMPLE_PV)
+		return (xenpmu_data->pmu.pmu_flags & PMU_SAMPLE_USER);
+	else
+		return !!(xenpmu_data->pmu.r.regs.cpl & 3);
+}
+
+static unsigned long xen_get_guest_ip(void)
+{
+	const struct xen_pmu_data *xenpmu_data = get_xenpmu_data();
+
+	if (!xenpmu_data) {
+		pr_warn_once("%s: pmudata not initialized\n", __func__);
+		return 0;
+	}
+
+	return xenpmu_data->pmu.r.regs.ip;
+}
+
+static struct perf_guest_info_callbacks xen_guest_cbs = {
+	.is_in_guest            = xen_is_in_guest,
+	.is_user_mode           = xen_is_user_mode,
+	.get_guest_ip           = xen_get_guest_ip,
+};
+
+/* Convert registers from Xen's format to Linux' */
+static void xen_convert_regs(const struct xen_pmu_regs *xen_regs,
+			     struct pt_regs *regs, uint64_t pmu_flags)
+{
+	regs->ip = xen_regs->ip;
+	regs->cs = xen_regs->cs;
+	regs->sp = xen_regs->sp;
+
+	if (pmu_flags & PMU_SAMPLE_PV) {
+		if (pmu_flags & PMU_SAMPLE_USER)
+			regs->cs |= 3;
+		else
+			regs->cs &= ~3;
+	} else {
+		if (xen_regs->cpl)
+			regs->cs |= 3;
+		else
+			regs->cs &= ~3;
+	}
+}
+
+irqreturn_t xen_pmu_irq_handler(int irq, void *dev_id)
+{
+	int ret = IRQ_NONE;
+	struct pt_regs regs;
+	const struct xen_pmu_data *xenpmu_data = get_xenpmu_data();
+
+	if (!xenpmu_data) {
+		pr_warn_once("%s: pmudata not initialized\n", __func__);
+		return ret;
+	}
+
+	xen_convert_regs(&xenpmu_data->pmu.r.regs, &regs,
+			 xenpmu_data->pmu.pmu_flags);
+	if (x86_pmu.handle_irq(&regs))
+		ret = IRQ_HANDLED;
+
+	return ret;
+}
+
+bool is_xen_pmu(int cpu)
+{
+	return (per_cpu(xenpmu_shared, cpu) != NULL);
+}
+
+void xen_pmu_init(int cpu)
+{
+	int err;
+	struct xen_pmu_params xp;
+	unsigned long pfn;
+	struct xen_pmu_data *xenpmu_data;
+
+	BUILD_BUG_ON(sizeof(struct xen_pmu_data) > PAGE_SIZE);
+
+	if (xen_hvm_domain())
+		return;
+
+	xenpmu_data = (struct xen_pmu_data *)get_zeroed_page(GFP_KERNEL);
+	if (!xenpmu_data) {
+		pr_err("VPMU init: No memory\n");
+		return;
+	}
+	pfn = virt_to_pfn(xenpmu_data);
+
+	xp.val = pfn_to_mfn(pfn);
+	xp.vcpu = cpu;
+	xp.version.maj = XENPMU_VER_MAJ;
+	xp.version.min = XENPMU_VER_MIN;
+	err = HYPERVISOR_xenpmu_op(XENPMU_init, &xp);
+	if (err)
+		goto fail;
+
+	per_cpu(xenpmu_shared, cpu) = xenpmu_data;
+
+	if (cpu == 0)
+		perf_register_guest_info_callbacks(&xen_guest_cbs);
+
+	return;
+
+fail:
+	pr_warn_once("Could not initialize VPMU for cpu %d, error %d\n",
+		cpu, err);
+	free_pages((unsigned long)xenpmu_data, 0);
+}
+
+void xen_pmu_finish(int cpu)
+{
+	struct xen_pmu_params xp;
+
+	if (xen_hvm_domain())
+		return;
+
+	xp.vcpu = cpu;
+	xp.version.maj = XENPMU_VER_MAJ;
+	xp.version.min = XENPMU_VER_MIN;
+
+	(void)HYPERVISOR_xenpmu_op(XENPMU_finish, &xp);
+
+	free_pages((unsigned long)per_cpu(xenpmu_shared, cpu), 0);
+	per_cpu(xenpmu_shared, cpu) = NULL;
+}