[PATCH v2] misc: pvpanic: introduce device capability

[PATCH v2] misc: pvpanic: introduce device capability

[zhenwei pi]

According to pvpanic spec:
https://git.qemu.org/?p=qemu.git;a=blob_plain;f=docs/specs/pvpanic.txt

The guest should determine pvpanic capability by RDPT, so initialize
capability during device probing. There is no need to register panic
notifier callback function if no events supported.

Before sending event to host side, check capability firstly.
Suggested by Paolo, export capability of pvpanic device by read-only
module parameter.

Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
---
 drivers/misc/pvpanic.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/misc/pvpanic.c b/drivers/misc/pvpanic.c
index 951b37da5e3c..c55a9d2fd001 100644
--- a/drivers/misc/pvpanic.c
+++ b/drivers/misc/pvpanic.c
@@ -19,6 +19,9 @@
 #include <uapi/misc/pvpanic.h>
 
 static void __iomem *base;
+static unsigned int capability = PVPANIC_PANICKED | PVPANIC_CRASH_LOADED;
+module_param(capability, uint, 0444);
+MODULE_PARM_DESC(capability, "capability of pvpanic device");
 
 MODULE_AUTHOR("Hu Tao <hutao@cn.fujitsu.com>");
 MODULE_DESCRIPTION("pvpanic device driver");
@@ -27,7 +30,8 @@ MODULE_LICENSE("GPL");
 static void
 pvpanic_send_event(unsigned int event)
 {
-	iowrite8(event, base);
+	if (event & capability)
+		iowrite8(event, base);
 }
 
 static int
@@ -62,8 +66,12 @@ static int pvpanic_mmio_probe(struct platform_device *pdev)
 	if (IS_ERR(base))
 		return PTR_ERR(base);
 
-	atomic_notifier_chain_register(&panic_notifier_list,
-				       &pvpanic_panic_nb);
+	/* initlize capability by RDPT */
+	capability &= ioread8(base);
+
+	if (capability)
+		atomic_notifier_chain_register(&panic_notifier_list,
+					       &pvpanic_panic_nb);
 
 	return 0;
 }
@@ -71,8 +79,9 @@ static int pvpanic_mmio_probe(struct platform_device *pdev)
 static int pvpanic_mmio_remove(struct platform_device *pdev)
 {
 
-	atomic_notifier_chain_unregister(&panic_notifier_list,
-					 &pvpanic_panic_nb);
+	if (capability)
+		atomic_notifier_chain_unregister(&panic_notifier_list,
+						 &pvpanic_panic_nb);
 
 	return 0;
 }
-- 
2.25.1

Re: [PATCH v2] misc: pvpanic: introduce device capability

[Greg KH]

On Fri, Jan 08, 2021 at 07:17:10PM +0800, zhenwei pi wrote:
> According to pvpanic spec:
> https://git.qemu.org/?p=qemu.git;a=blob_plain;f=docs/specs/pvpanic.txt
> 
> The guest should determine pvpanic capability by RDPT, so initialize
> capability during device probing. There is no need to register panic
> notifier callback function if no events supported.
> 
> Before sending event to host side, check capability firstly.
> Suggested by Paolo, export capability of pvpanic device by read-only
> module parameter.
> 
> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
> ---
>  drivers/misc/pvpanic.c | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/misc/pvpanic.c b/drivers/misc/pvpanic.c
> index 951b37da5e3c..c55a9d2fd001 100644
> --- a/drivers/misc/pvpanic.c
> +++ b/drivers/misc/pvpanic.c
> @@ -19,6 +19,9 @@
>  #include <uapi/misc/pvpanic.h>
>  
>  static void __iomem *base;
> +static unsigned int capability = PVPANIC_PANICKED | PVPANIC_CRASH_LOADED;
> +module_param(capability, uint, 0444);
> +MODULE_PARM_DESC(capability, "capability of pvpanic device");
>  
>  MODULE_AUTHOR("Hu Tao <hutao@cn.fujitsu.com>");
>  MODULE_DESCRIPTION("pvpanic device driver");
> @@ -27,7 +30,8 @@ MODULE_LICENSE("GPL");
>  static void
>  pvpanic_send_event(unsigned int event)
>  {
> -	iowrite8(event, base);
> +	if (event & capability)
> +		iowrite8(event, base);
>  }
>  
>  static int
> @@ -62,8 +66,12 @@ static int pvpanic_mmio_probe(struct platform_device *pdev)
>  	if (IS_ERR(base))
>  		return PTR_ERR(base);
>  
> -	atomic_notifier_chain_register(&panic_notifier_list,
> -				       &pvpanic_panic_nb);
> +	/* initlize capability by RDPT */
> +	capability &= ioread8(base);
> +
> +	if (capability)
> +		atomic_notifier_chain_register(&panic_notifier_list,
> +					       &pvpanic_panic_nb);
>  
>  	return 0;
>  }
> @@ -71,8 +79,9 @@ static int pvpanic_mmio_probe(struct platform_device *pdev)
>  static int pvpanic_mmio_remove(struct platform_device *pdev)
>  {
>  
> -	atomic_notifier_chain_unregister(&panic_notifier_list,
> -					 &pvpanic_panic_nb);
> +	if (capability)
> +		atomic_notifier_chain_unregister(&panic_notifier_list,
> +						 &pvpanic_panic_nb);
>  
>  	return 0;
>  }
> -- 
> 2.25.1
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:

