linux-kernel - Re: [PATCH] x86, add hypervisor name to dump

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Date:	Fri, 26 Oct 2012 16:22:05 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Prarit Bhargava <prarit@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Avi Kivity <avi@...hat.com>,
	Gleb Natapov <gleb@...hat.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	Marcelo Tostatti <mtosatti@...hat.com>,
	Ingo Molnar <mingo@...hat.com>, kvm@...r.kernel.org,
	x86@...nel.org
Subject: Re: [PATCH] x86, add hypervisor name to dump_stack() [v2]


* Prarit Bhargava <prarit@...hat.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 additional debug
> information during a panic/oops/stack trace.
> 
> Signed-off-by: Prarit Bhargava <prarit@...hat.com>
> Cc: Avi Kivity <avi@...hat.com>
> Cc: Gleb Natapov <gleb@...hat.com>
> Cc: Alex Williamson <alex.williamson@...hat.com>
> Cc: Marcelo Tostatti <mtosatti@...hat.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: kvm@...r.kernel.org
> Cc: x86@...nel.org
> 
> [v2]: Modifications suggested by Ingo and added changes for similar output
>       from process.c
> ---
>  arch/x86/kernel/dumpstack.c |   11 ++++++++++-
>  arch/x86/kernel/process.c   |   12 +++++++++++-
>  2 files changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
> index ae42418b..5dd680f 100644
> --- a/arch/x86/kernel/dumpstack.c
> +++ b/arch/x86/kernel/dumpstack.c
> @@ -16,6 +16,7 @@
>  #include <linux/nmi.h>
>  #include <linux/sysfs.h>
>  
> +#include <asm/hypervisor.h>
>  #include <asm/stacktrace.h>
>  
>  
> @@ -186,9 +187,17 @@ void dump_stack(void)
>  {
>  	unsigned long bp;
>  	unsigned long stack;
> +	const char *machine_name = "x86";
> +	const char *kernel_type = "native";
> +
> +	if (x86_hyper) {
> +		machine_name = x86_hyper->name;
> +		kernel_type = "guest";
> +	}
>  
>  	bp = stack_frame(current, NULL);
> -	printk("Pid: %d, comm: %.20s %s %s %.*s\n",
> +	printk("[%s %s kernel] Pid: %d, comm: %.20s %s %s %.*s\n",
> +		machine_name, kernel_type,

I'd put the kernel info at the end of the line.

It's all very exciting I know, because we are working on this 
printout right now and all that - but to users and developers 
the PID/comm output plus the backtrace is far more important.

>  		current->pid, current->comm, print_tainted(),
>  		init_utsname()->release,
>  		(int)strcspn(init_utsname()->version, " "),
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> index b644e1c..14bd064 100644
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -28,6 +28,7 @@
>  #include <asm/fpu-internal.h>
>  #include <asm/debugreg.h>
>  #include <asm/nmi.h>
> +#include <asm/hypervisor.h>
>  
>  /*
>   * per-CPU TSS segments. Threads are completely 'soft' on Linux,
> @@ -124,6 +125,13 @@ void exit_thread(void)
>  void show_regs_common(void)
>  {
>  	const char *vendor, *product, *board;
> +	const char *machine_name = "x86";
> +	const char *kernel_type = "native";
> +
> +	if (x86_hyper) {
> +		machine_name = x86_hyper->name;
> +		kernel_type = "guest";
> +	}
>  
>  	vendor = dmi_get_system_info(DMI_SYS_VENDOR);
>  	if (!vendor)
> @@ -135,7 +143,9 @@ void show_regs_common(void)
>  	/* Board Name is optional */
>  	board = dmi_get_system_info(DMI_BOARD_NAME);
>  
> -	printk(KERN_DEFAULT "Pid: %d, comm: %.20s %s %s %.*s %s %s%s%s\n",
> +	printk(KERN_DEFAULT
> +	       "[%s %s kernel] Pid: %d, comm: %.20s %s %s %.*s %s %s%s%s\n",
> +	       machine_name, kernel_type,
>  	       current->pid, current->comm, print_tainted(),
>  	       init_utsname()->release,
>  	       (int)strcspn(init_utsname()->version, " "),

Ha, duplicate code doing almost the same thing!

I suspect you know what my next suggestion would be? :-)

Thanks,

	Ingo
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