[PATCH 1/2] wordpart.h: Helpers for making u16/u32/u64 values

[PATCH 1/2] wordpart.h: Helpers for making u16/u32/u64 values

[Michal Wajdeczko]

It is quite common practice to make u16, u32 or u64 values from
smaller words.  Add simple helpers for that.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
---
v2: new macro names due to conflict with crypto/aria.h
    explicit cast and truncation everywhere (Alexey)
    moved to wordpart.h (Andy)
---
Cc: Kees Cook <keescook@chromium.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Jani Nikula <jani.nikula@intel.com>
---
 include/linux/wordpart.h | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/include/linux/wordpart.h b/include/linux/wordpart.h
index f6f8f83b15b0..8c75a5355112 100644
--- a/include/linux/wordpart.h
+++ b/include/linux/wordpart.h
@@ -31,6 +31,38 @@
  */
 #define lower_16_bits(n) ((u16)((n) & 0xffff))
 
+/**
+ * make_u16_from_u8 - make u16 value from two u8 values
+ * @hi: value representing upper 8 bits
+ * @lo: value representing lower 8 bits
+ */
+#define make_u16_from_u8(hi, lo) ((u16)((u16)(u8)(hi) << 8 | (u8)(lo)))
+
+/**
+ * make_u32_from_u16 - make u32 value from two u16 values
+ * @hi: value representing upper 16 bits
+ * @lo: value representing lower 16 bits
+ */
+#define make_u32_from_u16(hi, lo) ((u32)((u32)(u16)(hi) << 16 | (u16)(lo)))
+
+/**
+ * make_u32_from_u8 - make u32 value from u8 values
+ * @a: value representing bits 31-24
+ * @b: value representing bits 23-16
+ * @c: value representing bits 15-8
+ * @d: value representing bits 7-0
+ */
+#define make_u32_from_u8(a, b, c, d) \
+	make_u32_from_u16(make_u16_from_u8((a), (b)), \
+			  make_u16_from_u8((c), (d)))
+
+/**
+ * make_u64_from_u32 - make u64 value from two u32 values
+ * @hi: value representing upper 32 bits
+ * @lo: value representing lower 32 bits
+ */
+#define make_u64_from_u32(hi, lo) ((u64)((u64)(u32)(hi) << 32 | (u32)(lo)))
+
 /**
  * REPEAT_BYTE - repeat the value @x multiple times as an unsigned long value
  * @x: value to repeat
-- 
2.43.0

[PATCH 2/2] drm/xe: Prefer make_u64_from_u32() over local macro

[Michal Wajdeczko]

Stop using private make_u64() macro if there is a generic one.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
---
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/xe/xe_gt_pagefault.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_gt_pagefault.c b/drivers/gpu/drm/xe/xe_gt_pagefault.c
index 59a70d2e0a7a..ac90eda39ceb 100644
--- a/drivers/gpu/drm/xe/xe_gt_pagefault.c
+++ b/drivers/gpu/drm/xe/xe_gt_pagefault.c
@@ -7,6 +7,7 @@
 
 #include <linux/bitfield.h>
 #include <linux/circ_buf.h>
+#include <linux/wordpart.h>
 
 #include <drm/drm_exec.h>
 #include <drm/drm_managed.h>
@@ -549,8 +550,6 @@ static int handle_acc(struct xe_gt *gt, struct acc *acc)
 	return ret;
 }
 
-#define make_u64(hi__, low__)  ((u64)(hi__) << 32 | (u64)(low__))
-
 #define ACC_MSG_LEN_DW        4
 
 static bool get_acc(struct acc_queue *acc_queue, struct acc *acc)
@@ -571,8 +570,8 @@ static bool get_acc(struct acc_queue *acc_queue, struct acc *acc)
 		acc->asid =  FIELD_GET(ACC_ASID, desc->dw1);
 		acc->vfid =  FIELD_GET(ACC_VFID, desc->dw2);
 		acc->access_type = FIELD_GET(ACC_TYPE, desc->dw0);
-		acc->va_range_base = make_u64(desc->dw3 & ACC_VIRTUAL_ADDR_RANGE_HI,
-					      desc->dw2 & ACC_VIRTUAL_ADDR_RANGE_LO);
+		acc->va_range_base = make_u64_from_u32(desc->dw3 & ACC_VIRTUAL_ADDR_RANGE_HI,
+						       desc->dw2 & ACC_VIRTUAL_ADDR_RANGE_LO);
 
 		acc_queue->head = (acc_queue->head + ACC_MSG_LEN_DW) %
 				  ACC_QUEUE_NUM_DW;
-- 
2.43.0

