[PATCH v6 14/15] KVM: ARM: Power State Coordination Interface implementation

Christoffer Dall
2013-01-16T17:59:20Z

From: Marc Zyngier <marc.zyngier@arm.com>

Implement the PSCI specification (ARM DEN 0022A) to control
virtual CPUs being "powered" on or off.

PSCI/KVM is detected using the KVM_CAP_ARM_PSCI capability.

A virtual CPU can now be initialized in a "powered off" state,
using the KVM_ARM_VCPU_POWER_OFF feature flag.

The guest can use either SMC or HVC to execute a PSCI function.

Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>
---
Documentation/virtual/kvm/api.txt | 4 +
arch/arm/include/asm/kvm_emulate.h | 5 ++
arch/arm/include/asm/kvm_host.h | 5 +-
arch/arm/include/asm/kvm_psci.h | 23 ++++++++
arch/arm/include/uapi/asm/kvm.h | 16 +++++
arch/arm/kvm/Makefile | 2 -
arch/arm/kvm/arm.c | 28 +++++++++-
arch/arm/kvm/psci.c | 105 ++++++++++++++++++++++++++++++++++++
include/uapi/linux/kvm.h | 1
9 files changed, 184 insertions(+), 5 deletions(-)
create mode 100644 arch/arm/include/asm/kvm_psci.h
create mode 100644 arch/arm/kvm/psci.c

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 38066a7a..c25439a 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -2185,6 +2185,10 @@ return ENOEXEC for that vcpu.
Note that because some registers reflect machine topology, all vcpus
should be created before this ioctl is invoked.

+Possible features:
+ - KVM_ARM_VCPU_POWER_OFF: Starts the CPU in a power-off state.
+ Depends on KVM_CAP_ARM_PSCI.
+

4.78 KVM_GET_REG_LIST

diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h
index 4c1a073..ba07de9 100644
--- a/arch/arm/include/asm/kvm_emulate.h
+++ b/arch/arm/include/asm/kvm_emulate.h
@@ -32,6 +32,11 @@ void kvm_inject_undefined(struct kvm_vcpu *vcpu);
void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr);
void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr);

+static inline bool vcpu_mode_is_32bit(struct kvm_vcpu *vcpu)
+{
+ return 1;
+}
+
static inline u32 *vcpu_pc(struct kvm_vcpu *vcpu)
{
return (u32 *)&vcpu->arch.regs.usr_regs.ARM_pc;
diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index e65fc96..c9ba918 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -30,7 +30,7 @@
#define KVM_COALESCED_MMIO_PAGE_OFFSET 1
#define KVM_HAVE_ONE_REG

-#define KVM_VCPU_MAX_FEATURES 0
+#define KVM_VCPU_MAX_FEATURES 1

/* We don't currently support large pages. */
#define KVM_HPAGE_GFN_SHIFT(x) 0
@@ -100,6 +100,9 @@ struct kvm_vcpu_arch {
int last_pcpu;
cpumask_t require_dcache_flush;

+ /* Don't run the guest: see copy_current_insn() */
+ bool pause;
+
/* IO related fields */
struct kvm_decode mmio_decode;

diff --git a/arch/arm/include/asm/kvm_psci.h b/arch/arm/include/asm/kvm_psci.h
new file mode 100644
index 0000000..9a83d98
--- /dev/null
+++ b/arch/arm/include/asm/kvm_psci.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2012 - ARM Ltd
+ * Author: Marc Zyngier <marc.zyngier@arm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __ARM_KVM_PSCI_H__
+#define __ARM_KVM_PSCI_H__
+
+bool kvm_psci_call(struct kvm_vcpu *vcpu);
+
+#endif /* __ARM_KVM_PSCI_H__ */
diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
index bbb6b23..3303ff5 100644
--- a/arch/arm/include/uapi/asm/kvm.h
+++ b/arch/arm/include/uapi/asm/kvm.h
@@ -65,6 +65,8 @@ struct kvm_regs {
#define KVM_ARM_TARGET_CORTEX_A15 0
#define KVM_ARM_NUM_TARGETS 1

