linux-kernel - [RFC PATCH 17/18] KVM: x86: Remove cpus_hardware

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Date:   Fri, 19 Aug 2022 23:00:23 -0700
From:   isaku.yamahata@...el.com
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...el.com, isaku.yamahata@...il.com,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Kai Huang <kai.huang@...el.com>, Chao Gao <chao.gao@...el.com>,
        Will Deacon <will@...nel.org>
Subject: [RFC PATCH 17/18] KVM: x86: Remove cpus_hardware_enabled and related sanity check

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

cpus_hardware_enabled mask seems incomplete protection against other kernel
component using CPU virtualization feature.  Because it's obscure and
incomplete, remove the check.

Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
---
 arch/x86/kvm/x86.c | 15 +--------------
 1 file changed, 1 insertion(+), 14 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5aa6d5308ee8..f43caa8919ea 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11830,22 +11830,15 @@ void kvm_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector)
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_deliver_sipi_vector);
 
-static cpumask_t cpus_hardware_enabled = CPU_MASK_NONE;
-
 static int __hardware_enable(void)
 {
-	int cpu = raw_smp_processor_id();
 	int r;
 
 	WARN_ON_ONCE(preemptible());
 
-	if (cpumask_test_cpu(cpu, &cpus_hardware_enabled))
-		return 0;
 	r = static_call(kvm_x86_hardware_enable)();
 	if (r)
-		pr_info("kvm: enabling virtualization on CPU%d failed\n", cpu);
-	else
-		cpumask_set_cpu(cpu, &cpus_hardware_enabled);
+		pr_info("kvm: enabling virtualization on CPU%d failed\n", smp_processor_id());
 	return r;
 }
 
@@ -11859,13 +11852,7 @@ static void hardware_enable(void *arg)
 
 static void hardware_disable(void *junk)
 {
-	int cpu = raw_smp_processor_id();
-
 	WARN_ON_ONCE(preemptible());
-
-	if (!cpumask_test_cpu(cpu, &cpus_hardware_enabled))
-		return;
-	cpumask_clear_cpu(cpu, &cpus_hardware_enabled);
 	static_call(kvm_x86_hardware_disable)();
 	drop_user_return_notifiers();
 }
-- 
2.25.1