[PATCH 1/2] KVM: VMX: Notify if VMX is already in use

[Sasha Levin]

Currently we silently fail if VMX is already in use by a different
virtualization technology.

This is bad since it's non-obvious for the user, and its not too uncommon
for users to have several of these installed on same host.

This patch adds a message to notify the user of the problem.

Cc: Joerg Roedel <joerg.roedel@xxxxxxx>
Cc: Avi Kivity <avi@xxxxxxxxxx>
Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Cc: kvm@xxxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <levinsasha928@xxxxxxxxx>
---
 arch/x86/kvm/vmx.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 4ceced2..0ef59ed 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2300,8 +2300,11 @@ static int hardware_enable(void *garbage)
 	u64 phys_addr = __pa(per_cpu(vmxarea, cpu));
 	u64 old, test_bits;
 
-	if (read_cr4() & X86_CR4_VMXE)
+	if (read_cr4() & X86_CR4_VMXE) {
+		printk(KERN_ERR "hardware_enable: VMX already in use on CPU%d. "
+				"Are you already another hypervisor?\n", cpu);
 		return -EBUSY;
+	}
 
 	INIT_LIST_HEAD(&per_cpu(loaded_vmcss_on_cpu, cpu));
 	rdmsrl(MSR_IA32_FEATURE_CONTROL, old);
-- 
1.7.8.rc4

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