+#define KVM_ARM_VCPU_POWER_OFF 0 /* CPU is started in OFF state */
+
struct kvm_vcpu_init {
__u32 target;
__u32 features[7];
@@ -145,4 +147,18 @@ struct kvm_arch_memory_slot {
/* Highest supported SPI, from VGIC_NR_IRQS */
#define KVM_ARM_IRQ_GIC_MAX 127

+/* PSCI interface */
+#define KVM_PSCI_FN_BASE 0x95c1ba5e
+#define KVM_PSCI_FN(n) (KVM_PSCI_FN_BASE + (n))
+
+#define KVM_PSCI_FN_CPU_SUSPEND KVM_PSCI_FN(0)
+#define KVM_PSCI_FN_CPU_OFF KVM_PSCI_FN(1)
+#define KVM_PSCI_FN_CPU_ON KVM_PSCI_FN(2)
+#define KVM_PSCI_FN_MIGRATE KVM_PSCI_FN(3)
+
+#define KVM_PSCI_RET_SUCCESS 0
+#define KVM_PSCI_RET_NI ((unsigned long)-1)
+#define KVM_PSCI_RET_INVAL ((unsigned long)-2)
+#define KVM_PSCI_RET_DENIED ((unsigned long)-3)
+
#endif /* __ARM_KVM_H__ */
diff --git a/arch/arm/kvm/Makefile b/arch/arm/kvm/Makefile
index 1e45cd9..ea27987 100644
--- a/arch/arm/kvm/Makefile
+++ b/arch/arm/kvm/Makefile
@@ -18,4 +18,4 @@ kvm-arm-y = $(addprefix ../../../virt/kvm/, kvm_main.o coalesced_mmio.o)

obj-y += kvm-arm.o init.o interrupts.o
obj-y += arm.o guest.o mmu.o emulate.o reset.o
-obj-y += coproc.o coproc_a15.o mmio.o
+obj-y += coproc.o coproc_a15.o mmio.o psci.o
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 3168b9d..6ff5337 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -43,6 +43,7 @@
#include <asm/kvm_mmu.h>
#include <asm/kvm_emulate.h>
#include <asm/kvm_coproc.h>
+#include <asm/kvm_psci.h>
#include <asm/opcodes.h>

#ifdef REQUIRES_VIRT
@@ -160,6 +161,7 @@ int kvm_dev_ioctl_check_extension(long ext)
case KVM_CAP_SYNC_MMU:
case KVM_CAP_DESTROY_MEMORY_REGION_WORKS:
case KVM_CAP_ONE_REG:
+ case KVM_CAP_ARM_PSCI:
r = 1;
break;
case KVM_CAP_COALESCED_MMIO:
@@ -443,13 +445,17 @@ static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run)
trace_kvm_hvc(*vcpu_pc(vcpu), *vcpu_reg(vcpu, 0),
vcpu->arch.hsr & HSR_HVC_IMM_MASK);

+ if (kvm_psci_call(vcpu))
+ return 1;
+
return 1;
}

static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
- /* We don't support SMC; don't do that. */
- kvm_debug("smc: at %08x", *vcpu_pc(vcpu));
+ if (!kvm_psci_call(vcpu))
+ return 1;
+
kvm_inject_undefined(vcpu);
return 1;
}
@@ -588,6 +594,16 @@ static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu)
return 0;

vcpu->arch.has_run_once = true;
+
+ /*
+ * Handle the "start in power-off" case by calling into the
+ * PSCI code.
+ */
+ if (test_and_clear_bit(KVM_ARM_VCPU_POWER_OFF, vcpu->arch.features)) {
+ *vcpu_reg(vcpu, 0) = KVM_PSCI_FN_CPU_OFF;
+ kvm_psci_call(vcpu);
+ }
+
return 0;
}

@@ -656,7 +672,13 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
kvm_guest_enter();
vcpu->mode = IN_GUEST_MODE;

