linux-kernel - [PATCH 5/6] KVM: x86: Remove WARN_ON in kvm_arch_check_processor

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Message-Id: <20211227081515.2088920-6-chao.gao@intel.com>
Date:   Mon, 27 Dec 2021 16:15:11 +0800
From:   Chao Gao <chao.gao@...el.com>
To:     kvm@...r.kernel.org, pbonzini@...hat.com, kevin.tian@...el.com,
        tglx@...utronix.de
Cc:     Chao Gao <chao.gao@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: [PATCH 5/6] KVM: x86: Remove WARN_ON in kvm_arch_check_processor_compat

kvm_arch_check_processor_compat() needn't be called with interrupt
disabled, as it only reads some CRs/MSRs which won't be clobbered
by interrupt handlers or softirq.

What really needed is disabling preemption. No additional check is
added because if CONFIG_DEBUG_PREEMPT is enabled, smp_processor_id()
(right above the WARN_ON()) can help to detect any violation.

Signed-off-by: Chao Gao <chao.gao@...el.com>
---
 arch/x86/kvm/x86.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index aa09c8792134..a80e3b0c11a8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11384,8 +11384,6 @@ int kvm_arch_check_processor_compat(void)
 {
 	struct cpuinfo_x86 *c = &cpu_data(smp_processor_id());
 
-	WARN_ON(!irqs_disabled());
-
 	if (__cr4_reserved_bits(cpu_has, c) !=
 	    __cr4_reserved_bits(cpu_has, &boot_cpu_data))
 		return -EIO;
-- 
2.25.1