[RFC PATCH 2/5] KVM: arm64: Move WFI execution to check_vcpu_requests()
Jean-Philippe Brucker
jean-philippe at linaro.org
Tue Jun 8 08:48:03 PDT 2021
Prepare for WFI requests from userspace, by adding a suspend request and
moving the WFI execution into check_vcpu_requests(), next to the
power-off logic.
vcpu->arch.mp_state, previously only RUNNABLE or STOPPED, supports an
additional state HALTED and two new state transitions:
RUNNABLE -> HALTED from WFI or PSCI CPU_SUSPEND (same vCPU)
HALTED -> RUNNABLE vGIC IRQ, pending timer, signal
There shouldn't be any functional change with this patch, even though
the KVM_GET_MP_STATE ioctl could now in theory return
KVM_MP_STATE_HALTED, which would break some users' mp_state support. In
practice it should not happen because we do not return to userspace with
HALTED state. Both WFI and PSCI CPU_SUSPEND stay in the vCPU run loop
until the suspend request is consumed. It does feel fragile though,
maybe we should explicitly return RUNNABLE in KVM_GET_MP_STATE in place
of HALTED, to prevent future breakage.
Signed-off-by: Jean-Philippe Brucker <jean-philippe at linaro.org>
---
arch/arm64/include/asm/kvm_host.h | 2 ++
arch/arm64/kvm/arm.c | 18 ++++++++++++++-
arch/arm64/kvm/handle_exit.c | 3 +--
arch/arm64/kvm/psci.c | 37 +++++++++++++------------------
4 files changed, 35 insertions(+), 25 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 55a04f4d5919..3ca732feb9a5 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -46,6 +46,7 @@
#define KVM_REQ_VCPU_RESET KVM_ARCH_REQ(2)
#define KVM_REQ_RECORD_STEAL KVM_ARCH_REQ(3)
#define KVM_REQ_RELOAD_GICv4 KVM_ARCH_REQ(4)
+#define KVM_REQ_SUSPEND KVM_ARCH_REQ(5)
#define KVM_DIRTY_LOG_MANUAL_CAPS (KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE | \
KVM_DIRTY_LOG_INITIALLY_SET)
@@ -722,6 +723,7 @@ int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
struct kvm_device_attr *attr);
void kvm_arm_vcpu_power_off(struct kvm_vcpu *vcpu);
bool kvm_arm_vcpu_is_off(struct kvm_vcpu *vcpu);
+void kvm_arm_vcpu_suspend(struct kvm_vcpu *vcpu);
/* Guest/host FPSIMD coordination helpers */
int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu);
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index bcc24adb9c0a..d8cbaa0373c7 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -447,6 +447,12 @@ bool kvm_arm_vcpu_is_off(struct kvm_vcpu *vcpu)
return vcpu->arch.mp_state == KVM_MP_STATE_STOPPED;
}
+void kvm_arm_vcpu_suspend(struct kvm_vcpu *vcpu)
+{
+ vcpu->arch.mp_state = KVM_MP_STATE_HALTED;
+ kvm_make_request(KVM_REQ_SUSPEND, vcpu);
+}
+
int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
struct kvm_mp_state *mp_state)
{
@@ -667,6 +673,8 @@ static int kvm_vcpu_initialized(struct kvm_vcpu *vcpu)
static void check_vcpu_requests(struct kvm_vcpu *vcpu)
{
+ bool irq_pending;
+
if (kvm_request_pending(vcpu)) {
if (kvm_check_request(KVM_REQ_SLEEP, vcpu))
vcpu_req_sleep(vcpu);
@@ -678,7 +686,7 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu)
* Clear IRQ_PENDING requests that were made to guarantee
* that a VCPU sees new virtual interrupts.
*/
- kvm_check_request(KVM_REQ_IRQ_PENDING, vcpu);
+ irq_pending = kvm_check_request(KVM_REQ_IRQ_PENDING, vcpu);
if (kvm_check_request(KVM_REQ_RECORD_STEAL, vcpu))
kvm_update_stolen_time(vcpu);
@@ -690,6 +698,14 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu)
vgic_v4_load(vcpu);
preempt_enable();
}
+
+ if (kvm_check_request(KVM_REQ_SUSPEND, vcpu)) {
+ if (!irq_pending) {
+ kvm_vcpu_block(vcpu);
+ kvm_clear_request(KVM_REQ_UNHALT, vcpu);
+ }
+ vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
+ }
}
}
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 6f48336b1d86..9717df3104cf 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -95,8 +95,7 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu)
} else {
trace_kvm_wfx_arm64(*vcpu_pc(vcpu), false);
vcpu->stat.wfi_exit_stat++;
- kvm_vcpu_block(vcpu);
- kvm_clear_request(KVM_REQ_UNHALT, vcpu);
+ kvm_arm_vcpu_suspend(vcpu);
}
kvm_incr_pc(vcpu);
diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
index 24b4a2265dbd..42a307ceb95f 100644
--- a/arch/arm64/kvm/psci.c
+++ b/arch/arm64/kvm/psci.c
@@ -31,27 +31,6 @@ static unsigned long psci_affinity_mask(unsigned long affinity_level)
return 0;
}
-static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu)
-{
- /*
- * NOTE: For simplicity, we make VCPU suspend emulation to be
- * same-as WFI (Wait-for-interrupt) emulation.
- *
- * This means for KVM the wakeup events are interrupts and
- * this is consistent with intended use of StateID as described
- * in section 5.4.1 of PSCI v0.2 specification (ARM DEN 0022A).
- *
- * Further, we also treat power-down request to be same as
- * stand-by request as-per section 5.4.2 clause 3 of PSCI v0.2
- * specification (ARM DEN 0022A). This means all suspend states
- * for KVM will preserve the register state.
- */
- kvm_vcpu_block(vcpu);
- kvm_clear_request(KVM_REQ_UNHALT, vcpu);
-
- return PSCI_RET_SUCCESS;
-}
-
static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
{
struct vcpu_reset_state *reset_state;
@@ -227,7 +206,21 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
break;
case PSCI_0_2_FN_CPU_SUSPEND:
case PSCI_0_2_FN64_CPU_SUSPEND:
- val = kvm_psci_vcpu_suspend(vcpu);
+ /*
+ * NOTE: For simplicity, we make VCPU suspend emulation to be
+ * same-as WFI (Wait-for-interrupt) emulation.
+ *
+ * This means for KVM the wakeup events are interrupts and this
+ * is consistent with intended use of StateID as described in
+ * section 5.4.1 of PSCI v0.2 specification (ARM DEN 0022A).
+ *
+ * Further, we also treat power-down request to be same as
+ * stand-by request as-per section 5.4.2 clause 3 of PSCI v0.2
+ * specification (ARM DEN 0022A). This means all suspend states
+ * for KVM will preserve the register state.
+ */
+ kvm_arm_vcpu_suspend(vcpu);
+ val = PSCI_RET_SUCCESS;
break;
case PSCI_0_2_FN_CPU_OFF:
kvm_arm_vcpu_power_off(vcpu);
--
2.31.1
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