x86/xen/time: setup vcpu 0 time info page

commit 2229f70b5bbb025e1394b61007938a68060afbfb upstream.

In order to support pvclock vdso on xen we need to setup the time
info page for vcpu 0 and register the page with Xen using the
VCPUOP_register_vcpu_time_memory_area hypercall. This hypercall
will also forcefully update the pvti which will set some of the
necessary flags for vdso. Afterwards we check if it supports the
PVCLOCK_TSC_STABLE_BIT flag which is mandatory for having
vdso/vsyscall support. And if so, it will set the cpu 0 pvti that
will be later on used when mapping the vdso image.

The xen headers are also updated to include the new hypercall for
registering the secondary vcpu_time_info struct.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/xen/suspend.c b/arch/x86/xen/suspend.c
index 3e3a58e..1d83152 100644 (file)
--- a/arch/x86/xen/suspend.c
+++ b/arch/x86/xen/suspend.c
@@ -22,6 +22,8 @@ static DEFINE_PER_CPU(u64, spec_ctrl);
 
 void xen_arch_pre_suspend(void)
 {
+       xen_save_time_memory_area();
+
        if (xen_pv_domain())
                xen_pv_pre_suspend();
 }
@@ -32,6 +34,8 @@ void xen_arch_post_suspend(int cancelled)
                xen_pv_post_suspend(cancelled);
        else
                xen_hvm_post_suspend(cancelled);
+
+       xen_restore_time_memory_area();
 }
 
 static void xen_vcpu_notify_restore(void *data)

diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 5687be6..efa81e7 100644 (file)
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -371,6 +371,92 @@ 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;
@@ -402,8 +488,10 @@ static void __init xen_time_init(void)
         * bit is supported hence speeding up Xen clocksource.
         */
        pvti = &__this_cpu_read(xen_vcpu)->time;
-       if (pvti->flags & PVCLOCK_TSC_STABLE_BIT)
+       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);

diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index f377e18..75011b8 100644 (file)
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -70,6 +70,8 @@ void xen_setup_runstate_info(int cpu);
 void xen_teardown_timer(int cpu);
 u64 xen_clocksource_read(void);
 void xen_setup_cpu_clockevents(void);
+void xen_save_time_memory_area(void);
+void xen_restore_time_memory_area(void);
 void __init xen_init_time_ops(void);
 void __init xen_hvm_init_time_ops(void);
 

diff --git a/include/xen/interface/vcpu.h b/include/xen/interface/vcpu.h
index 98188c8..504c716 100644 (file)
--- a/include/xen/interface/vcpu.h
+++ b/include/xen/interface/vcpu.h
@@ -178,4 +178,46 @@ DEFINE_GUEST_HANDLE_STRUCT(vcpu_register_vcpu_info);
 
 /* Send an NMI to the specified VCPU. @extra_arg == NULL. */
 #define VCPUOP_send_nmi             11
+
+/*
+ * Get the physical ID information for a pinned vcpu's underlying physical
+ * processor.  The physical ID informmation is architecture-specific.
+ * On x86: id[31:0]=apic_id, id[63:32]=acpi_id.
+ * This command returns -EINVAL if it is not a valid operation for this VCPU.
+ */
+#define VCPUOP_get_physid           12 /* arg == vcpu_get_physid_t */
+struct vcpu_get_physid {
+       uint64_t phys_id;
+};
+DEFINE_GUEST_HANDLE_STRUCT(vcpu_get_physid);
+#define xen_vcpu_physid_to_x86_apicid(physid) ((uint32_t)(physid))
+#define xen_vcpu_physid_to_x86_acpiid(physid) ((uint32_t)((physid) >> 32))
+
+/*
+ * Register a memory location to get a secondary copy of the vcpu time
+ * parameters.  The master copy still exists as part of the vcpu shared
+ * memory area, and this secondary copy is updated whenever the master copy
+ * is updated (and using the same versioning scheme for synchronisation).
+ *
+ * The intent is that this copy may be mapped (RO) into userspace so
+ * that usermode can compute system time using the time info and the
+ * tsc.  Usermode will see an array of vcpu_time_info structures, one
+ * for each vcpu, and choose the right one by an existing mechanism
+ * which allows it to get the current vcpu number (such as via a
+ * segment limit).  It can then apply the normal algorithm to compute
+ * system time from the tsc.
+ *
+ * @extra_arg == pointer to vcpu_register_time_info_memory_area structure.
+ */
+#define VCPUOP_register_vcpu_time_memory_area   13
+DEFINE_GUEST_HANDLE_STRUCT(vcpu_time_info);
+struct vcpu_register_time_memory_area {
+       union {
+               GUEST_HANDLE(vcpu_time_info) h;
+               struct pvclock_vcpu_time_info *v;
+               uint64_t p;
+       } addr;
+};
+DEFINE_GUEST_HANDLE_STRUCT(vcpu_register_time_memory_area);
+
 #endif /* __XEN_PUBLIC_VCPU_H__ */