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From:   isaku.yamahata@intel.com
To:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>
Cc:     isaku.yamahata@intel.com, isaku.yamahata@gmail.com,
        Kai Huang <kai.huang@intel.com>, Chao Gao <chao.gao@intel.com>,
        Atish Patra <atishp@atishpatra.org>,
        Shaokun Zhang <zhangshaokun@hisilicon.com>,
        Qi Liu <liuqi115@huawei.com>,
        John Garry <john.garry@huawei.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Huang Ying <ying.huang@intel.com>,
        Huacai Chen <chenhuacai@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Borislav Petkov <bp@alien8.de>
Subject: [PATCH v3 22/22] RFC: KVM: Remove cpus_hardware_enabled and related sanity check
Date:   Thu,  1 Sep 2022 19:17:57 -0700
Message-Id: <b4fa9880c9d6001e1fb600c2e182750c28dc1162.1662084396.git.isaku.yamahata@intel.com>
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From: Isaku Yamahata <isaku.yamahata@intel.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@intel.com>
---
 virt/kvm/kvm_arch.c | 15 +--------------
 1 file changed, 1 insertion(+), 14 deletions(-)

diff --git a/virt/kvm/kvm_arch.c b/virt/kvm/kvm_arch.c
index bcd82b75fa17..4142f2cb1922 100644
--- a/virt/kvm/kvm_arch.c
+++ b/virt/kvm/kvm_arch.c
@@ -12,23 +12,16 @@
 
 #include <linux/kvm_host.h>
 
-static cpumask_t cpus_hardware_enabled = CPU_MASK_NONE;
-
 static int __hardware_enable(void *caller_name)
 {
-	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_warn("kvm: enabling virtualization on CPU%d failed during %s()\n",
-			cpu, (const char *)caller_name);
-	else
-		cpumask_set_cpu(cpu, &cpus_hardware_enabled);
+			smp_processor_id(), (const char *)caller_name);
 	return r;
 }
 
@@ -42,13 +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