[PATCH v2] xen/lib: introduce generic find next bit operations

Oleksii Kurochko posted 1 patch 2 weeks, 2 days ago
Patches applied successfully (tree, apply log)
git fetch https://gitlab.com/xen-project/patchew/xen tags/patchew/fea2e65768457adcfedbfcc294004b1d5c2e86ea.1707495704.git.oleksii.kurochko@gmail.com
docs/misra/exclude-list.json                  |   8 +-
xen/arch/arm/arm64/lib/Makefile               |   2 +-
xen/arch/arm/include/asm/arm64/bitops.h       |  46 +------
xen/arch/ppc/include/asm/bitops.h             | 115 ------------------
xen/include/xen/bitops.h                      |  48 ++++++++
xen/lib/Makefile                              |   1 +
.../find_next_bit.c => lib/find-next-bit.c}   |   0
7 files changed, 55 insertions(+), 165 deletions(-)
rename xen/{arch/arm/arm64/lib/find_next_bit.c => lib/find-next-bit.c} (100%)
[PATCH v2] xen/lib: introduce generic find next bit operations
Posted by Oleksii Kurochko 2 weeks, 2 days ago
find-next-bit.c is common for Arm64, PPC and RISCV64,
so it is moved to xen/lib.

PPC has been transitioned to generic functions from find-next-bit.c
since it now shares the same implementation as the PPC-specific code.

The MISRA exclude list has been updated to verify
lib/find-next-bit.c instead of Arm's find_next_bit.c,
as Arm's find_next_bit.c has been relocated to xen/lib/.

Despite CONFIG_GENERIC_FIND_FIRST_BIT not currently being used in
Xen and being removed from the Linux kernel [1], it could theoretically
prove useful for Xen. This is because the Linux kernel transitioned
Arm to the generic version of find_first_bit() and
find_first_zero_bit() due to improvements [1] in both performance
and .text size.
It would be prudent to investigate whether [1] is applicable to Xen
as well and, if so, implement the necessary changes in a separate patch.

[1] https://lore.kernel.org/linux-arch/20211005054059.475634-5-yury.norov@gmail.com/

Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
---
 docs/misra/exclude-list.json                  |   8 +-
 xen/arch/arm/arm64/lib/Makefile               |   2 +-
 xen/arch/arm/include/asm/arm64/bitops.h       |  46 +------
 xen/arch/ppc/include/asm/bitops.h             | 115 ------------------
 xen/include/xen/bitops.h                      |  48 ++++++++
 xen/lib/Makefile                              |   1 +
 .../find_next_bit.c => lib/find-next-bit.c}   |   0
 7 files changed, 55 insertions(+), 165 deletions(-)
 rename xen/{arch/arm/arm64/lib/find_next_bit.c => lib/find-next-bit.c} (100%)

diff --git a/docs/misra/exclude-list.json b/docs/misra/exclude-list.json
index 7971d0e70f..b28174d0eb 100644
--- a/docs/misra/exclude-list.json
+++ b/docs/misra/exclude-list.json
@@ -13,10 +13,6 @@
             "rel_path": "arch/arm/arm64/insn.c",
             "comment": "Imported on Linux, ignore for now"
         },
-        {
-            "rel_path": "arch/arm/arm64/lib/find_next_bit.c",
-            "comment": "Imported from Linux, ignore for now"
-        },
         {
             "rel_path": "arch/x86/acpi/boot.c",
             "comment": "Imported from Linux, ignore for now"
@@ -221,6 +217,10 @@
             "rel_path": "include/xen/decompress.h",
             "comment": "Imported from Linux, ignore for now"
         },
+        {
+            "rel_path": "lib/find-next-bit.c",
+            "comment": "Imported from Linux, ignore for now"
+        },
         {
             "rel_path": "lib/list-sort.c",
             "comment": "Imported from Linux, ignore for now"
diff --git a/xen/arch/arm/arm64/lib/Makefile b/xen/arch/arm/arm64/lib/Makefile
index 1b9c7a95e6..66cfac435a 100644
--- a/xen/arch/arm/arm64/lib/Makefile
+++ b/xen/arch/arm/arm64/lib/Makefile
@@ -1,4 +1,4 @@
 obj-y += memcpy.o memcmp.o memmove.o memset.o memchr.o
 obj-y += clear_page.o
-obj-y += bitops.o find_next_bit.o
+obj-y += bitops.o
 obj-y += strchr.o strcmp.o strlen.o strncmp.o strnlen.o strrchr.o
diff --git a/xen/arch/arm/include/asm/arm64/bitops.h b/xen/arch/arm/include/asm/arm64/bitops.h
index d85a49bca4..0efde29068 100644
--- a/xen/arch/arm/include/asm/arm64/bitops.h
+++ b/xen/arch/arm/include/asm/arm64/bitops.h
@@ -36,57 +36,13 @@ static inline int flsl(unsigned long x)
 
