Re: [PATCH v9 03/15] xen/bitops: implement fls{l}() in common logic
On 17.05.2024 11:06, Oleksii K. wrote:
> On Wed, 2024-05-15 at 11:09 +0200, Jan Beulich wrote:
>> But this then needs carrying through to ...
>>
>>> --- a/xen/arch/arm/include/asm/arm64/bitops.h
>>> +++ b/xen/arch/arm/include/asm/arm64/bitops.h
>>> @@ -22,17 +22,15 @@ static /*__*/always_inline unsigned long
>>> __ffs(unsigned long word)
>>> */
>>> #define ffz(x) __ffs(~(x))
>>>
>>> -static inline int flsl(unsigned long x)
>>> +static inline int arch_flsl(unsigned long x)
>>
>> ... e.g. here. You don't want to introduce signed/unsigned
>> mismatches.
> Is it critical for x86 to return int for flsl() and fls() or I can
> update the return type for x86 too?
The return types ought to be changed imo, for everything to end up
consistent.
>static always_inline int arch_flsl(unsigned long x)
>{
>long r;
>
>asm ( "bsr %1,%0\n\t"
> "jnz 1f\n\t"
> "mov $-1,%0\n"
> "1:" : "=r" (r) : "rm" (x));
>return (int)r+1;
>}
>#define arch_flsl arch_flsl
>
>static always_inline int arch_fls(unsigned int x)
>{
>int r;
>
>asm ( "bsr %1,%0\n\t"
> "jnz 1f\n\t"
> "mov $-1,%0\n"
> "1:" : "=r" (r) : "rm" (x));
>return r + 1;
>}
>#define arch_fls arch_fls
>
> Any specific reason why 'long' and 'int' types for r are used?
I don't think so. I expect it merely fits with no-one having cared about
signedness back at the time.
Jan
Re: [PATCH v9 03/15] xen/bitops: implement fls{l}() in common logic
On Wed, 2024-05-15 at 11:09 +0200, Jan Beulich wrote:
> But this then needs carrying through to ...
>
> > --- a/xen/arch/arm/include/asm/arm64/bitops.h
> > +++ b/xen/arch/arm/include/asm/arm64/bitops.h
> > @@ -22,17 +22,15 @@ static /*__*/always_inline unsigned long
> > __ffs(unsigned long word)
> > */
> > #define ffz(x) __ffs(~(x))
> >
> > -static inline int flsl(unsigned long x)
> > +static inline int arch_flsl(unsigned long x)
>
> ... e.g. here. You don't want to introduce signed/unsigned
> mismatches.
Is it critical for x86 to return int for flsl() and fls() or I can
update the return type for x86 too?
static always_inline int arch_flsl(unsigned long x)
{
long r;
asm ( "bsr %1,%0\n\t"
"jnz 1f\n\t"
"mov $-1,%0\n"
"1:" : "=r" (r) : "rm" (x));
return (int)r+1;
}
#define arch_flsl arch_flsl
static always_inline int arch_fls(unsigned int x)
{
int r;
asm ( "bsr %1,%0\n\t"
"jnz 1f\n\t"
"mov $-1,%0\n"
"1:" : "=r" (r) : "rm" (x));
return r + 1;
}
#define arch_fls arch_fls
Any specific reason why 'long' and 'int' types for r are used?
