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@linaro.org Signed-off-by: Pranavkumar Sawargaonkar pranavkumar@linaro.org
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;@@ -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;-- 1.7.9.5