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Message-Id: <1485365586-21653-3-git-send-email-joao.m.martins@oracle.com>
Date: Wed, 25 Jan 2017 17:33:05 +0000
From: Joao Martins <joao.m.martins@...cle.com>
To: linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org
Cc: Joao Martins <joao.m.martins@...cle.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Juergen Gross <jgross@...e.com>,
Andy Lutomirski <luto@...capital.net>
Subject: [PATCH v1 2/3] x86/xen/time: setup vcpu 0 time info page
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@...cle.com>
---
Changes since RFC:
(Comments from Boris and David)
* Remove Kconfig option
* Use get_zeroed_page/free/page
* Remove the hypercall availability check
* Unregister pvti with arg.addr.v = NULL if stable bit isn't supported.
(New)
* Set secondary copy on restore such that it works on migration.
* Drop global xen_clock variable and stash it locally on
xen_setup_vsyscall_time_info.
* WARN_ON(ret) if we fail to unregister the pvti.
---
arch/x86/xen/enlighten.c | 2 ++
arch/x86/xen/time.c | 51 ++++++++++++++++++++++++++++++++++++++++++++
arch/x86/xen/xen-ops.h | 1 +
include/xen/interface/vcpu.h | 28 ++++++++++++++++++++++++
4 files changed, 82 insertions(+)
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 51ef952..15d271d 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -270,6 +270,8 @@ void xen_vcpu_restore(void)
HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL))
BUG();
}
+
+ xen_setup_vsyscall_time_info(0);
}
static void __init xen_banner(void)
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 1e69956..e90f703 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -367,6 +367,56 @@ static const struct pv_time_ops xen_time_ops __initconst = {
.steal_clock = xen_steal_clock,
};
+int xen_setup_vsyscall_time_info(int cpu)
+{
+ struct pvclock_vsyscall_time_info *xen_clock;
+ struct vcpu_register_time_memory_area t;
+ struct pvclock_vcpu_time_info *pvti;
+ unsigned long addr;
+ u8 flags;
+ int ret;
+
+ addr = get_zeroed_page(GFP_KERNEL);
+ if (!addr)
+ return -ENOMEM;
+
+ xen_clock = (struct pvclock_vsyscall_time_info *) addr;
+ memset(xen_clock, 0, PAGE_SIZE);
+
+ t.addr.v = &xen_clock->pvti;
+
+ ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area,
+ cpu, &t);
+
+ if (ret) {
+ pr_debug("xen: cannot register vcpu_time_info err %d\n", ret);
+ free_page(addr);
+ return ret;
+ }
+
+ pvti = &xen_clock->pvti;
+ flags = pvti->flags;
+
+ if (!(flags & PVCLOCK_TSC_STABLE_BIT)) {
+ t.addr.v = NULL;
+ ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area,
+ cpu, &t);
+ if (!ret)
+ free_page(addr);
+
+ WARN_ON(ret);
+ pr_debug("xen: VCLOCK_PVCLOCK not supported\n");
+ return -ENOTSUPP;
+ }
+
+ pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
+ pvclock_set_pvti_cpu0_va(xen_clock);
+
+ xen_clocksource.archdata.vclock_mode = VCLOCK_PVCLOCK;
+
+ return 0;
+}
+
static void __init xen_time_init(void)
{
int cpu = smp_processor_id();
@@ -393,6 +443,7 @@ static void __init xen_time_init(void)
setup_force_cpu_cap(X86_FEATURE_TSC);
xen_setup_runstate_info(cpu);
+ xen_setup_vsyscall_time_info(cpu);
xen_setup_timer(cpu);
xen_setup_cpu_clockevents();
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index ac0a2b0..4036d15 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -66,6 +66,7 @@ void __init xen_vmalloc_p2m_tree(void);
void xen_init_irq_ops(void);
void xen_setup_timer(int cpu);
void xen_setup_runstate_info(int cpu);
+int xen_setup_vsyscall_time_info(int cpu);
void xen_teardown_timer(int cpu);
u64 xen_clocksource_read(void);
void xen_setup_cpu_clockevents(void);
diff --git a/include/xen/interface/vcpu.h b/include/xen/interface/vcpu.h
index 98188c8..8da788c 100644
--- a/include/xen/interface/vcpu.h
+++ b/include/xen/interface/vcpu.h
@@ -178,4 +178,32 @@ DEFINE_GUEST_HANDLE_STRUCT(vcpu_register_vcpu_info);
/* Send an NMI to the specified VCPU. @extra_arg == NULL. */
#define VCPUOP_send_nmi 11
+
+/*
+ * 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_t);
+struct vcpu_register_time_memory_area {
+ union {
+ GUEST_HANDLE(vcpu_time_info_t) h;
+ struct pvclock_vcpu_time_info *v;
+ uint64_t p;
+ } addr;
+};
+DEFINE_GUEST_HANDLE_STRUCT(vcpu_register_time_memory_area_t);
+
#endif /* __XEN_PUBLIC_VCPU_H__ */
--
2.1.4
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