~ Oleksii
Re: [PATCH v9 03/15] xen/bitops: implement fls{l}() in common logic
On Wed, 2024-05-15 at 16:07 +0200, Jan Beulich wrote: > On 15.05.2024 15:55, Oleksii K. wrote: > > On Wed, 2024-05-15 at 11:09 +0200, Jan Beulich wrote: > > > On 06.05.2024 12:15, Oleksii Kurochko wrote: > > > > Changes in V9: > > > > - update return type of fls and flsl() to unsigned int to be > > > > aligned with other > > > > bit ops. > > > > > > But this then needs carrying through to ... > > > > > > > --- a/xen/arch/arm/include/asm/arm64/bitops.h > > > > +++ b/xen/arch/arm/include/asm/arm64/bitops.h > > > > @@ -22,17 +22,15 @@ static /*__*/always_inline unsigned long > > > > __ffs(unsigned long word) > > > > */ > > > > #define ffz(x) __ffs(~(x)) > > > > > > > > -static inline int flsl(unsigned long x) > > > > +static inline int arch_flsl(unsigned long x) > > > > > > ... e.g. here. You don't want to introduce signed/unsigned > > > mismatches. > > Do you mean that generic flsl() uses 'unsigned int' as a return > > type, > > but arch_flsl continue to use 'int'? > > Yes. > > > > Also why do you keep "inline" here, while ... > > > > > > > --- a/xen/arch/x86/include/asm/bitops.h > > > > +++ b/xen/arch/x86/include/asm/bitops.h > > > > @@ -425,7 +425,7 @@ static always_inline unsigned int > > > > arch_ffsl(unsigned long x) > > > > * > > > > * This is defined the same way as ffs. > > > > */ > > > > -static inline int flsl(unsigned long x) > > > > +static always_inline int arch_flsl(unsigned long x) > > > > > > ... you switch to always_inline here? > > Because Adnrew's patch with bitops.h for x86 changes to > > always_inline, > > so to be consistent, at least, for architecture. > > And why not extend this to Arm? No specific reason, just wanted to do minimal amount of necessary changes. I'll do that in the the next patch version. ~ Oleksii
Re: [PATCH v9 03/15] xen/bitops: implement fls{l}() in common logic
On 15.05.2024 15:55, Oleksii K. wrote: > On Wed, 2024-05-15 at 11:09 +0200, Jan Beulich wrote: >> On 06.05.2024 12:15, Oleksii Kurochko wrote: >>> Changes in V9: >>> - update return type of fls and flsl() to unsigned int to be >>> aligned with other >>> bit ops. >> >> But this then needs carrying through to ... >> >>> --- a/xen/arch/arm/include/asm/arm64/bitops.h >>> +++ b/xen/arch/arm/include/asm/arm64/bitops.h >>> @@ -22,17 +22,15 @@ static /*__*/always_inline unsigned long >>> __ffs(unsigned long word) >>> */ >>> #define ffz(x) __ffs(~(x)) >>> >>> -static inline int flsl(unsigned long x) >>> +static inline int arch_flsl(unsigned long x) >> >> ... e.g. here. You don't want to introduce signed/unsigned >> mismatches. > Do you mean that generic flsl() uses 'unsigned int' as a return type, > but arch_flsl continue to use 'int'? Yes. >> Also why do you keep "inline" here, while ... >> >>> --- a/xen/arch/x86/include/asm/bitops.h >>> +++ b/xen/arch/x86/include/asm/bitops.h >>> @@ -425,7 +425,7 @@ static always_inline unsigned int >>> arch_ffsl(unsigned long x) >>> * >>> * This is defined the same way as ffs. >>> */ >>> -static inline int flsl(unsigned long x) >>> +static always_inline int arch_flsl(unsigned long x) >> >> ... you switch to always_inline here? > Because Adnrew's patch with bitops.h for x86 changes to always_inline, > so to be consistent, at least, for architecture. And why not extend this to Arm? Jan
Re: [PATCH v9 03/15] xen/bitops: implement fls{l}() in common logic
On Wed, 2024-05-15 at 11:09 +0200, Jan Beulich wrote: > On 06.05.2024 12:15, Oleksii Kurochko wrote: > > Changes in V9: > > - update return type of fls and flsl() to unsigned int to be > > aligned with other > > bit ops. > > But this then needs carrying through to ... > > > --- a/xen/arch/arm/include/asm/arm64/bitops.h > > +++ b/xen/arch/arm/include/asm/arm64/bitops.h > > @@ -22,17 +22,15 @@ static /*__*/always_inline unsigned long > > __ffs(unsigned long word) > > */ > > #define ffz(x) __ffs(~(x)) > > > > -static inline int flsl(unsigned long x) > > +static inline int arch_flsl(unsigned long x) > > ... e.g. here. You don't want to introduce signed/unsigned > mismatches. Do you mean that generic