[PATCH] drm/xen-front: fix pointer casts

[PATCH] drm/xen-front: fix pointer casts

[Oleksandr Andrushchenko]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

Building for a 32-bit target results in warnings from casting
between a 32-bit pointer and a 64-bit integer. Fix the warnings
by casting those pointers to uintptr_t first.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
---
 drivers/gpu/drm/xen/xen_drm_front.h       | 4 ++--
 drivers/gpu/drm/xen/xen_drm_front_shbuf.c | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/xen/xen_drm_front.h b/drivers/gpu/drm/xen/xen_drm_front.h
index 2c2479b571ae..8e15dbebc4ba 100644
--- a/drivers/gpu/drm/xen/xen_drm_front.h
+++ b/drivers/gpu/drm/xen/xen_drm_front.h
@@ -126,12 +126,12 @@ struct xen_drm_front_drm_info {
 
 static inline u64 xen_drm_front_fb_to_cookie(struct drm_framebuffer *fb)
 {
-	return (u64)fb;
+	return (u64)(uintptr_t)fb;
 }
 
 static inline u64 xen_drm_front_dbuf_to_cookie(struct drm_gem_object *gem_obj)
 {
-	return (u64)gem_obj;
+	return (u64)(uintptr_t)gem_obj;
 }
 
 int xen_drm_front_mode_set(struct xen_drm_front_drm_pipeline *pipeline,
diff --git a/drivers/gpu/drm/xen/xen_drm_front_shbuf.c b/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
index 8099cb343ae3..47fc93847765 100644
--- a/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
+++ b/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
@@ -122,7 +122,7 @@ static void guest_calc_num_grefs(struct xen_drm_front_shbuf *buf)
 }
 
 #define xen_page_to_vaddr(page) \
-		((phys_addr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
+		((phys_addr_t)(uintptr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
 
 static int backend_unmap(struct xen_drm_front_shbuf *buf)
 {
-- 
2.17.0

Re: [PATCH] drm/xen-front: fix pointer casts

[Juergen Gross]

On 21/05/18 09:39, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> 
> Building for a 32-bit target results in warnings from casting
> between a 32-bit pointer and a 64-bit integer. Fix the warnings
> by casting those pointers to uintptr_t first.
> 
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> ---
>  drivers/gpu/drm/xen/xen_drm_front.h       | 4 ++--
>  drivers/gpu/drm/xen/xen_drm_front_shbuf.c | 2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xen/xen_drm_front.h b/drivers/gpu/drm/xen/xen_drm_front.h
> index 2c2479b571ae..8e15dbebc4ba 100644
> --- a/drivers/gpu/drm/xen/xen_drm_front.h
> +++ b/drivers/gpu/drm/xen/xen_drm_front.h
> @@ -126,12 +126,12 @@ struct xen_drm_front_drm_info {
>  
>  static inline u64 xen_drm_front_fb_to_cookie(struct drm_framebuffer *fb)
>  {
> -	return (u64)fb;
> +	return (u64)(uintptr_t)fb;

Do you really still need the cast to u64?

>  }
>  
>  static inline u64 xen_drm_front_dbuf_to_cookie(struct drm_gem_object *gem_obj)
>  {
> -	return (u64)gem_obj;
> +	return (u64)(uintptr_t)gem_obj;
>  }
>  
>  int xen_drm_front_mode_set(struct xen_drm_front_drm_pipeline *pipeline,
> diff --git a/drivers/gpu/drm/xen/xen_drm_front_shbuf.c b/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
> index 8099cb343ae3..47fc93847765 100644
> --- a/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
> +++ b/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
> @@ -122,7 +122,7 @@ static void guest_calc_num_grefs(struct xen_drm_front_shbuf *buf)
>  }
>  
>  #define xen_page_to_vaddr(page) \
> -		((phys_addr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
> +		((phys_addr_t)(uintptr_t)pfn_to_kaddr(page_to_xen_pfn(page)))

phys_addr_t for a virtual address?


