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

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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>
This commit is contained in:
Joao Martins 2017-11-08 17:19:57 +00:00 committed by Boris Ostrovsky
parent b888808093
commit 2229f70b5b
4 changed files with 137 additions and 1 deletions
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4
arch/x86/xen/suspend.c
View File

@ -16,6 +16,8 @@
void xen_arch_pre_suspend(void)
{
xen_save_time_memory_area();
if (xen_pv_domain())
xen_pv_pre_suspend();
}
@ -26,6 +28,8 @@ 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)

90
arch/x86/xen/time.c
View File

@ -370,6 +370,92 @@ 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;
@ -401,8 +487,10 @@ 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);

2
arch/x86/xen/xen-ops.h
View File

@ -69,6 +69,8 @@ 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);

42
include/xen/interface/vcpu.h
View File

@ -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__ */