Re: [PATCH] jailhouse: Hold reference returned from of_find_xxx API

Re: [PATCH] jailhouse: Hold reference returned from of_find_xxx API

[Juergen Gross via Virtualization]

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On 15.09.22 04:23, Liang He wrote:
> In jailhouse_paravirt(), we should hold the reference returned from
> of_find_compatible_node() which has increased the refcount and then
> call of_node_put() with it when done.
> 
> Fixes: 63338a38db95 ("jailhouse: Provide detection for non-x86 systems")
> Signed-off-by: Liang He <windhl@126.com>
> Signed-off-by: Kelin Wang <wangkelin2023@163.com>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen

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Re: [PATCH] jailhouse: Hold reference returned from of_find_xxx API

[Srivatsa S. Bhat]

[ Adding author and reviewers of commit 63338a38db95 ]

On 9/14/22 7:23 PM, Liang He wrote:
> In jailhouse_paravirt(), we should hold the reference returned from
> of_find_compatible_node() which has increased the refcount and then
> call of_node_put() with it when done.
> 
> Fixes: 63338a38db95 ("jailhouse: Provide detection for non-x86 systems")
> Signed-off-by: Liang He <windhl@126.com>
> Signed-off-by: Kelin Wang <wangkelin2023@163.com>
> ---
>  include/linux/hypervisor.h | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/hypervisor.h b/include/linux/hypervisor.h
> index 9efbc54e35e5..7fe1e8c6211c 100644
> --- a/include/linux/hypervisor.h
> +++ b/include/linux/hypervisor.h
> @@ -27,7 +27,11 @@ static inline void hypervisor_pin_vcpu(int cpu)
>  
>  static inline bool jailhouse_paravirt(void)
>  {
> -	return of_find_compatible_node(NULL, NULL, "jailhouse,cell");
> +	struct device_node *np = of_find_compatible_node(NULL, NULL, "jailhouse,cell");
> +
> +	of_node_put(np);
> +
> +	return np;
>  }
>  

Thank you for the fix, but returning a pointer from a function with a
bool return type looks odd. Can we also fix that up please?


Regards,
Srivatsa
VMware Photon OS
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Re: Re: [PATCH] jailhouse: Hold reference returned from of_find_xxx API

[Andy Shevchenko]

On Fri, Sep 16, 2022 at 5:02 AM Liang He <windhl@126.com> wrote:
> At 2022-09-16 07:29:06, "Srivatsa S. Bhat" <srivatsa@csail.mit.edu> wrote:
> >On 9/14/22 7:23 PM, Liang He wrote:

..

> >>  static inline bool jailhouse_paravirt(void)
> >>  {
> >> -    return of_find_compatible_node(NULL, NULL, "jailhouse,cell");
> >> +    struct device_node *np = of_find_compatible_node(NULL, NULL, "jailhouse,cell");
> >> +
> >> +    of_node_put(np);
> >> +
> >> +    return np;
> >>  }
> >
> >Thank you for the fix, but returning a pointer from a function with a
> >bool return type looks odd. Can we also fix that up please?
> >
>
> Thanks for your review, how about following patch:
>
> -       return of_find_compatible_node(NULL, NULL, "jailhouse,cell");
> +       struct device_node *np = of_find_compatible_node(NULL, NULL, "jailhouse,cell");
> +
> +       of_node_put(np);
> +
> +       return (np==NULL);

This will be opposite to the above. Perhaps you wanted

  return  !!np;

Also possible (but why?)

  return np ? true : false;

-- 
With Best Regards,
Andy Shevchenko
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Re: Re: Re: [PATCH] jailhouse: Hold reference returned from of_find_xxx API

[Andy Shevchenko]

On Fri, Sep 16, 2022 at 10:09 AM Liang He <windhl@126.com> wrote:
> At 2022-09-16 13:38:39, "Andy Shevchenko" <andy.shevchenko@gmail.com> wrote:
> >On Fri, Sep 16, 2022 at 5:02 AM Liang He <windhl@126.com> wrote:
> >> At 2022-09-16 07:29:06, "Srivatsa S. Bhat" <srivatsa@csail.mit.edu> wrote:
> >> >On 9/14/22 7:23 PM, Liang He wrote:

...

> >> >>  static inline bool jailhouse_paravirt(void)
> >> >>  {
> >> >> -    return of_find_compatible_node(NULL, NULL, "jailhouse,cell");
> >> >> +    struct device_node *np = of_find_compatible_node(NULL, NULL, "jailhouse,cell");
> >> >> +
> >> >> +    of_node_put(np);
> >> >> +
> >> >> +    return np;
> >> >>  }
> >> >
> >> >Thank you for the fix, but returning a pointer from a function with a
> >> >bool return type looks odd. Can we also fix that up please?
> >>
> >> Thanks for your review, how about following patch:
> >>
> >> -       return of_find_compatible_node(NULL, NULL, "jailhouse,cell");
> >> +       struct device_node *np = of_find_compatible_node(NULL, NULL, "jailhouse,cell");
> >> +
> >> +       of_node_put(np);
> >> +
> >> +       return (np==NULL);
>
> >This will be opposite to the above. Perhaps you wanted
>
> Sorry, I wanted to use 'np!=NULL'
>
> >  return  !!np;
> >
> >Also possible (but why?)
> >
> >  return np ? true : false;
>
> So, can I chose 'return np?true: false;' as the final patch?

Of course you can, it's up to the maintainer(s) what to accept.

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With Best Regards,
Andy Shevchenko
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