flsl() uses 'unsigned int' as a return type, but arch_flsl continue to use 'int'? > > Also why do you keep "inline" here, while ... > > > --- a/xen/arch/x86/include/asm/bitops.h > > +++ b/xen/arch/x86/include/asm/bitops.h > > @@ -425,7 +425,7 @@ static always_inline unsigned int > > arch_ffsl(unsigned long x) > > * > > * This is defined the same way as ffs. > > */ > > -static inline int flsl(unsigned long x) > > +static always_inline int arch_flsl(unsigned long x) > > ... you switch to always_inline here? Because Adnrew's patch with bitops.h for x86 changes to always_inline, so to be consistent, at least, for architecture. ~ Oleksii > > (replying out of order) > > > --- a/xen/arch/arm/include/asm/arm32/bitops.h > > +++ b/xen/arch/arm/include/asm/arm32/bitops.h > > @@ -1,7 +1,7 @@ > > #ifndef _ARM_ARM32_BITOPS_H > > #define _ARM_ARM32_BITOPS_H > > > > -#define flsl fls > > +#define arch_flsl fls > > It's the Arm maintainers to ultimately judge, but I'd be inclined to > suggest > > #define arch_flsl arch_fls > > instead. That's not only behaviorally closer to what was there > before, but > also reduces (a tiny bit) the amount of work the compiler needs to > carry out. > > Jan
Re: [PATCH v9 03/15] xen/bitops: implement fls{l}() in common logic
On 06.05.2024 12:15, Oleksii Kurochko wrote: > Changes in V9: > - update return type of fls and flsl() to unsigned int to be aligned with > other >bit ops. But this then needs carrying through to ... > --- a/xen/arch/arm/include/asm/arm64/bitops.h > +++ b/xen/arch/arm/include/asm/arm64/bitops.h > @@ -22,17 +22,15 @@ static /*__*/always_inline unsigned long __ffs(unsigned > long word) > */ > #define ffz(x) __ffs(~(x)) > > -static inline int flsl(unsigned long x) > +static inline int arch_flsl(unsigned long x) ... e.g. here. You don't want to introduce signed/unsigned mismatches. Also why do you keep "inline" here, while ... > --- a/xen/arch/x86/include/asm/bitops.h > +++ b/xen/arch/x86/include/asm/bitops.h > @@ -425,7 +425,7 @@ static always_inline unsigned int arch_ffsl(unsigned long > x) > * > * This is defined the same way as ffs. > */ > -static inline int flsl(unsigned long x) > +static always_inline int arch_flsl(unsigned long x) ... you switch to always_inline here? (replying out of order) > --- a/xen/arch/arm/include/asm/arm32/bitops.h > +++ b/xen/arch/arm/include/asm/arm32/bitops.h > @@ -1,7 +1,7 @@ > #ifndef _ARM_ARM32_BITOPS_H > #define _ARM_ARM32_BITOPS_H > > -#define flsl fls > +#define arch_flsl fls It's the Arm maintainers to ultimately judge, but I'd be inclined to suggest #define arch_flsl arch_fls instead. That's not only behaviorally closer to what was there before, but also reduces (a tiny bit) the amount of work the compiler needs to carry out. Jan
[PATCH v9 03/15] xen/bitops: implement fls{l}() in common logic
To avoid the compilation error below, it is needed to update to places
in common/page_alloc.c where flsl() is used as now flsl() returns unsigned int:
./include/xen/kernel.h:18:21: error: comparison of distinct pointer types lacks
a cast [-Werror]
18 | (void) (&_x == &_y);\
| ^~
common/page_alloc.c:1843:34: note: in expansion of macro 'min'
1843 | unsigned int inc_order = min(MAX_ORDER, flsl(e - s) - 1);
generic_fls{l} was used instead of __builtin_clz{l}(x) as if x is 0,
the result in undefined.
Signed-off-by: Oleksii Kurochko
---
The patch is almost independent from Andrew's patch series
(
https://lore.kernel.org/xen-devel/20240313172716.2325427-1-andrew.coop...@citrix.com/T/#t)
except test_fls() function which IMO can be merged as a separate patch after
Andrew's patch
will be fully ready.
---
Changes in V9:
- update return type of fls and flsl() to unsigned int to be aligned with other
bit ops.
- update places where return value of fls() and flsl() is compared with int.
- update the commit message.
---
Changes in V8:
- do proper rebase: back definition of fls{l} to the current patch.
- drop the changes which removed ffz() in PPC. it should be done not
in this patch.
- add a message after Signed-off.
---
Changes in V7:
- Code style fixes
---
Changes in V6:
- new patch for the patch series.
