linux-kernel - [PATCH v5 14/30] KVM: Add arch hook for cpu online event

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Message-Id: <ae4b7178d1f6c95bcf0895f27d8939af514a1af2.1663869838.git.isaku.yamahata@intel.com>
Date:   Thu, 22 Sep 2022 11:20:43 -0700
From:   isaku.yamahata@...el.com
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>
Cc:     isaku.yamahata@...el.com, isaku.yamahata@...il.com,
        Kai Huang <kai.huang@...el.com>, Chao Gao <chao.gao@...el.com>,
        Atish Patra <atishp@...shpatra.org>,
        Shaokun Zhang <zhangshaokun@...ilicon.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Huang Ying <ying.huang@...el.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>
Subject: [PATCH v5 14/30] KVM: Add arch hook for cpu online event

From: Isaku Yamahata <isaku.yamahata@...el.com>

Factor out the logic on cpu hotplug event as arch callback.  Later kvm/x86
will override it.

Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
---
 include/linux/kvm_host.h |  1 +
 virt/kvm/kvm_main.c      | 58 +++++++++++++++++++++++-----------------
 2 files changed, 34 insertions(+), 25 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 1adbf74e3047..013b33a19030 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1434,6 +1434,7 @@ void kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu, struct dentry *debugfs_
 static inline void kvm_create_vcpu_debugfs(struct kvm_vcpu *vcpu) {}
 #endif
 
+int kvm_arch_online_cpu(unsigned int cpu, int usage_count);
 int kvm_arch_reboot(int val);
 int kvm_arch_suspend(int usage_count);
 void kvm_arch_resume(int usage_count);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 1270f88c2a1e..4c535ae412a7 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1142,6 +1142,38 @@ int __weak kvm_arch_del_vm(int usage_count)
 	return 0;
 }
 
+int __weak kvm_arch_online_cpu(unsigned int cpu, int usage_count)
+{
+	int ret = 0;
+
+	ret = kvm_arch_check_processor_compat();
+	if (ret)
+		return ret;
+
+	/*
+	 * Abort the CPU online process if hardware virtualization cannot
+	 * be enabled. Otherwise running VMs would encounter unrecoverable
+	 * errors when scheduled to this CPU.
+	 */
+	if (usage_count) {
+		WARN_ON_ONCE(atomic_read(&hardware_enable_failed));
+
+		/*
+		 * arch callback kvm_arch_hardware_eanble() assumes that
+		 * preemption is disabled for historical reason.  Disable
+		 * preemption until all arch callbacks are fixed.
+		 */
+		preempt_disable();
+		hardware_enable_nolock(NULL);
+		preempt_enable();
+		if (atomic_read(&hardware_enable_failed)) {
+			atomic_set(&hardware_enable_failed, 0);
+			ret = -EIO;
+		}
+	}
+	return ret;
+}
+
 int __weak kvm_arch_reboot(int val)
 {
 	on_each_cpu(hardware_disable_nolock, NULL, 1);
@@ -5085,32 +5117,8 @@ static int kvm_online_cpu(unsigned int cpu)
 {
 	int ret;
 
-	ret = kvm_arch_check_processor_compat();
-	if (ret)
-		return ret;
-
 	mutex_lock(&kvm_lock);
-	/*
-	 * Abort the CPU online process if hardware virtualization cannot
-	 * be enabled. Otherwise running VMs would encounter unrecoverable
-	 * errors when scheduled to this CPU.
-	 */
-	if (kvm_usage_count) {
-		WARN_ON_ONCE(atomic_read(&hardware_enable_failed));
-
-		/*
-		 * arch callback kvm_arch_hardware_eanble() assumes that
-		 * preemption is disabled for historical reason.  Disable
-		 * preemption until all arch callbacks are fixed.
-		 */
-		preempt_disable();
-		hardware_enable_nolock(NULL);
-		preempt_enable();
-		if (atomic_read(&hardware_enable_failed)) {
-			atomic_set(&hardware_enable_failed, 0);
-			ret = -EIO;
-		}
-	}
+	ret = kvm_arch_online_cpu(cpu, kvm_usage_count);
 	mutex_unlock(&kvm_lock);
 	return ret;
 }
-- 
2.25.1