[PATCH v3] xen: Make VPMU init message look less scary

[PATCH v3] 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 or ENOSYS when trying to activate VPMU.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V3: support older hypervisors returning ENOSYS as requested by
    Jan Beulich
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..b9fc525 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 || err == -ENOSYS)
+		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: [PATCH v3] xen: Make VPMU init message look less scary

[Juergen Gross]

On 02/08/16 09:22, Juergen Gross wrote:
> 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 or ENOSYS when trying to activate VPMU.
> 
> Signed-off-by: Juergen Gross <jgross@suse.com>

David, could you take this patch, please?


Juergen

Re: [Xen-devel] [PATCH v3] xen: Make VPMU init message look less scary

[David Vrabel]

On 02/08/16 08:22, Juergen Gross wrote:
> 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 or ENOSYS when trying to activate VPMU.

Applied to for-linus-4.9, thanks.

David