Juergen

Re: [PATCH] drm/xen-front: fix pointer casts

[Oleksandr Andrushchenko]

On 05/23/2018 12:19 PM, Juergen Gross wrote:
> On 21/05/18 09:39, Oleksandr Andrushchenko wrote:
>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>
>> Building for a 32-bit target results in warnings from casting
>> between a 32-bit pointer and a 64-bit integer. Fix the warnings
>> by casting those pointers to uintptr_t first.
>>
>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>> ---
>>   drivers/gpu/drm/xen/xen_drm_front.h       | 4 ++--
>>   drivers/gpu/drm/xen/xen_drm_front_shbuf.c | 2 +-
>>   2 files changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/xen/xen_drm_front.h b/drivers/gpu/drm/xen/xen_drm_front.h
>> index 2c2479b571ae..8e15dbebc4ba 100644
>> --- a/drivers/gpu/drm/xen/xen_drm_front.h
>> +++ b/drivers/gpu/drm/xen/xen_drm_front.h
>> @@ -126,12 +126,12 @@ struct xen_drm_front_drm_info {
>>   
>>   static inline u64 xen_drm_front_fb_to_cookie(struct drm_framebuffer *fb)
>>   {
>> -	return (u64)fb;
>> +	return (u64)(uintptr_t)fb;
> Do you really still need the cast to u64?
Indeed, I can remove (u64) now, thank you
>
>>   }
>>   
>>   static inline u64 xen_drm_front_dbuf_to_cookie(struct drm_gem_object *gem_obj)
>>   {
>> -	return (u64)gem_obj;
>> +	return (u64)(uintptr_t)gem_obj;
>>   }
>>   
>>   int xen_drm_front_mode_set(struct xen_drm_front_drm_pipeline *pipeline,
>> diff --git a/drivers/gpu/drm/xen/xen_drm_front_shbuf.c b/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
>> index 8099cb343ae3..47fc93847765 100644
>> --- a/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
>> +++ b/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
>> @@ -122,7 +122,7 @@ static void guest_calc_num_grefs(struct xen_drm_front_shbuf *buf)
>>   }
>>   
>>   #define xen_page_to_vaddr(page) \
>> -		((phys_addr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
>> +		((phys_addr_t)(uintptr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
> phys_addr_t for a virtual address?
This is because the resulting value is then passed to gnttab_set_map_op/
gnttab_set_unmap_op which expects host address to be passed as
phys_addr_t addr :(
Please see [1], [2]: regardless of the fact that xen_page_to_vaddr does
produce host address I have to convert it to phys_addr_t then to pass to 
[1] and [2].
Please also see [3], [4], [5] which either cast to phys_addr_t or
unsigned long or u64.
>
> Juergen

[1] 
https://elixir.bootlin.com/linux/v4.17-rc6/source/include/xen/grant_table.h#L147
[2] 
https://elixir.bootlin.com/linux/v4.17-rc6/source/include/xen/grant_table.h#L163
[3] 
https://elixir.bootlin.com/linux/v4.17-rc6/source/drivers/block/xen-blkback/blkback.c#L845
[4] 
https://elixir.bootlin.com/linux/v4.17-rc6/source/drivers/net/xen-netback/netback.c#L334
[5] 
https://elixir.bootlin.com/linux/v4.17-rc6/source/drivers/xen/xenbus/xenbus_client.c#L478

Re: [PATCH] drm/xen-front: fix pointer casts

[Juergen Gross]

On 23/05/18 12:00, Oleksandr Andrushchenko wrote:
> On 05/23/2018 12:19 PM, Juergen Gross wrote:
>> On 21/05/18 09:39, Oleksandr Andrushchenko wrote:
>>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>>
>>> Building for a 32-bit target results in warnings from casting
>>> between a 32-bit pointer and a 64-bit integer. Fix the warnings
>>> by casting those pointers to uintptr_t first.
>>>
>>> Signed-off-by: Oleksandr Andrushchenko
>>> <oleksandr_andrushchenko@epam.com>
>>> ---
>>>   drivers/gpu/drm/xen/xen_drm_front.h       | 4 ++--
>>>   drivers/gpu/drm/xen/xen_drm_front_shbuf.c | 2 +-
>>>   2 files changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/xen/xen_drm_front.h
>>> b/drivers/gpu/drm/xen/xen_drm_front.h
>>> index 2c2479b571ae..8e15dbebc4ba 100644
>>> --- a/drivers/gpu/drm/xen/xen_drm_front.h
>>> +++ b/drivers/gpu/drm/xen/xen_drm_front.h
>>> @@ -126,12 +126,12 @@ struct xen_drm_front_drm_info {
>>>     static inline u64 xen_drm_front_fb_to_cookie(struct
>>> drm_framebuffer *fb)
>>>   {
>>> -    return (u64)fb;
>>> +    return (u64)(uintptr_t)fb;
>> Do you really still need the cast to u64?
> Indeed, I can remove (u64) now, thank you
>>
>>>   }
>>>     static inline u64 xen_drm_front_dbuf_to_cookie(struct
>>> drm_gem_object *gem_obj)
>>>   {
>>> -    return (u64)gem_obj;
>>> +    return (u64)(uintptr_t)gem_obj;
>>>   }
>>>     int xen_drm_front_mode_set(struct xen_drm_front_drm_pipeline
>>> *pipeline,
>>> diff --git a/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
>>> b/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
>>> index 8099cb343ae3..47fc93847765 100644
>>> --- a/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
>>> +++ b/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
>>> @@ -122,7 +122,7 @@ static void guest_calc_num_grefs(struct
>>> xen_drm_front_shbuf *buf)
>>>   }
>>>     #define xen_page_to_vaddr(page) \
>>> -        ((phys_addr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
>>> +        ((phys_addr_t)(uintptr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
>> phys_addr_t for a virtual address?
> This is because the resulting value is then passed to gnttab_set_map_op/
> gnttab_set_unmap_op which expects host address to be passed as
> phys_addr_t addr :(