Re: [PATCH 1/2] wordpart.h: Helpers for making u16/u32/u64 values

[Kees Cook]

On Wed, Feb 14, 2024 at 10:46:53PM +0100, Michal Wajdeczko wrote:
> It is quite common practice to make u16, u32 or u64 values from
> smaller words.  Add simple helpers for that.
> 
> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
> ---
> v2: new macro names due to conflict with crypto/aria.h
>     explicit cast and truncation everywhere (Alexey)
>     moved to wordpart.h (Andy)
> ---
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Cc: Alexey Dobriyan <adobriyan@gmail.com>
> Cc: Jani Nikula <jani.nikula@intel.com>
> ---
>  include/linux/wordpart.h | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/include/linux/wordpart.h b/include/linux/wordpart.h
> index f6f8f83b15b0..8c75a5355112 100644
> --- a/include/linux/wordpart.h
> +++ b/include/linux/wordpart.h
> @@ -31,6 +31,38 @@
>   */
>  #define lower_16_bits(n) ((u16)((n) & 0xffff))
>  
> +/**
> + * make_u16_from_u8 - make u16 value from two u8 values
> + * @hi: value representing upper 8 bits
> + * @lo: value representing lower 8 bits
> + */
> +#define make_u16_from_u8(hi, lo) ((u16)((u16)(u8)(hi) << 8 | (u8)(lo)))

Do we want to actually do type validation here? Right now it's just
cast/truncating, which based on the version log is by design. Is silent
truncation the right thing to do?

-- 
Kees Cook

Re: [PATCH 1/2] wordpart.h: Helpers for making u16/u32/u64 values

[Michal Wajdeczko]

On 14.02.2024 23:09, Kees Cook wrote:
> On Wed, Feb 14, 2024 at 10:46:53PM +0100, Michal Wajdeczko wrote:
>> It is quite common practice to make u16, u32 or u64 values from
>> smaller words.  Add simple helpers for that.
>>
>> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
>> ---
>> v2: new macro names due to conflict with crypto/aria.h
>>     explicit cast and truncation everywhere (Alexey)
>>     moved to wordpart.h (Andy)
>> ---
>> Cc: Kees Cook <keescook@chromium.org>
>> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>> Cc: Alexey Dobriyan <adobriyan@gmail.com>
>> Cc: Jani Nikula <jani.nikula@intel.com>
>> ---
>>  include/linux/wordpart.h | 32 ++++++++++++++++++++++++++++++++
>>  1 file changed, 32 insertions(+)
>>
>> diff --git a/include/linux/wordpart.h b/include/linux/wordpart.h
>> index f6f8f83b15b0..8c75a5355112 100644
>> --- a/include/linux/wordpart.h
>> +++ b/include/linux/wordpart.h
>> @@ -31,6 +31,38 @@
>>   */
>>  #define lower_16_bits(n) ((u16)((n) & 0xffff))
>>  
>> +/**
>> + * make_u16_from_u8 - make u16 value from two u8 values
>> + * @hi: value representing upper 8 bits
>> + * @lo: value representing lower 8 bits
>> + */
>> +#define make_u16_from_u8(hi, lo) ((u16)((u16)(u8)(hi) << 8 | (u8)(lo)))
> 
> Do we want to actually do type validation here? Right now it's just
> cast/truncating, which based on the version log is by design. Is silent
> truncation the right thing to do?

note that even FIELD_PREP() is doing silent truncation and these macros
here could be treated as specialized/simplified variants of FIELD_PREP()
as alternate implementation can look like:

#define make_u16_from_u8(hi, lo) \
	((u16)(FIELD_PREP_CONST(GENMASK(15, 8), (hi)) | \
	       FIELD_PREP_CONST(GENMASK(7, 0), (lo))))

#define make_u32_from_u16(hi, lo) \
	((u32)(FIELD_PREP_CONST(GENMASK(31, 16), (hi)) | \
	       FIELD_PREP_CONST(GENMASK(15, 0), (lo))))

