[PATCH] x86, add hypervisor name to dump_stack()

[PATCH] x86, add hypervisor name to dump_stack()

[Prarit Bhargava]

Debugging crash, panics, stack trace WARN_ONs, etc., from both virtual and
bare-metal boots can get difficult very quickly.  While there are ways to
decipher the output and determine if the output is from a virtual guest,
the in-kernel hypervisors now have a single registration point and set
x86_hyper.  We can use this to output a single extra line on virtual
machines that indicates the hypervisor type.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Marcelo Tostatti <mtosatti@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: kvm@vger.kernel.org
Cc: x86@kernel.org
---
 arch/x86/kernel/dumpstack.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index ae42418b..75a635e 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -17,6 +17,7 @@
 #include <linux/sysfs.h>
 
 #include <asm/stacktrace.h>
+#include <asm/hypervisor.h>
 
 
 int panic_on_unrecovered_nmi;
@@ -193,6 +194,8 @@ void dump_stack(void)
 		init_utsname()->release,
 		(int)strcspn(init_utsname()->version, " "),
 		init_utsname()->version);
+	if (x86_hyper && x86_hyper->name)
+		printk("Hypervisor: %s\n",  x86_hyper->name);
 	show_trace(NULL, NULL, &stack, bp);
 }
 EXPORT_SYMBOL(dump_stack);
-- 
1.7.9.3

Re: [PATCH] x86, add hypervisor name to dump_stack()

[Ingo Molnar]

* Prarit Bhargava <prarit@redhat.com> wrote:

> Debugging crash, panics, stack trace WARN_ONs, etc., from both virtual and
> bare-metal boots can get difficult very quickly.  While there are ways to
> decipher the output and determine if the output is from a virtual guest,
> the in-kernel hypervisors now have a single registration point and set
> x86_hyper.  We can use this to output a single extra line on virtual
> machines that indicates the hypervisor type.
> 
> Signed-off-by: Prarit Bhargava <prarit@redhat.com>
> Cc: Avi Kivity <avi@redhat.com>
> Cc: Gleb Natapov <gleb@redhat.com>
> Cc: Alex Williamson <alex.williamson@redhat.com>
> Cc: Marcelo Tostatti <mtosatti@redhat.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: kvm@vger.kernel.org
> Cc: x86@kernel.org
> ---
>  arch/x86/kernel/dumpstack.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
> index ae42418b..75a635e 100644
> --- a/arch/x86/kernel/dumpstack.c
> +++ b/arch/x86/kernel/dumpstack.c
> @@ -17,6 +17,7 @@
>  #include <linux/sysfs.h>
>  
>  #include <asm/stacktrace.h>
> +#include <asm/hypervisor.h>
>  
>  
>  int panic_on_unrecovered_nmi;
> @@ -193,6 +194,8 @@ void dump_stack(void)
>  		init_utsname()->release,
>  		(int)strcspn(init_utsname()->version, " "),
>  		init_utsname()->version);
> +	if (x86_hyper && x86_hyper->name)
> +		printk("Hypervisor: %s\n",  x86_hyper->name);
>  	show_trace(NULL, NULL, &stack, bp);

Looks useful, but please don't waste a full new line on it but 
embedd it in the already existing status line that prints 
details like release and version.

Thanks,

	Ingo

Re: [PATCH] x86, add hypervisor name to dump_stack()

[Prarit Bhargava]

On 10/24/2012 05:49 AM, Ingo Molnar wrote:
> 
> * Prarit Bhargava <prarit@redhat.com> wrote:
> 
>> Debugging crash, panics, stack trace WARN_ONs, etc., from both virtual and
>> bare-metal boots can get difficult very quickly.  While there are ways to
>> decipher the output and determine if the output is from a virtual guest,
>> the in-kernel hypervisors now have a single registration point and set
>> x86_hyper.  We can use this to output a single extra line on virtual
>> machines that indicates the hypervisor type.
>>
>> Signed-off-by: Prarit Bhargava <prarit@redhat.com>
>> Cc: Avi Kivity <avi@redhat.com>
>> Cc: Gleb Natapov <gleb@redhat.com>
>> Cc: Alex Williamson <alex.williamson@redhat.com>
>> Cc: Marcelo Tostatti <mtosatti@redhat.com>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: kvm@vger.kernel.org
>> Cc: x86@kernel.org
>> ---
>>  arch/x86/kernel/dumpstack.c |    3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
>> index ae42418b..75a635e 100644
>> --- a/arch/x86/kernel/dumpstack.c
>> +++ b/arch/x86/kernel/dumpstack.c
>> @@ -17,6 +17,7 @@
>>  #include <linux/sysfs.h>
>>  
>>  #include <asm/stacktrace.h>
>> +#include <asm/hypervisor.h>
>>  
>>  
>>  int panic_on_unrecovered_nmi;
>> @@ -193,6 +194,8 @@ void dump_stack(void)
>>  		init_utsname()->release,
>>  		(int)strcspn(init_utsname()->version, " "),
>>  		init_utsname()->version);
>> +	if (x86_hyper && x86_hyper->name)
>> +		printk("Hypervisor: %s\n",  x86_hyper->name);
>>  	show_trace(NULL, NULL, &stack, bp);
> 
> Looks useful, but please don't waste a full new line on it but 
> embedd it in the already existing status line that prints 
> details like release and version.

Ingo, I thought about doing that but since x86_hyper can be NULL (... maybe it
should initialized to "Bare-metal" or "No Hypervisor"?) I didn't want to break
up the printk line.  I'll look into doing it a different way...

P.

> 
> Thanks,
> 
> 	Ingo

Re: [PATCH] x86, add hypervisor name to dump_stack()

[Ingo Molnar]

* Prarit Bhargava <prarit@redhat.com> wrote:

> > Looks useful, but please don't waste a full new line on it 
> > but embedd it in the already existing status line that 
> > prints details like release and version.
> 
> Ingo, I thought about doing that but since x86_hyper can be 
> NULL (... maybe it should initialized to "Bare-metal" or "No 
> Hypervisor"?) I didn't want to break up the printk line.  I'll 
> look into doing it a different way...

You don't have to break it up - just initialize a name string 
to:

	const char *machine_name = "x86";
	const char *kernel_type = "native";

	if (x86_hyperv) {
		machine_name = x86_hyperv->name;
		kernel_type = "guest";
	}

And print it as:

          "[%s %s kernel]", machine_name, kernel_type

That way we'll get nice:

    ... [x86 native kernel]
    ... [KVM guest kernel]
    ... [Xen guest kernel]
    etc.

Printouts. Please use the naming I outlined above, that's how we 
refer to these kernels within arch/x86/.

(The above code is pseudocode, untested.)

Thanks,

	Ingo