I took a look at memory barriers in KVM and there are a few that are unjustified, underdocumented or wrong. While looking at irqchip_in_kernel uses (to understand the memory barriers) I also noticed one case where it is unnecessary to check for irqchip_in_kernel (patch 3).
Most of the users of irqchip_in_kernel do not need the barrier and they could check vcpu->arch.apic instead of vcpu->kvm->arch.pic. I plan to change that by introducing lapic_in_kernel(struct kvm_vcpu *), after the split irqchip patches are in which will make irqchip_in_kernel more expensive. Paolo Paolo Bonzini (4): KVM: x86: remove unnecessary memory barriers for shared MSRs KVM: document memory barriers for kvm->vcpus/kvm->online_vcpus KVM: i8254: remove unnecessary irqchip_in_kernel check KVM: x86: clean/fix memory barriers in irqchip_in_kernel arch/x86/kvm/i8254.c | 2 +- arch/x86/kvm/i8259.c | 15 +++++---------- arch/x86/kvm/irq.h | 8 ++++---- arch/x86/kvm/x86.c | 21 +++++++-------------- include/linux/kvm_host.h | 4 ++++ virt/kvm/kvm_main.c | 2 ++ 6 files changed, 23 insertions(+), 29 deletions(-) -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