#define make_u64_from_u32(hi, lo) \
	((u64)(FIELD_PREP_CONST(GENMASK_ULL(63, 32), (hi)) | \
	       FIELD_PREP_CONST(GENMASK_ULL(31, 0), (lo))))

but then it will not match simplicity of the lower|upper_XX_bits macros

Re: [PATCH 1/2] wordpart.h: Helpers for making u16/u32/u64 values

[Kees Cook]

On Thu, Feb 15, 2024 at 09:40:40PM +0100, Michal Wajdeczko wrote:
> On 14.02.2024 23:09, Kees Cook wrote:
> > On Wed, Feb 14, 2024 at 10:46:53PM +0100, Michal Wajdeczko wrote:
> >> It is quite common practice to make u16, u32 or u64 values from
> >> smaller words.  Add simple helpers for that.
> >>
> >> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
> >> ---
> >> v2: new macro names due to conflict with crypto/aria.h
> >>     explicit cast and truncation everywhere (Alexey)
> >>     moved to wordpart.h (Andy)
> >> ---
> >> Cc: Kees Cook <keescook@chromium.org>
> >> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> >> Cc: Alexey Dobriyan <adobriyan@gmail.com>
> >> Cc: Jani Nikula <jani.nikula@intel.com>
> >> ---
> >>  include/linux/wordpart.h | 32 ++++++++++++++++++++++++++++++++
> >>  1 file changed, 32 insertions(+)
> >>
> >> diff --git a/include/linux/wordpart.h b/include/linux/wordpart.h
> >> index f6f8f83b15b0..8c75a5355112 100644
> >> --- a/include/linux/wordpart.h
> >> +++ b/include/linux/wordpart.h
> >> @@ -31,6 +31,38 @@
> >>   */
> >>  #define lower_16_bits(n) ((u16)((n) & 0xffff))
> >>  
> >> +/**
> >> + * make_u16_from_u8 - make u16 value from two u8 values
> >> + * @hi: value representing upper 8 bits
> >> + * @lo: value representing lower 8 bits
> >> + */
> >> +#define make_u16_from_u8(hi, lo) ((u16)((u16)(u8)(hi) << 8 | (u8)(lo)))
> > 
> > Do we want to actually do type validation here? Right now it's just
> > cast/truncating, which based on the version log is by design. Is silent
> > truncation the right thing to do?
> 
> note that even FIELD_PREP() is doing silent truncation and these macros
> here could be treated as specialized/simplified variants of FIELD_PREP()
> as alternate implementation can look like:

Also, isn't all of this endian-specific?

-- 
Kees Cook

Re: [PATCH 1/2] wordpart.h: Helpers for making u16/u32/u64 values

[Michal Wajdeczko]

On 15.02.2024 23:47, Kees Cook wrote:
> On Thu, Feb 15, 2024 at 09:40:40PM +0100, Michal Wajdeczko wrote:
>> On 14.02.2024 23:09, Kees Cook wrote:
>>> On Wed, Feb 14, 2024 at 10:46:53PM +0100, Michal Wajdeczko wrote:
>>>> It is quite common practice to make u16, u32 or u64 values from
>>>> smaller words.  Add simple helpers for that.
>>>>
>>>> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
>>>> ---
>>>> v2: new macro names due to conflict with crypto/aria.h
>>>>     explicit cast and truncation everywhere (Alexey)
>>>>     moved to wordpart.h (Andy)
>>>> ---
>>>> Cc: Kees Cook <keescook@chromium.org>
>>>> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>>>> Cc: Alexey Dobriyan <adobriyan@gmail.com>
>>>> Cc: Jani Nikula <jani.nikula@intel.com>
>>>> ---
>>>>  include/linux/wordpart.h | 32 ++++++++++++++++++++++++++++++++
>>>>  1 file changed, 32 insertions(+)
>>>>
>>>> diff --git a/include/linux/wordpart.h b/include/linux/wordpart.h
>>>> index f6f8f83b15b0..8c75a5355112 100644
>>>> --- a/include/linux/wordpart.h
>>>> +++ b/include/linux/wordpart.h
>>>> @@ -31,6 +31,38 @@
>>>>   */
>>>>  #define lower_16_bits(n) ((u16)((n) & 0xffff))
>>>>  
>>>> +/**
>>>> + * make_u16_from_u8 - make u16 value from two u8 values
>>>> + * @hi: value representing upper 8 bits
>>>> + * @lo: value representing lower 8 bits
>>>> + */
>>>> +#define make_u16_from_u8(hi, lo) ((u16)((u16)(u8)(hi) << 8 | (u8)(lo)))
>>>
>>> Do we want to actually do type validation here? Right now it's just
>>> cast/truncating, which based on the version log is by design. Is silent
>>> truncation the right thing to do?
>>
>> note that even FIELD_PREP() is doing silent truncation and these macros
>> here could be treated as specialized/simplified variants of FIELD_PREP()
>> as alternate implementation can look like:
> 
> Also, isn't all of this endian-specific?