 /* Based on linux/include/asm-generic/bitops/find.h */
 
-#ifndef find_next_bit
-/**
- * find_next_bit - find the next set bit in a memory region
- * @addr: The address to base the search on
- * @offset: The bitnumber to start searching at
- * @size: The bitmap size in bits
- */
-extern unsigned long find_next_bit(const unsigned long *addr, unsigned long
-		size, unsigned long offset);
-#endif
-
-#ifndef find_next_zero_bit
-/**
- * find_next_zero_bit - find the next cleared bit in a memory region
- * @addr: The address to base the search on
- * @offset: The bitnumber to start searching at
- * @size: The bitmap size in bits
- */
-extern unsigned long find_next_zero_bit(const unsigned long *addr, unsigned
-		long size, unsigned long offset);
-#endif
-
-#ifdef CONFIG_GENERIC_FIND_FIRST_BIT
-
-/**
- * find_first_bit - find the first set bit in a memory region
- * @addr: The address to start the search at
- * @size: The maximum size to search
- *
- * Returns the bit number of the first set bit.
- */
-extern unsigned long find_first_bit(const unsigned long *addr,
-				    unsigned long size);
-
-/**
- * find_first_zero_bit - find the first cleared bit in a memory region
- * @addr: The address to start the search at
- * @size: The maximum size to search
- *
- * Returns the bit number of the first cleared bit.
- */
-extern unsigned long find_first_zero_bit(const unsigned long *addr,
-					 unsigned long size);
-#else /* CONFIG_GENERIC_FIND_FIRST_BIT */
+#ifndef CONFIG_GENERIC_FIND_FIRST_BIT
 
 #define find_first_bit(addr, size) find_next_bit((addr), (size), 0)
 #define find_first_zero_bit(addr, size) find_next_zero_bit((addr), (size), 0)
 
 #endif /* CONFIG_GENERIC_FIND_FIRST_BIT */
 
-
 #endif /* _ARM_ARM64_BITOPS_H */
 /*
  * Local variables:
diff --git a/xen/arch/ppc/include/asm/bitops.h b/xen/arch/ppc/include/asm/bitops.h
index 5e7f36c21d..5820b9ce7b 100644
--- a/xen/arch/ppc/include/asm/bitops.h
+++ b/xen/arch/ppc/include/asm/bitops.h
@@ -217,119 +217,4 @@ static always_inline unsigned long __ffs(unsigned long word)
  */
 #define find_first_set_bit(x) (ffsl(x) - 1)
 
