linux-kernel - [RFC PATCH v3 01/11] KVM: Capture VM start

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Date:   Tue,  4 Jan 2022 19:49:08 +0000
From:   Raghavendra Rao Ananta <rananta@...gle.com>
To:     Marc Zyngier <maz@...nel.org>, Andrew Jones <drjones@...hat.com>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Peter Shier <pshier@...gle.com>,
        Ricardo Koller <ricarkol@...gle.com>,
        Oliver Upton <oupton@...gle.com>,
        Reiji Watanabe <reijiw@...gle.com>,
        Jing Zhang <jingzhangos@...gle.com>,
        Raghavendra Rao Anata <rananta@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: [RFC PATCH v3 01/11] KVM: Capture VM start

Capture the start of the KVM VM, which is basically the
start of any vCPU run. This state of the VM is helpful
in the upcoming patches to prevent user-space from
configuring certain VM features after the VM has started
running.

Signed-off-by: Raghavendra Rao Ananta <rananta@...gle.com>
---
 include/linux/kvm_host.h | 3 +++
 virt/kvm/kvm_main.c      | 9 +++++++++
 2 files changed, 12 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index c310648cc8f1..d0bd8f7a026c 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -623,6 +623,7 @@ struct kvm {
 	struct notifier_block pm_notifier;
 #endif
 	char stats_id[KVM_STATS_NAME_SIZE];
+	bool vm_started;
 };
 
 #define kvm_err(fmt, ...) \
@@ -1666,6 +1667,8 @@ static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu)
 	}
 }
 
+#define kvm_vm_has_started(kvm) (kvm->vm_started)
+
 extern bool kvm_rebooting;
 
 extern unsigned int halt_poll_ns;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 72c4e6b39389..962b91ac2064 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3686,6 +3686,7 @@ static long kvm_vcpu_ioctl(struct file *filp,
 	int r;
 	struct kvm_fpu *fpu = NULL;
 	struct kvm_sregs *kvm_sregs = NULL;
+	struct kvm *kvm = vcpu->kvm;
 
 	if (vcpu->kvm->mm != current->mm || vcpu->kvm->vm_dead)
 		return -EIO;
@@ -3723,6 +3724,14 @@ static long kvm_vcpu_ioctl(struct file *filp,
 			if (oldpid)
 				synchronize_rcu();
 			put_pid(oldpid);
+
+			/*
+			 * Since we land here even on the first vCPU run,
+			 * we can mark that the VM has started running.
+			 */
+			mutex_lock(&kvm->lock);
+			kvm->vm_started = true;
+			mutex_unlock(&kvm->lock);
 		}
 		r = kvm_arch_vcpu_ioctl_run(vcpu);
 		trace_kvm_userspace_exit(vcpu->run->exit_reason, r);
-- 
2.34.1.448.ga2b2bfdf31-goog