- This looks like a new version of a previously submitted patch, but you
  did not list below the --- line any changes from the previous version.
  Please read the section entitled "The canonical patch format" in the
  kernel file, Documentation/SubmittingPatches for what needs to be done
  here to properly describe this.

If you wish to discuss this problem further, or you have questions about
how to resolve this issue, please feel free to respond to this email and
Greg will reply once he has dug out from the pending patches received
from other developers.

thanks,

greg k-h's patch email bot

Re: [PATCH v2] misc: pvpanic: introduce device capability

[Greg KH]

On Fri, Jan 08, 2021 at 07:17:10PM +0800, zhenwei pi wrote:
> According to pvpanic spec:
> https://git.qemu.org/?p=qemu.git;a=blob_plain;f=docs/specs/pvpanic.txt
> 
> The guest should determine pvpanic capability by RDPT, so initialize
> capability during device probing. There is no need to register panic
> notifier callback function if no events supported.
> 
> Before sending event to host side, check capability firstly.
> Suggested by Paolo, export capability of pvpanic device by read-only
> module parameter.
> 
> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
> ---
>  drivers/misc/pvpanic.c | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/misc/pvpanic.c b/drivers/misc/pvpanic.c
> index 951b37da5e3c..c55a9d2fd001 100644
> --- a/drivers/misc/pvpanic.c
> +++ b/drivers/misc/pvpanic.c
> @@ -19,6 +19,9 @@
>  #include <uapi/misc/pvpanic.h>
>  
>  static void __iomem *base;
> +static unsigned int capability = PVPANIC_PANICKED | PVPANIC_CRASH_LOADED;
> +module_param(capability, uint, 0444);
> +MODULE_PARM_DESC(capability, "capability of pvpanic device");

This is not the 1990's, please do not add new module parameters :(

Use sysfs, and properly document the file in Documentation/ABI/

thanks,

greg k-h

Re: [PATCH v2] misc: pvpanic: introduce device capability

[Paolo Bonzini]

On 08/01/21 12:28, Greg KH wrote:
>>   static void __iomem *base;
>> +static unsigned int capability = PVPANIC_PANICKED | PVPANIC_CRASH_LOADED;
>> +module_param(capability, uint, 0444);
>> +MODULE_PARM_DESC(capability, "capability of pvpanic device");
> This is not the 1990's, please do not add new module parameters:(

Note that the parameter can also be used to _limit_ which capabilities 
the driver uses:

v1:

> +	/* initlize capability by RDPT */
> +	capability = ioread8(base);

v2:

> +	/* initlize capability by RDPT */
> +	capability &= ioread8(base);

Of course it would have helped if there was a summary of v1->v2 changes 
in the message. :)

Paolo

> Use sysfs, and properly document the file in Documentation/ABI/