-/*
- * Find the first set bit in a memory region.
- */
-static inline unsigned long find_first_bit(const unsigned long *addr,
-                                           unsigned long size)
-{
-    const unsigned long *p = addr;
-    unsigned long result = 0;
-    unsigned long tmp;
-
-    while ( size & ~(BITS_PER_LONG - 1) )
-    {
-        if ( (tmp = *(p++)) )
-            goto found;
-        result += BITS_PER_LONG;
-        size -= BITS_PER_LONG;
-    }
-    if ( !size )
-        return result;
-
-    tmp = (*p) & (~0UL >> (BITS_PER_LONG - size));
-    if ( tmp == 0UL )         /* Are any bits set? */
-        return result + size; /* Nope. */
- found:
-    return result + __ffs(tmp);
-}
-
-static inline unsigned long find_next_bit(const unsigned long *addr,
-                                          unsigned long size,
-                                          unsigned long offset)
-{
-    const unsigned long *p = addr + BITOP_WORD(offset);
-    unsigned long result = offset & ~(BITS_PER_LONG - 1);
-    unsigned long tmp;
-
-    if ( offset >= size )
-        return size;
-    size -= result;
-    offset %= BITS_PER_LONG;
-    if ( offset )
-    {
-        tmp = *(p++);
-        tmp &= (~0UL << offset);
-        if ( size < BITS_PER_LONG )
-            goto found_first;
-        if ( tmp )
-            goto found_middle;
-        size -= BITS_PER_LONG;
-        result += BITS_PER_LONG;
-    }
-    while ( size & ~(BITS_PER_LONG - 1) )
-    {
-        if ( (tmp = *(p++)) )
-            goto found_middle;
-        result += BITS_PER_LONG;
-        size -= BITS_PER_LONG;
-    }
-    if ( !size )
-        return result;
-    tmp = *p;
-
- found_first:
-    tmp &= (~0UL >> (BITS_PER_LONG - size));
-    if ( tmp == 0UL )         /* Are any bits set? */
-        return result + size; /* Nope. */
- found_middle:
-    return result + __ffs(tmp);
-}
-
-/*
- * This implementation of find_{first,next}_zero_bit was stolen from
- * Linus' asm-alpha/bitops.h.
- */
-static inline unsigned long find_next_zero_bit(const unsigned long *addr,
-                                               unsigned long size,
-                                               unsigned long offset)
-{
-    const unsigned long *p = addr + BITOP_WORD(offset);
-    unsigned long result = offset & ~(BITS_PER_LONG - 1);
-    unsigned long tmp;
-
-    if ( offset >= size )
-        return size;
-    size -= result;
-    offset %= BITS_PER_LONG;
-    if ( offset )
-    {
-        tmp = *(p++);
-        tmp |= ~0UL >> (BITS_PER_LONG - offset);
-        if ( size < BITS_PER_LONG )
-            goto found_first;
-        if ( ~tmp )
-            goto found_middle;
-        size -= BITS_PER_LONG;
-        result += BITS_PER_LONG;
-    }
-    while ( size & ~(BITS_PER_LONG - 1) )
-    {
-        if ( ~(tmp = *(p++)) )
-            goto found_middle;
-        result += BITS_PER_LONG;
-        size -= BITS_PER_LONG;
-    }
-    if ( !size )
-        return result;
-    tmp = *p;
-
- found_first:
-    tmp |= ~0UL << size;
-    if ( tmp == ~0UL )        /* Are any bits zero? */
-        return result + size; /* Nope. */
- found_middle:
-    return result + ffz(tmp);
-}
-
 #endif /* _ASM_PPC_BITOPS_H */
diff --git a/xen/include/xen/bitops.h b/xen/include/xen/bitops.h
index 2cb7892bcc..e3c5a4ccf3 100644
--- a/xen/include/xen/bitops.h
+++ b/xen/include/xen/bitops.h
@@ -105,6 +105,54 @@ static inline int generic_flsl(unsigned long x)
  */
 #include <asm/bitops.h>
 
+#ifndef find_next_bit
+/**
+ * find_next_bit - find the next set bit in a memory region
+ * @addr: The address to base the search on
+ * @offset: The bitnumber to start searching at
+ * @size: The bitmap size in bits
+ */
+extern unsigned long find_next_bit(const unsigned long *addr,
+                                   unsigned long size,
+                                   unsigned long offset);
+#endif
+
+#ifndef find_next_zero_bit
+/**
+ * find_next_zero_bit - find the next cleared bit in a memory region
+ * @addr: The address to base the search on
+ * @offset: The bitnumber to start searching at
+ * @size: The bitmap size in bits
+ */
+extern unsigned long find_next_zero_bit(const unsigned long *addr,
+                                        unsigned long size,
+                                        unsigned long offset);
+#endif
+
+#ifndef find_first_bit
+/**
+ * find_first_bit - find the first set bit in a memory region
+ * @addr: The address to start the search at
+ * @size: The maximum size to search
+ *
+ * Returns the bit number of the first set bit.
+ */
+extern unsigned long find_first_bit(const unsigned long *addr,
+                                    unsigned long size);
+#endif
+
+#ifndef find_first_zero_bit
+/**
+ * find_first_zero_bit - find the first cleared bit in a memory region
+ * @addr: The address to start the search at
+ * @size: The maximum size to search
+ *
+ * Returns the bit number of the first cleared bit.
+ */
+extern unsigned long find_first_zero_bit(const unsigned long *addr,
+                                         unsigned long size);
+#endif
+
 #if BITS_PER_LONG == 64
 # define fls64 flsl
 # define ffs64 ffsl
diff --git a/xen/lib/Makefile b/xen/lib/Makefile
index 2d9ebb945f..e63798e1d4 100644
--- a/xen/lib/Makefile
+++ b/xen/lib/Makefile
@@ -3,6 +3,7 @@ obj-$(CONFIG_X86) += x86/
 lib-y += bsearch.o
 lib-y += ctors.o
 lib-y += ctype.o
+lib-y += find-next-bit.o
 lib-y += list-sort.o
 lib-y += memchr.o
 lib-y += memchr_inv.o
diff --git a/xen/arch/arm/arm64/lib/find_next_bit.c b/xen/lib/find-next-bit.c
similarity index 100%
rename from xen/arch/arm/arm64/lib/find_next_bit.c
rename to xen/lib/find-next-bit.c
-- 
2.43.0
Re: [PATCH v2] xen/lib: introduce generic find next bit operations
Posted by Oleksii 5 days, 19 hours ago
Hi Shawn,

