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

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Message-Id: <5dc935a4f03af56a38128701847935afe676307c.1660974107.git.isaku.yamahata@intel.com>
Date:   Fri, 19 Aug 2022 23:00:24 -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 18/18] KVM: 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>
---
 virt/kvm/kvm_arch.c | 16 ++--------------
 1 file changed, 2 insertions(+), 14 deletions(-)

diff --git a/virt/kvm/kvm_arch.c b/virt/kvm/kvm_arch.c
index 94dd57bbc8bd..03946321a21c 100644
--- a/virt/kvm/kvm_arch.c
+++ b/virt/kvm/kvm_arch.c
@@ -12,22 +12,16 @@
 
 #include <linux/kvm_host.h>
 
-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 = kvm_arch_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;
 }
 
@@ -41,13 +35,7 @@ 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);
 	kvm_arch_hardware_disable();
 }
 
-- 
2.25.1