From 9fb9a5434f1c888e4cd8fd1cb573973939eddfa9 Mon Sep 17 00:00:00 2001 From: Joao Martins Date: Wed, 8 Nov 2017 17:19:57 +0000 Subject: 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 Reviewed-by: Juergen Gross Reviewed-by: Boris Ostrovsky Signed-off-by: Boris Ostrovsky Signed-off-by: Juergen Gross Signed-off-by: Greg Kroah-Hartman --- arch/x86/xen/suspend.c | 4 +++ arch/x86/xen/time.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++++- arch/x86/xen/xen-ops.h | 2 ++ 3 files changed, 95 insertions(+), 1 deletion(-) (limited to 'arch/x86') diff --git a/arch/x86/xen/suspend.c b/arch/x86/xen/suspend.c index 3e3a58ea669e..1d83152c761b 100644 --- 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 5687be6f5ca5..efa81e736f43 100644 --- 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 f377e1820c6c..75011b80660f 100644 --- 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); -- cgit v1.2.3