Could you please take a look at the patch and PPC-related changes (
xen/arch/ppc/include/asm/bitops.h )?

Thanks in advance.

~ Oleksii

On Fri, 2024-02-09 at 18:58 +0100, Oleksii Kurochko wrote:
> find-next-bit.c is common for Arm64, PPC and RISCV64,
> so it is moved to xen/lib.
> 
> PPC has been transitioned to generic functions from find-next-bit.c
> since it now shares the same implementation as the PPC-specific code.
> 
> The MISRA exclude list has been updated to verify
> lib/find-next-bit.c instead of Arm's find_next_bit.c,
> as Arm's find_next_bit.c has been relocated to xen/lib/.
> 
> Despite CONFIG_GENERIC_FIND_FIRST_BIT not currently being used in
> Xen and being removed from the Linux kernel [1], it could
> theoretically
> prove useful for Xen. This is because the Linux kernel transitioned
> Arm to the generic version of find_first_bit() and
> find_first_zero_bit() due to improvements [1] in both performance
> and .text size.
> It would be prudent to investigate whether [1] is applicable to Xen
> as well and, if so, implement the necessary changes in a separate
> patch.
> 
> [1]
> https://lore.kernel.org/linux-arch/20211005054059.475634-5-yury.norov@gmail.com/
> 
> Suggested-by: Jan Beulich <jbeulich@suse.com>
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
> ---
>  docs/misra/exclude-list.json                  |   8 +-
>  xen/arch/arm/arm64/lib/Makefile               |   2 +-
>  xen/arch/arm/include/asm/arm64/bitops.h       |  46 +------
>  xen/arch/ppc/include/asm/bitops.h             | 115 ----------------
> --
>  xen/include/xen/bitops.h                      |  48 ++++++++
>  xen/lib/Makefile                              |   1 +
>  .../find_next_bit.c => lib/find-next-bit.c}   |   0
>  7 files changed, 55 insertions(+), 165 deletions(-)
>  rename xen/{arch/arm/arm64/lib/find_next_bit.c => lib/find-next-
> bit.c} (100%)
> 
> diff --git a/docs/misra/exclude-list.json b/docs/misra/exclude-
> list.json
> index 7971d0e70f..b28174d0eb 100644
> --- a/docs/misra/exclude-list.json
> +++ b/docs/misra/exclude-list.json
> @@ -13,10 +13,6 @@
>              "rel_path": "arch/arm/arm64/insn.c",
>              "comment": "Imported on Linux, ignore for now"
>          },
> -        {
> -            "rel_path": "arch/arm/arm64/lib/find_next_bit.c",
> -            "comment": "Imported from Linux, ignore for now"
> -        },
>          {
>              "rel_path": "arch/x86/acpi/boot.c",
>              "comment": "Imported from Linux, ignore for now"
> @@ -221,6 +217,10 @@
>              "rel_path": "include/xen/decompress.h",
>              "comment": "Imported from Linux, ignore for now"
>          },
> +        {
> +            "rel_path": "lib/find-next-bit.c",
> +            "comment": "Imported from Linux, ignore for now"
> +        },
>          {
>              "rel_path": "lib/list-sort.c",
>              "comment": "Imported from Linux, ignore for now"
> diff --git a/xen/arch/arm/arm64/lib/Makefile
> b/xen/arch/arm/arm64/lib/Makefile
> index 1b9c7a95e6..66cfac435a 100644
> --- a/xen/arch/arm/arm64/lib/Makefile
> +++ b/xen/arch/arm/arm64/lib/Makefile
> @@ -1,4 +1,4 @@
>  obj-y += memcpy.o memcmp.o memmove.o memset.o memchr.o
>  obj-y += clear_page.o
> -obj-y += bitops.o find_next_bit.o
> +obj-y += bitops.o
>  obj-y += strchr.o strcmp.o strlen.o strncmp.o strnlen.o strrchr.o
> diff --git a/xen/arch/arm/include/asm/arm64/bitops.h
> b/xen/arch/arm/include/asm/arm64/bitops.h
> index d85a49bca4..0efde29068 100644
> --- a/xen/arch/arm/include/asm/arm64/bitops.h
> +++ b/xen/arch/arm/include/asm/arm64/bitops.h
> @@ -36,57 +36,13 @@ static inline int flsl(unsigned long x)
>  
>  /* Based on linux/include/asm-generic/bitops/find.h */
>  
> -#ifndef find_next_bit
