linux-kernel - [PATCH 2/4] KVM: x86: Ensure all logical CPUs have consistent reserved cr4 bits

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Message-Id: <20191210224416.10757-3-sean.j.christopherson@intel.com>
Date:   Tue, 10 Dec 2019 14:44:14 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jun Nakajima <jun.nakajima@...el.com>
Subject: [PATCH 2/4] KVM: x86: Ensure all logical CPUs have consistent reserved cr4 bits

Check the current CPU's reserved cr4 bits against the mask calculated
for the boot CPU to ensure consistent behavior across all CPUs.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---

I'm on the fence as to whether this is gratuitous or useful, which is
why it's a separate patch and not tagged for stable.

 arch/x86/kvm/x86.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 321eecb4cffd..ab3a4104febf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9415,6 +9415,13 @@ void kvm_arch_hardware_unsetup(void)
 
 int kvm_arch_check_processor_compat(void)
 {
+	struct cpuinfo_x86 *c = &cpu_data(smp_processor_id());
+
+	WARN_ON(!irqs_disabled());
+
+	if (kvm_host_cr4_reserved_bits(c) != cr4_reserved_bits)
+		return -EIO;
+
 	return kvm_x86_ops->check_processor_compatibility();
 }
 
-- 
2.24.0