[PATCH 2/2] kvm: arm/arm64: implement kvm_arm_[halt, resume]_guest

Hi Chistoffer,
On 07/18/2015 11:18 AM, Christoffer Dall wrote:

On Mon, Jul 06, 2015 at 02:49:56PM +0200, Eric Auger wrote:

quoted

On halt, the guest is forced to exit and prevented from being
re-entered. This is synchronous.

Those two operations will be needed for IRQ forwarding setting.

Signed-off-by: Eric Auger <redacted>

---
RFC v1 -> v2:
- add __maybe_unused

RFC:
- rename the function and this latter becomes static
- remove __KVM_HAVE_ARCH_HALT_GUEST

v4 -> v5: add arm64 support
- also defines __KVM_HAVE_ARCH_HALT_GUEST for arm64
- add pause field
---
 arch/arm/include/asm/kvm_host.h   |  3 +++
 arch/arm/kvm/arm.c                | 35 ++++++++++++++++++++++++++++++++---
 arch/arm64/include/asm/kvm_host.h |  3 +++
 3 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 304004d..899ae27 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h

@@ -132,6 +132,9 @@ struct kvm_vcpu_arch {
 	/* vcpu power-off state */
 	bool power_off;
 
+	/* Don't run the guest */
+	bool pause;
+
 	/* IO related fields */
 	struct kvm_decode mmio_decode;
 

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 7537e68..46d4ef6 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c

@@ -471,11 +471,39 @@ bool kvm_arch_intc_initialized(struct kvm *kvm)
 	return vgic_initialized(kvm);
 }
 
+static void kvm_arm_halt_guest(struct kvm *kvm) __maybe_unused;
+static void kvm_arm_resume_guest(struct kvm *kvm) __maybe_unused;
+
+static void kvm_arm_halt_guest(struct kvm *kvm)
+{
+	int i;
+	struct kvm_vcpu *vcpu;
+
+	kvm_for_each_vcpu(i, vcpu, kvm)
+		vcpu->arch.pause = true;
+	force_vm_exit(cpu_all_mask);
+}
+
+static void kvm_arm_resume_guest(struct kvm *kvm)
+{
+	int i;
+	struct kvm_vcpu *vcpu;
+
+	kvm_for_each_vcpu(i, vcpu, kvm) {
+		wait_queue_head_t *wq = kvm_arch_vcpu_wq(vcpu);
+
+		vcpu->arch.pause = false;
+		wake_up_interruptible(wq);
+	}
+}
+
+
 static void vcpu_pause(struct kvm_vcpu *vcpu)
 {
 	wait_queue_head_t *wq = kvm_arch_vcpu_wq(vcpu);
 
-	wait_event_interruptible(*wq, !vcpu->arch.power_off);
+	wait_event_interruptible(*wq, ((!vcpu->arch.power_off) &&
+				       (!vcpu->arch.pause)));
 }
 
 static int kvm_vcpu_initialized(struct kvm_vcpu *vcpu)

@@ -525,7 +553,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
 
 		update_vttbr(vcpu->kvm);
 
-		if (vcpu->arch.power_off)
+		if (vcpu->arch.power_off || vcpu->arch.pause)
 			vcpu_pause(vcpu);

These two changes really make me feel like kvm_arch_vcpu_runnable()
should be changed to check for both flags and all thes eplaces should
check for runnable instead.

To make the runnable function more robust, perhaps it should check:

1. The vcpu is neither paused nor powered off
2. The vcpu is not in a WFI state (vcpu->arch.wfi_request) OR there are
   pending interrupts (the current check).

I did not understand what you meant by this vcpu->arch.wfi_request,
which I could not find. In case we call runnable from
kvm_vcpu_block/kvm_vcpu_check_block we sometimes are in WFI
(kvm_handle_wfx)?

Thanks

Eric

Then the logic would fit the name of the function, instead of being a
specific check only called through handle_wfx.

quoted

 
 		/*

@@ -551,7 +579,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
 			run->exit_reason = KVM_EXIT_INTR;
 		}
 
-		if (ret <= 0 || need_new_vmid_gen(vcpu->kvm)) {
+		if (ret <= 0 || need_new_vmid_gen(vcpu->kvm) ||
+		    vcpu->arch.pause) {

so why do we need to re-check the pause flag, but not the power_off
flag?  That is non-trivial for sure, so if it's correct, deserves a
comment.  Also see my comment on the last patch.

quoted

 			local_irq_enable();
 			preempt_enable();
 			kvm_vgic_sync_hwstate(vcpu);

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 009da6b..69e3785 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h

@@ -125,6 +125,9 @@ struct kvm_vcpu_arch {
 	/* vcpu power-off state */
 	bool power_off;
 
+	/* Don't run the guest */

Probably need to be more clear about this being an implementation
requirement rather than being guest visible or related to any
architectural concept.

quoted

+	bool pause;
+
 	/* IO related fields */
 	struct kvm_decode mmio_decode;
 
-- 
1.9.1

Thanks,
-Christoffer