> -/**
> - * find_next_bit - find the next set bit in a memory region
> - * @addr: The address to base the search on
> - * @offset: The bitnumber to start searching at
> - * @size: The bitmap size in bits
> - */
> -extern unsigned long find_next_bit(const unsigned long *addr,
> unsigned long
> -		size, unsigned long offset);
> -#endif
> -
> -#ifndef find_next_zero_bit
> -/**
> - * find_next_zero_bit - find the next cleared bit in a memory region
> - * @addr: The address to base the search on
> - * @offset: The bitnumber to start searching at
> - * @size: The bitmap size in bits
> - */
> -extern unsigned long find_next_zero_bit(const unsigned long *addr,
> unsigned
> -		long size, unsigned long offset);
> -#endif
> -
> -#ifdef CONFIG_GENERIC_FIND_FIRST_BIT
> -
> -/**
> - * find_first_bit - find the first set bit in a memory region
> - * @addr: The address to start the search at
> - * @size: The maximum size to search
> - *
> - * Returns the bit number of the first set bit.
> - */
> -extern unsigned long find_first_bit(const unsigned long *addr,
> -				    unsigned long size);
> -
> -/**
> - * find_first_zero_bit - find the first cleared bit in a memory
> region
> - * @addr: The address to start the search at
> - * @size: The maximum size to search
> - *
> - * Returns the bit number of the first cleared bit.
> - */
> -extern unsigned long find_first_zero_bit(const unsigned long *addr,
> -					 unsigned long size);
> -#else /* CONFIG_GENERIC_FIND_FIRST_BIT */
> +#ifndef CONFIG_GENERIC_FIND_FIRST_BIT
>  
>  #define find_first_bit(addr, size) find_next_bit((addr), (size), 0)
>  #define find_first_zero_bit(addr, size) find_next_zero_bit((addr),
> (size), 0)
>  
>  #endif /* CONFIG_GENERIC_FIND_FIRST_BIT */
>  
> -
>  #endif /* _ARM_ARM64_BITOPS_H */
>  /*
>   * Local variables:
> diff --git a/xen/arch/ppc/include/asm/bitops.h
> b/xen/arch/ppc/include/asm/bitops.h
> index 5e7f36c21d..5820b9ce7b 100644
> --- a/xen/arch/ppc/include/asm/bitops.h
> +++ b/xen/arch/ppc/include/asm/bitops.h
> @@ -217,119 +217,4 @@ static always_inline unsigned long
> __ffs(unsigned long word)
>   */
>  #define find_first_set_bit(x) (ffsl(x) - 1)
>  
> -/*
> - * Find the first set bit in a memory region.
> - */
> -static inline unsigned long find_first_bit(const unsigned long
> *addr,
> -                                           unsigned long size)
> -{
> -    const unsigned long *p = addr;
> -    unsigned long result = 0;
> -    unsigned long tmp;
> -
> -    while ( size & ~(BITS_PER_LONG - 1) )
> -    {
> -        if ( (tmp = *(p++)) )
> -            goto found;
> -        result += BITS_PER_LONG;
> -        size -= BITS_PER_LONG;
> -    }
> -    if ( !size )
> -        return result;
> -
> -    tmp = (*p) & (~0UL >> (BITS_PER_LONG - size));
> -    if ( tmp == 0UL )         /* Are any bits set? */
> -        return result + size; /* Nope. */
> - found:
> -    return result + __ffs(tmp);
> -}
> -
> -static inline unsigned long find_next_bit(const unsigned long *addr,
> -                                          unsigned long size,
> -                                          unsigned long offset)
> -{
> -    const unsigned long *p = addr + BITOP_WORD(offset);
> -    unsigned long result = offset & ~(BITS_PER_LONG - 1);
> -    unsigned long tmp;
> -
> -    if ( offset >= size )
> -        return size;
> -    size -= result;
> -    offset %= BITS_PER_LONG;
> -    if ( offset )
> -    {
> -        tmp = *(p++);
> -        tmp &= (~0UL << offset);
> -        if ( size < BITS_PER_LONG )
> -            goto found_first;
> -        if ( tmp )
> -            goto found_middle;
> -        size -= BITS_PER_LONG;
> -        result += BITS_PER_LONG;
> -    }
> -    while ( size & ~(BITS_PER_LONG - 1) )
