[PATCH v6 11/12] ARM/ARM64: KVM: Emulate PSCI v0.2 CPU_SUSPEND
From: Christoffer Dall <hidden>
Date: 2014-03-31 17:40:18
On Mon, Mar 31, 2014 at 04:16:12PM +0530, Anup Patel wrote:
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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 <redacted> Signed-off-by: Pranavkumar Sawargaonkar <redacted> --- 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
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+ 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