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); + #endifdiff --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.