KVM: x86: retain pvclock guest stopped bit in guest memory

Otherwise its possible for an unrelated KVM_REQ_UPDATE_CLOCK (such as due to CPU
migration) to clear the bit.

Noticed by Paolo Bonzini.

Reviewed-by: Gleb Natapov <gleb@redhat.com>
Reviewed-by: Glauber Costa <glommer@parallels.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
x86: kvmclock: allocate pvclock shared memory area

We want to expose the pvclock shared memory areas, which
the hypervisor periodically updates, to userspace.

For a linear mapping from userspace, it is necessary that
entire page sized regions are used for array of pvclock
structures.

There is no such guarantee with per cpu areas, therefore move
to memblock_alloc based allocation.

Acked-by: Glauber Costa <glommer@parallels.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
x86: pvclock: make sure rdtsc doesnt speculate out of region

Originally from Jeremy Fitzhardinge.

pvclock_get_time_values, which contains the memory barriers
will be removed by next patch.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
x86: pvclock: remove pvclock_shadow_time

Originally from Jeremy Fitzhardinge.

We can copy the information directly from "struct pvclock_vcpu_time_info",
remove pvclock_shadow_time.

Reviewed-by: Glauber Costa <glommer@parallels.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
x86: pvclock: create helper for pvclock data retrieval

Originally from Jeremy Fitzhardinge.

So code can be reused.

Acked-by: Glauber Costa <glommer@parallels.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
x86: pvclock: introduce helper to read flags

Acked-by: Glauber Costa <glommer@parallels.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
x86: pvclock: add note about rdtsc barriers

As noted by Gleb, not advertising SSE2 support implies
no RDTSC barriers.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
sched: add notifier for cross-cpu migrations

Originally from Jeremy Fitzhardinge.

Acked-by: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
x86: pvclock: generic pvclock vsyscall initialization

Originally from Jeremy Fitzhardinge.

Introduce generic, non hypervisor specific, pvclock initialization
routines.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
x86: kvm guest: pvclock vsyscall support

Hook into generic pvclock vsyscall code, with the aim to
allow userspace to have visibility into pvclock data.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
x86: vdso: pvclock gettime support

Improve performance of time system calls when using Linux pvclock,
by reading time info from fixmap visible copy of pvclock data.

Originally from Jeremy Fitzhardinge.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
KVM: x86: pass host_tsc to read_l1_tsc

Allow the caller to pass host tsc value to kvm_x86_ops->read_l1_tsc().

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
time: export time information for KVM pvclock

As suggested by John, export time data similarly to how its
done by vsyscall support. This allows KVM to retrieve necessary
information to implement vsyscall support in KVM guests.

Acked-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
KVM: x86: notifier for clocksource changes

Register a notifier for clocksource change event. In case
the host switches to clock other than TSC, disable master
clock usage.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
KVM: x86: implement PVCLOCK_TSC_STABLE_BIT pvclock flag

KVM added a global variable to guarantee monotonicity in the guest.
One of the reasons for that is that the time between

	1. ktime_get_ts(&timespec);
	2. rdtscll(tsc);

Is variable. That is, given a host with stable TSC, suppose that
two VCPUs read the same time via ktime_get_ts() above.

The time required to execute 2. is not the same on those two instances
executing in different VCPUS (cache misses, interrupts...).

If the TSC value that is used by the host to interpolate when
calculating the monotonic time is the same value used to calculate
the tsc_timestamp value stored in the pvclock data structure, and
a single <system_timestamp, tsc_timestamp> tuple is visible to all
vcpus simultaneously, this problem disappears. See comment on top
of pvclock_update_vm_gtod_copy for details.

Monotonicity is then guaranteed by synchronicity of the host TSCs
and guest TSCs.

Set TSC stable pvclock flag in that case, allowing the guest to read
clock from userspace.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
KVM: x86: add kvm_arch_vcpu_postcreate callback, move TSC initialization

TSC initialization will soon make use of online_vcpus.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
KVM: x86: require matched TSC offsets for master clock

With master clock, a pvclock clock read calculates:

ret = system_timestamp + [ (rdtsc + tsc_offset) - tsc_timestamp ]

Where 'rdtsc' is the host TSC.

system_timestamp and tsc_timestamp are unique, one tuple
per VM: the "master clock".

Given a host with synchronized TSCs, its obvious that
guest TSC must be matched for the above to guarantee monotonicity.

Allow master clock usage only if guest TSCs are synchronized.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
KVM: x86: update pvclock area conditionally, on cpu migration

As requested by Glauber, do not update kvmclock area on vcpu->pcpu
migration, in case the host has stable TSC.

This is to reduce cacheline bouncing.

Acked-by: Glauber Costa <glommer@parallels.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
KVM: use is_idle_task() instead of idle_cpu() to decide when to halt in async_pf

As Frederic pointed idle_cpu() may return false even if async fault
happened in the idle task if wake up is pending. In this case the code
will try to put idle task to sleep. Fix this by using is_idle_task() to
check for idle task.

Reported-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
KVM: VMX: fix invalid cpu passed to smp_call_function_single

In loaded_vmcs_clear, loaded_vmcs->cpu is the fist parameter passed to
smp_call_function_single, if the target cpu is downing (doing cpu hot remove),
loaded_vmcs->cpu can become -1 then -1 is passed to smp_call_function_single

It can be triggered when vcpu is being destroyed, loaded_vmcs_clear is called
in the preemptionable context

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>