[PATCH v2] xen: Make VPMU init message look less scary

[PATCH v2] xen: Make VPMU init message look less scary

[Juergen Gross]

The default for the Xen hypervisor is to not enable VPMU in order to
avoid security issues. In this case the Linux kernel will issue the
message "Could not initialize VPMU for cpu 0, error -95" which looks
more like an error than a normal state.

Change the message to something less scary in case the hypervisor
returns EOPNOTSUPP when trying to activate VPMU.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V2: modify error message as suggested by Konrad Wilk
---
 arch/x86/xen/pmu.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/xen/pmu.c b/arch/x86/xen/pmu.c
index 32bdc2c..bfe8880 100644
--- a/arch/x86/xen/pmu.c
+++ b/arch/x86/xen/pmu.c
@@ -547,8 +547,11 @@ void xen_pmu_init(int cpu)
 	return;
 
 fail:
-	pr_info_once("Could not initialize VPMU for cpu %d, error %d\n",
-		cpu, err);
+	if (err == -EOPNOTSUPP)
+		pr_info_once("VPMU disabled by hypervisor.\n");
+	else
+		pr_info_once("Could not initialize VPMU for cpu %d, error %d\n",
+			cpu, err);
 	free_pages((unsigned long)xenpmu_data, 0);
 }
 
-- 
2.6.6

Re: [Xen-devel] [PATCH v2] xen: Make VPMU init message look less scary

[Jan Beulich]

>>> On 02.08.16 at 08:43, <JGross@suse.com> wrote:
> --- a/arch/x86/xen/pmu.c
> +++ b/arch/x86/xen/pmu.c
> @@ -547,8 +547,11 @@ void xen_pmu_init(int cpu)
>  	return;
>  
>  fail:
> -	pr_info_once("Could not initialize VPMU for cpu %d, error %d\n",
> -		cpu, err);
> +	if (err == -EOPNOTSUPP)
> +		pr_info_once("VPMU disabled by hypervisor.\n");
> +	else
> +		pr_info_once("Could not initialize VPMU for cpu %d, error %d\n",
> +			cpu, err);

I'm sorry for not already having thought about this for v1, but
what about older hypervisors, where the hypercall would return
-ENOSYS?

Jan

Re: [Xen-devel] [PATCH v2] xen: Make VPMU init message look less scary

[Juergen Gross]

On 02/08/16 09:10, Jan Beulich wrote:
>>>> On 02.08.16 at 08:43, <JGross@suse.com> wrote:
>> --- a/arch/x86/xen/pmu.c
>> +++ b/arch/x86/xen/pmu.c
>> @@ -547,8 +547,11 @@ void xen_pmu_init(int cpu)
>>  	return;
>>  
>>  fail:
>> -	pr_info_once("Could not initialize VPMU for cpu %d, error %d\n",
>> -		cpu, err);
>> +	if (err == -EOPNOTSUPP)
>> +		pr_info_once("VPMU disabled by hypervisor.\n");
>> +	else
>> +		pr_info_once("Could not initialize VPMU for cpu %d, error %d\n",
>> +			cpu, err);
> 
> I'm sorry for not already having thought about this for v1, but
> what about older hypervisors, where the hypercall would return
> -ENOSYS?

I wasn't aware of that possibility. It should be covered, of course!

V3 will be sent soon...

Thanks for noticing now,


Juergen