Please consider s390 and (x86/arm) KVM. Once we have a few, more can
follow later, but I think its important to not only have PPC support for
Actually the s390 preemted check via sigp sense running is available for
all hypervisors (z/VM, LPAR and KVM) which implies everywhere as you can
no longer buy s390 systems without LPAR.
As Heiko already pointed out we could simply use a small inline function
that calls cpu_is_preempted from arch/s390/lib/spinlock (or
smp_vcpu_scheduled from smp.c)
Sure, and I had vague memories of Heiko's email. This patch set however
completely fails to do that trivial hooking up.
sorry for that.
I will try to work it out on x86.
x86 has no hypervisor support, and I'd like to understand the desired
semantics first, so I don't think it should block this series. In
particular, there are at least the following choices:just to avoid any misunderstanding.
1) exit to userspace (5-10.000 clock cycles best case) counts as
lock holder preemption
2) any time the vCPU thread not running counts as lock holderseems a little expensive. :(
To implement the latter you'd need a hypercall or MSR (at least as
a slow path), because the KVM preempt notifier is only active
during the KVM_RUN ioctl.