On Mon, Mar 31, 2014 at 04:16:12PM +0530, Anup Patel wrote: > This patch adds emulation of PSCI v0.2 CPU_SUSPEND function call for > KVM ARM/ARM64. This is a CPU-level function call which can suspend > current CPU or current CPU cluster. We don't have VCPU clusters in > KVM so for KVM we simply suspend the current VCPU. > > The CPU_SUSPEND emulation is not tested much because currently there > is no CPUIDLE driver in Linux kernel that uses PSCI CPU_SUSPEND. The > PSCI CPU_SUSPEND implementation in ARM64 kernel was tested using a > Simple CPUIDLE driver which is not published due to unstable DT-bindings > for PSCI. > (For more info, http://lwn.net/Articles/574950/) > > Even if we had stable DT-bindings for PSCI and CPUIDLE driver that > uses PSCI CPU_SUSPEND then still we need to define SUSPEND states > and WAKEUP events for KVM ARM/ARM64. > > Due to this, we implement CPU_SUSPEND emulation similar to WFI > (Wait-for-interrupt) emulation. > > Signed-off-by: Anup Patel <anup.patel@xxxxxxxxxx> > Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@xxxxxxxxxx> > --- > arch/arm/kvm/psci.c | 29 +++++++++++++++++++++++++---- > 1 file changed, 25 insertions(+), 4 deletions(-) > > diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c > index 85bf896..f414fd3 100644 > --- a/arch/arm/kvm/psci.c > +++ b/arch/arm/kvm/psci.c > @@ -52,6 +52,27 @@ static unsigned long psci_affinity_mask(unsigned long affinity_level) > return affinity_mask; > } > > +static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu) > +{ > + /* > + * NOTE: Currently, we don't have any wakeup events for KVM > + * so for simplicity we make VCPU suspend emulation same-as > + * WFI (Wait-for-interrupt) emulation. If you implement it like WFI, we do have wake-up events: Namely interrupts. > + * > + * To do this we simply update VCPU registers as-per state > + * info provided via r1 - r3 (or x1 - x3) and block the > + * VCPU for irqs. > + */ > + if (*vcpu_reg(vcpu, 1) & (0x1UL << 16)) { > + /* Update return pc and r0 for power-down state. */ > + *vcpu_pc(vcpu) = *vcpu_reg(vcpu, 2); > + *vcpu_reg(vcpu, 0) = *vcpu_reg(vcpu, 3); > + } Hmm, this looks wrong. This looks like you're respecting the power-down state request but not resetting the CPU. What I was saying before was that if you implement this as kvm_vcpu_block(), just like WFI, then you need to preserve all state, ignore power-down state requests and treat them as suspend states, implement them as WFI, and put a big fat comment here explaining why this is architecturally valid (by referring to the PSCI 0.2 spec) and what the semantics of doing that is. -Christoffer > + kvm_vcpu_block(vcpu); > + > + return PSCI_RET_SUCCESS; > +} > + > static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu) > { > vcpu->arch.pause = true; > @@ -195,6 +216,10 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu) > */ > val = 2; > break; > + case PSCI_0_2_FN_CPU_SUSPEND: > + case PSCI_0_2_FN64_CPU_SUSPEND: > + val = kvm_psci_vcpu_suspend(vcpu); > + break; > case PSCI_0_2_FN_CPU_OFF: > kvm_psci_vcpu_off(vcpu); > val = PSCI_RET_SUCCESS; > @@ -232,10 +257,6 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu) > val = PSCI_RET_SUCCESS; > ret = 0; > break; > - case PSCI_0_2_FN_CPU_SUSPEND: > - case PSCI_0_2_FN64_CPU_SUSPEND: > - val = PSCI_RET_NOT_SUPPORTED; > - break; > default: > return -EINVAL; > } > -- > 1.7.9.5 > _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