- ret = kvm_call_hyp(__kvm_vcpu_run, vcpu);
+ smp_mb(); /* set mode before reading vcpu->arch.pause */
+ if (unlikely(vcpu->arch.pause)) {
+ /* This means ignore, try again. */
+ ret = ARM_EXCEPTION_IRQ;
+ } else {
+ ret = kvm_call_hyp(__kvm_vcpu_run, vcpu);
+ }

vcpu->mode = OUTSIDE_GUEST_MODE;
vcpu->arch.last_pcpu = smp_processor_id();
diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
new file mode 100644
index 0000000..6be3687
--- /dev/null
+++ b/arch/arm/kvm/psci.c
@@ -0,0 +1,105 @@
+/*
+ * Copyright (C) 2012 - ARM Ltd
+ * Author: Marc Zyngier <marc.zyngier@arm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/kvm_host.h>
+#include <linux/wait.h>
+
+#include <asm/kvm_emulate.h>
+#include <asm/kvm_psci.h>
+
+/*
+ * This is an implementation of the Power State Coordination Interface
+ * as described in ARM document number ARM DEN 0022A.
+ */
+
+static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu)
+{
+ wait_queue_head_t *wq = kvm_arch_vcpu_wq(vcpu);
+
+ vcpu->arch.pause = true;
+
+ wait_event_interruptible(*wq, !vcpu->arch.pause);
+}
+
+static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
+{
+ struct kvm *kvm = source_vcpu->kvm;
+ struct kvm_vcpu *vcpu;
+ wait_queue_head_t *wq;
+ unsigned long cpu_id;
+ phys_addr_t target_pc;
+
+ cpu_id = *vcpu_reg(source_vcpu, 1);
+ if (vcpu_mode_is_32bit(source_vcpu))
+ cpu_id &= ~((u32) 0);
+
+ if (cpu_id >= atomic_read(&kvm->online_vcpus))
+ return KVM_PSCI_RET_INVAL;
+
+ target_pc = *vcpu_reg(source_vcpu, 2);
+
+ vcpu = kvm_get_vcpu(kvm, cpu_id);
+
+ wq = kvm_arch_vcpu_wq(vcpu);
+ if (!waitqueue_active(wq))
+ return KVM_PSCI_RET_INVAL;
+
+ kvm_reset_vcpu(vcpu);
+ *vcpu_pc(vcpu) = target_pc;
+ vcpu->arch.pause = false;
+ smp_mb(); /* Make sure the above is visible */
+
+ wake_up_interruptible(wq);
+
+ return KVM_PSCI_RET_SUCCESS;
+}
+
+/**
+ * kvm_psci_call - handle PSCI call if r0 value is in range
+ * @vcpu: Pointer to the VCPU struct
+ *
+ * Handle PSCI calls from guests through traps from HVC or SMC instructions.
+ * The calling convention is similar to SMC calls to the secure world where
+ * the function number is placed in r0 and this function returns true if the
+ * function number specified in r0 is withing the PSCI range, and false
+ * otherwise.
+ */
+bool kvm_psci_call(struct kvm_vcpu *vcpu)
+{
+ unsigned long psci_fn = *vcpu_reg(vcpu, 0) & ~((u32) 0);
+ unsigned long val;
+
+ switch (psci_fn) {
+ case KVM_PSCI_FN_CPU_OFF:
+ kvm_psci_vcpu_off(vcpu);
+ val = KVM_PSCI_RET_SUCCESS;
+ break;
+ case KVM_PSCI_FN_CPU_ON:
+ val = kvm_psci_vcpu_on(vcpu);
+ break;
+ case KVM_PSCI_FN_CPU_SUSPEND:
+ case KVM_PSCI_FN_MIGRATE:
+ val = KVM_PSCI_RET_NI;
+ break;
+
+ default:
+ return false;
+ }
+
+ *vcpu_reg(vcpu, 0) = val;
+ return true;
+}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index dc63665..500acda 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -636,6 +636,7 @@ struct kvm_ppc_smmu_info {
#define KVM_CAP_IRQFD_RESAMPLE 82
#define KVM_CAP_PPC_BOOKE_WATCHDOG 83
#define KVM_CAP_PPC_HTAB_FD 84
+#define KVM_CAP_ARM_PSCI 86

#ifdef KVM_CAP_IRQ_ROUTING