Merge tag 'for-linus-4.15-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen updates from Juergen Gross:
 "Xen features and fixes for v4.15-rc1

  Apart from several small fixes it contains the following features:

   - a series by Joao Martins to add vdso support of the pv clock
     interface

   - a series by Juergen Gross to add support for Xen pv guests to be
     able to run on 5 level paging hosts

   - a series by Stefano Stabellini adding the Xen pvcalls frontend
     driver using a paravirtualized socket interface"

* tag 'for-linus-4.15-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip: (34 commits)
  xen/pvcalls: fix potential endless loop in pvcalls-front.c
  xen/pvcalls: Add MODULE_LICENSE()
  MAINTAINERS: xen, kvm: track pvclock-abi.h changes
  x86/xen/time: setup vcpu 0 time info page
  x86/xen/time: set pvclock flags on xen_time_init()
  x86/pvclock: add setter for pvclock_pvti_cpu0_va
  ptp_kvm: probe for kvm guest availability
  xen/privcmd: remove unused variable pageidx
  xen: select grant interface version
  xen: update arch/x86/include/asm/xen/cpuid.h
  xen: add grant interface version dependent constants to gnttab_ops
  xen: limit grant v2 interface to the v1 functionality
  xen: re-introduce support for grant v2 interface
  xen: support priv-mapping in an HVM tools domain
  xen/pvcalls: remove redundant check for irq >= 0
  xen/pvcalls: fix unsigned less than zero error check
  xen/time: Return -ENODEV from xen_get_wallclock()
  xen/pvcalls-front: mark expected switch fall-through
  xen: xenbus_probe_frontend: mark expected switch fall-throughs
  xen/time: do not decrease steal time after live migration on xen
  ...

1 files changed, 98 insertions, 1 deletions

diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 80c2a4bdf230..29163c43ebbd 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -75,7 +75,7 @@ static void xen_get_wallclock(struct timespec *now)
 
 static int xen_set_wallclock(const struct timespec *now)
 {
-	return -1;
+	return -ENODEV;
 }
 
 static int xen_pvclock_gtod_notify(struct notifier_block *nb,
@@ -371,8 +371,95 @@ static const struct pv_time_ops xen_time_ops __initconst = {
 	.steal_clock = xen_steal_clock,
 };
 
+static struct pvclock_vsyscall_time_info *xen_clock __read_mostly;
+
+void xen_save_time_memory_area(void)
+{
+	struct vcpu_register_time_memory_area t;
+	int ret;
+
+	if (!xen_clock)
+		return;
+
+	t.addr.v = NULL;
+
+	ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area, 0, &t);
+	if (ret != 0)
+		pr_notice("Cannot save secondary vcpu_time_info (err %d)",
+			  ret);
+	else
+		clear_page(xen_clock);
+}
+
+void xen_restore_time_memory_area(void)
+{
+	struct vcpu_register_time_memory_area t;
+	int ret;
+
+	if (!xen_clock)
+		return;
+
+	t.addr.v = &xen_clock->pvti;
+
+	ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area, 0, &t);
+
+	/*
+	 * We don't disable VCLOCK_PVCLOCK entirely if it fails to register the
+	 * secondary time info with Xen or if we migrated to a host without the
+	 * necessary flags. On both of these cases what happens is either
+	 * process seeing a zeroed out pvti or seeing no PVCLOCK_TSC_STABLE_BIT
+	 * bit set. Userspace checks the latter and if 0, it discards the data
+	 * in pvti and fallbacks to a system call for a reliable timestamp.
+	 */
+	if (ret != 0)
+		pr_notice("Cannot restore secondary vcpu_time_info (err %d)",
+			  ret);
+}
+
+static void xen_setup_vsyscall_time_info(void)
+{
+	struct vcpu_register_time_memory_area t;
+	struct pvclock_vsyscall_time_info *ti;
+	int ret;
+
+	ti = (struct pvclock_vsyscall_time_info *)get_zeroed_page(GFP_KERNEL);
+	if (!ti)
+		return;
+
+	t.addr.v = &ti->pvti;
+
+	ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area, 0, &t);
+	if (ret) {
+		pr_notice("xen: VCLOCK_PVCLOCK not supported (err %d)\n", ret);
+		free_page((unsigned long)ti);
+		return;
+	}
+
+	/*
+	 * If primary time info had this bit set, secondary should too since
+	 * it's the same data on both just different memory regions. But we
+	 * still check it in case hypervisor is buggy.
+	 */
+	if (!(ti->pvti.flags & PVCLOCK_TSC_STABLE_BIT)) {
+		t.addr.v = NULL;
+		ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area,
+					 0, &t);
+		if (!ret)
+			free_page((unsigned long)ti);
+
+		pr_notice("xen: VCLOCK_PVCLOCK not supported (tsc unstable)\n");
+		return;
+	}
+
+	xen_clock = ti;
+	pvclock_set_pvti_cpu0_va(xen_clock);
+
+	xen_clocksource.archdata.vclock_mode = VCLOCK_PVCLOCK;
+}
+
 static void __init xen_time_init(void)
 {
+	struct pvclock_vcpu_time_info *pvti;
 	int cpu = smp_processor_id();
 	struct timespec tp;
 
@@ -396,6 +483,16 @@ static void __init xen_time_init(void)
 
 	setup_force_cpu_cap(X86_FEATURE_TSC);
 
+	/*
+	 * We check ahead on the primary time info if this
+	 * bit is supported hence speeding up Xen clocksource.
+	 */
+	pvti = &__this_cpu_read(xen_vcpu)->time;
+	if (pvti->flags & PVCLOCK_TSC_STABLE_BIT) {
+		pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
+		xen_setup_vsyscall_time_info();
+	}
+
 	xen_setup_runstate_info(cpu);
 	xen_setup_timer(cpu);
 	xen_setup_cpu_clockevents();