---
xen/arch/arm/include/asm/arm32/bitops.h | 2 +-
xen/arch/arm/include/asm/arm64/bitops.h | 6 ++
xen/arch/arm/include/asm/bitops.h | 7 ++-
xen/arch/ppc/include/asm/bitops.h | 3 ---
xen/arch/x86/include/asm/bitops.h | 6 --
xen/common/bitops.c | 22 ++
xen/common/page_alloc.c | 4 ++--
xen/include/xen/bitops.h| 24
8 files changed, 57 insertions(+), 17 deletions(-)
diff --git a/xen/arch/arm/include/asm/arm32/bitops.h
b/xen/arch/arm/include/asm/arm32/bitops.h
index d0309d47c1..5552d4e945 100644
--- a/xen/arch/arm/include/asm/arm32/bitops.h
+++ b/xen/arch/arm/include/asm/arm32/bitops.h
@@ -1,7 +1,7 @@
#ifndef _ARM_ARM32_BITOPS_H
#define _ARM_ARM32_BITOPS_H
-#define flsl fls
+#define arch_flsl fls
/*
* Little endian assembly bitops. nr = 0 -> byte 0 bit 0.
diff --git a/xen/arch/arm/include/asm/arm64/bitops.h
b/xen/arch/arm/include/asm/arm64/bitops.h
index 0efde29068..5f5d97faa0 100644
--- a/xen/arch/arm/include/asm/arm64/bitops.h
+++ b/xen/arch/arm/include/asm/arm64/bitops.h
@@ -22,17 +22,15 @@ static /*__*/always_inline unsigned long __ffs(unsigned
long word)
*/
#define ffz(x) __ffs(~(x))
-static inline int flsl(unsigned long x)
+static inline int arch_flsl(unsigned long x)
{
uint64_t ret;
-if (__builtin_constant_p(x))
- return generic_flsl(x);
-
asm("clz\t%0, %1" : "=r" (ret) : "r" (x));
return BITS_PER_LONG - ret;
}
+#define arch_flsl arch_flsl
/* Based on linux/include/asm-generic/bitops/find.h */
diff --git a/xen/arch/arm/include/asm/bitops.h
b/xen/arch/arm/include/asm/bitops.h
index 8e16335e76..860d6d4689 100644
--- a/xen/arch/arm/include/asm/bitops.h
+++ b/xen/arch/arm/include/asm/bitops.h
@@ -78,17 +78,14 @@ bool clear_mask16_timeout(uint16_t mask, volatile void *p,
* the clz instruction for much better code efficiency.
*/
-static inline int fls(unsigned int x)
+static inline int arch_fls(unsigned int x)
{
int ret;
-if (__builtin_constant_p(x))
- return generic_fls(x);
-
asm("clz\t%"__OP32"0, %"__OP32"1" : "=r" (ret) : "r" (x));
return 32 - ret;
}
-
+#define arch_fls arch_fls
#define arch_ffs(x) ({ unsigned int __t = (x); fls(ISOLATE_LSB(__t)); })
#define arch_ffsl(x) ({ unsigned long __t = (x); flsl(ISOLATE_LSB(__t)); })
diff --git a/xen/arch/ppc/include/asm/bitops.h
b/xen/arch/ppc/include/asm/bitops.h
index e2b6473c8c..ca308fd62b 100644
--- a/xen/arch/ppc/include/asm/bitops.h
+++ b/xen/arch/ppc/include/asm/bitops.h
@@ -119,9 +119,6 @@ static inline int test_and_set_bit(unsigned int nr,
volatile void *addr)
(volatile unsigned int *)addr + BITOP_WORD(nr)) != 0;
}
-#define flsl(x) generic_flsl(x)
-#define fls(x) generic_fls(x)
-
/* Based on linux/include/asm-generic/bitops/ffz.h */
/*
* ffz - find first zero in word.
diff --git a/xen/arch/x86/include/asm/bitops.h
b/xen/arch/x86/include/asm/bitops.h
index 23f09fdb7a..8f3d76fe44 100644
--- a/xen/arch/x86/include/asm/bitops.h
+++ b/xen/arch/x86/include/asm/bitops.h
@@ -425,7 +425,7 @@ static always_inline unsigned int arch_ffsl(unsigned long x)
*
* This is defined the same way as ffs.
*/
-static inline int flsl(unsigned long x)
+static always_inline int arch_flsl(unsigned long x)
{
long r;
@@ -435,8 +435,9 @@ static inline int flsl(unsigned long x)
"1:" : "=r" (r) : "rm" (x));
return (int)r+1;
}
+#define arch_flsl arch_flsl
-static inline int
