[PATCH v2 1/2] KVM: VMX: Notify if VMX is already in use

[PATCH v2 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.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
 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_once(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

[PATCH v2 2/2] KVM: SVM: Notify if SVM is already in use

[Sasha Levin]

Currently we silently fail if SVM 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.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
 arch/x86/kvm/svm.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index e32243e..8d1a066 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -587,8 +587,11 @@ static int svm_hardware_enable(void *garbage)
 	int me = raw_smp_processor_id();
 
 	rdmsrl(MSR_EFER, efer);
-	if (efer & EFER_SVME)
+	if (efer & EFER_SVME) {
+		printk_once(KERN_ERR "svm_hardware_enable: SVM already in use on CPU%d. "
+				"Are you already another hypervisor?\n", me);
 		return -EBUSY;
+	}
 
 	if (!has_svm()) {
 		printk(KERN_ERR "svm_hardware_enable: err EOPNOTSUPP on %d\n",
-- 
1.7.8

Re: [PATCH v2 1/2] KVM: VMX: Notify if VMX is already in use

[Andreas Färber]

Am 07.12.2011 15:34, schrieb 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.

Being more verbose is a good move.

> Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
> ---
>  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_once(KERN_ERR "hardware_enable: VMX already in use on CPU%d. "
> +				"Are you already another hypervisor?\n", cpu);

Since this question addresses the user, it should read:
"Are you already using another hypervisor?\n" (or the like)

Applies to 2/2 as well.

Andreas

>  		return -EBUSY;
> +	}
>  
>  	INIT_LIST_HEAD(&per_cpu(loaded_vmcss_on_cpu, cpu));
>  	rdmsrl(MSR_IA32_FEATURE_CONTROL, old);


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