Thread (23 messages) 23 messages, 3 authors, 2021-11-30

Re: [RFC PATCH v2 03/11] KVM: Introduce kvm_vm_has_run_once

From: Marc Zyngier <maz@kernel.org>
Date: 2021-11-22 16:31:52
Also in: kvmarm, linux-arm-kernel, lkml

On Sat, 13 Nov 2021 01:22:26 +0000,
Raghavendra Rao Ananta [off-list ref] wrote:
quoted hunk ↗ jump to hunk
The upcoming patches need a way to detect if the VM, as
a whole, has started. Hence, unionize kvm_vcpu_has_run_once()
of all the vcpus of the VM and build kvm_vm_has_run_once()
to achieve the functionality.

No functional change intended.

Signed-off-by: Raghavendra Rao Ananta <redacted>
---
 include/linux/kvm_host.h |  2 ++
 virt/kvm/kvm_main.c      | 17 +++++++++++++++++
 2 files changed, 19 insertions(+)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index b373929c71eb..102e00c0e21c 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1854,4 +1854,6 @@ static inline bool kvm_vcpu_has_run_once(struct kvm_vcpu *vcpu)
 	return vcpu->has_run_once;
 }
 
+bool kvm_vm_has_run_once(struct kvm *kvm);
+
 #endif
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 1ec8a8e959b2..3d8d96e8f61d 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4339,6 +4339,23 @@ static int kvm_vm_ioctl_get_stats_fd(struct kvm *kvm)
 	return fd;
 }
 
+bool kvm_vm_has_run_once(struct kvm *kvm)
+{
+	int i, ret = false;
+	struct kvm_vcpu *vcpu;
+
+	mutex_lock(&kvm->lock);
+
+	kvm_for_each_vcpu(i, vcpu, kvm) {
+		ret = kvm_vcpu_has_run_once(vcpu);
+		if (ret)
+			break;
+	}
+
+	mutex_unlock(&kvm->lock);
+	return ret;
+}
This is horribly racy. Nothing prevents a vcpu from running behind
your back. If you want any sort of guarantee, look at what we do in
kvm_vgic_create(). Alexandru has patches that extract it to make it
generally available (at least for arm64).

	M.

-- 
Without deviation from the norm, progress is not possible.
Keyboard shortcuts
hback out one level
jnext message in thread
kprevious message in thread
ldrill in
Escclose help / fold thread tree
?toggle this help