On Sat, Apr 07, 2018 at 10:54:22AM +0100, Marc Zyngier wrote: > On Fri, 06 Apr 2018 16:01:04 +0100, > Dave Martin wrote: > > Hi Dave, > > > > > This patch refactors KVM to align the host and guest FPSIMD > > save/restore logic with each other for arm64. This reduces the > > number of redundant save/restore operations that must occur, and > > reduces the common-case IRQ blackout time during guest exit storms > > by saving the host state lazily and optimising away the need to > > restore the host state before returning to the run loop. > > > > Four hooks are defined in order to enable this: > > > > * kvm_arch_vcpu_run_map_fp(): > > Called on PID change to map necessary bits of current to Hyp. > > > > * kvm_arch_vcpu_load_fp(): > > Set up FP/SIMD for entering the KVM run loop (parse as > > "vcpu_load fp"). > > > > * kvm_arch_vcpu_park_fp(): > > Get FP/SIMD into a safe state for re-enabling interrupts after a > > guest exit back to the run loop. > > It would be good if you could outline what this hook does, and what > "safe state" means in this context.
[...] > > diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c > > index d3af3f4..cf0f457 100644 > > --- a/virt/kvm/arm/arm.c > > +++ b/virt/kvm/arm/arm.c > > @@ -362,10 +362,12 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int > > cpu) > > kvm_arm_set_running_vcpu(vcpu); > > kvm_vgic_load(vcpu); > > kvm_timer_vcpu_load(vcpu); > > + kvm_arch_vcpu_load_fp(vcpu); > > Can't find this function. [...] > > @@ -772,6 +774,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, > > struct kvm_run *run) > > if (static_branch_unlikely(&userspace_irqchip_in_use)) > > kvm_timer_sync_hwstate(vcpu); > > > > + kvm_arch_vcpu_park_fp(vcpu); > > This isn't defined either. I have the feeling that you've missed a > "git add" at some point. > > > + > > /* > > * We may have taken a host interrupt in HYP mode (ie > > * while executing the guest). This interrupt is still > > @@ -816,16 +820,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, > > struct kvm_run *run) > > return ret; > > } [...] > The structure seems quite sensible, and I'm looking forward to seeing > the missing bits. Also, it looks like this was done on top of > 4.16. I'm afraid 4.17 is going to bring a number of conflicts, but > nothing that should have any material impact. Hmmm, looks like I dropped an added file when flattening my draft series. See separate repost -- sorry about that. I've kept it on v4.16 just while things stabilise. Cheers ---Dave _______________________________________________ kvmarm mailing list firstname.lastname@example.org https://lists.cs.columbia.edu/mailman/listinfo/kvmarm