Okay, but this means the compiler should do the necessary cast when
you drop the cast to phys_addr_t in xen_page_to_vaddr(), as the cast
to uintptr_t is already producing an unsigned integer value which can
easily be promoted to more bits, right?


Juergen

Re: [PATCH] drm/xen-front: fix pointer casts

[Oleksandr Andrushchenko]

On 05/23/2018 02:06 PM, Juergen Gross wrote:
> On 23/05/18 12:00, Oleksandr Andrushchenko wrote:
>> On 05/23/2018 12:19 PM, Juergen Gross wrote:
>>> On 21/05/18 09:39, Oleksandr Andrushchenko wrote:
>>>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>>>
>>>> Building for a 32-bit target results in warnings from casting
>>>> between a 32-bit pointer and a 64-bit integer. Fix the warnings
>>>> by casting those pointers to uintptr_t first.
>>>>
>>>> Signed-off-by: Oleksandr Andrushchenko
>>>> <oleksandr_andrushchenko@epam.com>
>>>> ---
>>>>    drivers/gpu/drm/xen/xen_drm_front.h       | 4 ++--
>>>>    drivers/gpu/drm/xen/xen_drm_front_shbuf.c | 2 +-
>>>>    2 files changed, 3 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/xen/xen_drm_front.h
>>>> b/drivers/gpu/drm/xen/xen_drm_front.h
>>>> index 2c2479b571ae..8e15dbebc4ba 100644
>>>> --- a/drivers/gpu/drm/xen/xen_drm_front.h
>>>> +++ b/drivers/gpu/drm/xen/xen_drm_front.h
>>>> @@ -126,12 +126,12 @@ struct xen_drm_front_drm_info {
>>>>      static inline u64 xen_drm_front_fb_to_cookie(struct
>>>> drm_framebuffer *fb)
>>>>    {
>>>> -    return (u64)fb;
>>>> +    return (u64)(uintptr_t)fb;
>>> Do you really still need the cast to u64?
>> Indeed, I can remove (u64) now, thank you
>>>>    }
>>>>      static inline u64 xen_drm_front_dbuf_to_cookie(struct
>>>> drm_gem_object *gem_obj)
>>>>    {
>>>> -    return (u64)gem_obj;
>>>> +    return (u64)(uintptr_t)gem_obj;
>>>>    }
>>>>      int xen_drm_front_mode_set(struct xen_drm_front_drm_pipeline
>>>> *pipeline,
>>>> diff --git a/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
>>>> b/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
>>>> index 8099cb343ae3..47fc93847765 100644
>>>> --- a/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
>>>> +++ b/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
>>>> @@ -122,7 +122,7 @@ static void guest_calc_num_grefs(struct
>>>> xen_drm_front_shbuf *buf)
>>>>    }
>>>>      #define xen_page_to_vaddr(page) \
>>>> -        ((phys_addr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
>>>> +        ((phys_addr_t)(uintptr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
>>> phys_addr_t for a virtual address?
>> This is because the resulting value is then passed to gnttab_set_map_op/
>> gnttab_set_unmap_op which expects host address to be passed as
>> phys_addr_t addr :(
> Okay, but this means the compiler should do the necessary cast when
> you drop the cast to phys_addr_t in xen_page_to_vaddr(), as the cast
> to uintptr_t is already producing an unsigned integer value which can
> easily be promoted to more bits, right?
Right, so I can safely use:
  #define xen_page_to_vaddr(page) \
- ((phys_addr_t)(uintptr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
+               ((uintptr_t)pfn_to_kaddr(page_to_xen_pfn(page)))

>
> Juergen
Thank you for your time and comments,
Oleksandr