endianness shouldn't matter here

so I guess the only question now is whether we want to have simple
direct macros like lower|upper_bits() or go with macros build on top of
the FIELD_PREP_CONST() or drop the idea completely and force the drivers
to invent the wheel on its own

Re: [PATCH 1/2] wordpart.h: Helpers for making u16/u32/u64 values

[Jani Nikula]

On Tue, 26 Mar 2024, Michal Wajdeczko <michal.wajdeczko@intel.com> wrote:
> On 15.02.2024 23:47, Kees Cook wrote:
>> On Thu, Feb 15, 2024 at 09:40:40PM +0100, Michal Wajdeczko wrote:
>>> On 14.02.2024 23:09, Kees Cook wrote:
>>>> On Wed, Feb 14, 2024 at 10:46:53PM +0100, Michal Wajdeczko wrote:
>>>>> It is quite common practice to make u16, u32 or u64 values from
>>>>> smaller words.  Add simple helpers for that.
>>>>>
>>>>> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
>>>>> ---
>>>>> v2: new macro names due to conflict with crypto/aria.h
>>>>>     explicit cast and truncation everywhere (Alexey)
>>>>>     moved to wordpart.h (Andy)
>>>>> ---
>>>>> Cc: Kees Cook <keescook@chromium.org>
>>>>> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>>>>> Cc: Alexey Dobriyan <adobriyan@gmail.com>
>>>>> Cc: Jani Nikula <jani.nikula@intel.com>
>>>>> ---
>>>>>  include/linux/wordpart.h | 32 ++++++++++++++++++++++++++++++++
>>>>>  1 file changed, 32 insertions(+)
>>>>>
>>>>> diff --git a/include/linux/wordpart.h b/include/linux/wordpart.h
>>>>> index f6f8f83b15b0..8c75a5355112 100644
>>>>> --- a/include/linux/wordpart.h
>>>>> +++ b/include/linux/wordpart.h
>>>>> @@ -31,6 +31,38 @@
>>>>>   */
>>>>>  #define lower_16_bits(n) ((u16)((n) & 0xffff))
>>>>>  
>>>>> +/**
>>>>> + * make_u16_from_u8 - make u16 value from two u8 values
>>>>> + * @hi: value representing upper 8 bits
>>>>> + * @lo: value representing lower 8 bits
>>>>> + */
>>>>> +#define make_u16_from_u8(hi, lo) ((u16)((u16)(u8)(hi) << 8 | (u8)(lo)))
>>>>
>>>> Do we want to actually do type validation here? Right now it's just
>>>> cast/truncating, which based on the version log is by design. Is silent
>>>> truncation the right thing to do?

Doesn't the name imply strongly enough that we're only interested in the
N bits from each parameter? I think not truncating makes these harder to
use (if it means e.g. casting on the caller side).

>>>
>>> note that even FIELD_PREP() is doing silent truncation and these macros
>>> here could be treated as specialized/simplified variants of FIELD_PREP()
>>> as alternate implementation can look like:
>> 
>> Also, isn't all of this endian-specific?

None of this assumes endianness.

> endianness shouldn't matter here
>
> so I guess the only question now is whether we want to have simple
> direct macros like lower|upper_bits() or go with macros build on top of
> the FIELD_PREP_CONST() or drop the idea completely and force the drivers
> to invent the wheel on its own

Yeah, please let's do this so we don't have to keep adding them to
drivers.

BR,
Jani.


-- 
Jani Nikula, Intel