> -    {
> -        if ( (tmp = *(p++)) )
> -            goto found_middle;
> -        result += BITS_PER_LONG;
> -        size -= BITS_PER_LONG;
> -    }
> -    if ( !size )
> -        return result;
> -    tmp = *p;
> -
> - found_first:
> -    tmp &= (~0UL >> (BITS_PER_LONG - size));
> -    if ( tmp == 0UL )         /* Are any bits set? */
> -        return result + size; /* Nope. */
> - found_middle:
> -    return result + __ffs(tmp);
> -}
> -
> -/*
> - * This implementation of find_{first,next}_zero_bit was stolen from
> - * Linus' asm-alpha/bitops.h.
> - */
> -static inline unsigned long find_next_zero_bit(const unsigned long
> *addr,
> -                                               unsigned long size,
> -                                               unsigned long offset)
> -{
> -    const unsigned long *p = addr + BITOP_WORD(offset);
> -    unsigned long result = offset & ~(BITS_PER_LONG - 1);
> -    unsigned long tmp;
> -
> -    if ( offset >= size )
> -        return size;
> -    size -= result;
> -    offset %= BITS_PER_LONG;
> -    if ( offset )
> -    {
> -        tmp = *(p++);
> -        tmp |= ~0UL >> (BITS_PER_LONG - offset);
> -        if ( size < BITS_PER_LONG )
> -            goto found_first;
> -        if ( ~tmp )
> -            goto found_middle;
> -        size -= BITS_PER_LONG;
> -        result += BITS_PER_LONG;
> -    }
> -    while ( size & ~(BITS_PER_LONG - 1) )
> -    {
> -        if ( ~(tmp = *(p++)) )
> -            goto found_middle;
> -        result += BITS_PER_LONG;
> -        size -= BITS_PER_LONG;
> -    }
> -    if ( !size )
> -        return result;
> -    tmp = *p;
> -
> - found_first:
> -    tmp |= ~0UL << size;
> -    if ( tmp == ~0UL )        /* Are any bits zero? */
> -        return result + size; /* Nope. */
> - found_middle:
> -    return result + ffz(tmp);
> -}
> -
>  #endif /* _ASM_PPC_BITOPS_H */
> diff --git a/xen/include/xen/bitops.h b/xen/include/xen/bitops.h
> index 2cb7892bcc..e3c5a4ccf3 100644
> --- a/xen/include/xen/bitops.h
> +++ b/xen/include/xen/bitops.h
> @@ -105,6 +105,54 @@ static inline int generic_flsl(unsigned long x)
>   */
>  #include <asm/bitops.h>
>  
> +#ifndef find_next_bit
> +/**
> + * find_next_bit - find the next set bit in a memory region
> + * @addr: The address to base the search on
> + * @offset: The bitnumber to start searching at
> + * @size: The bitmap size in bits
> + */
> +extern unsigned long find_next_bit(const unsigned long *addr,
> +                                   unsigned long size,
> +                                   unsigned long offset);
> +#endif
> +
> +#ifndef find_next_zero_bit
> +/**
> + * find_next_zero_bit - find the next cleared bit in a memory region
> + * @addr: The address to base the search on
> + * @offset: The bitnumber to start searching at
> + * @size: The bitmap size in bits
> + */
> +extern unsigned long find_next_zero_bit(const unsigned long *addr,
> +                                        unsigned long size,
> +                                        unsigned long offset);
> +#endif
> +
> +#ifndef find_first_bit
> +/**
> + * find_first_bit - find the first set bit in a memory region
> + * @addr: The address to start the search at
> + * @size: The maximum size to search
> + *
> + * Returns the bit number of the first set bit.
> + */
> +extern unsigned long find_first_bit(const unsigned long *addr,
> +                                    unsigned long size);
> +#endif
> +
> +#ifndef find_first_zero_bit
> +/**
> + * find_first_zero_bit - find the first cleared bit in a memory
> region
> + * @addr: The address to start the search at
> + * @size: The maximum size to search
> + *
> + * Returns the bit number of the first cleared bit.
> + */
> +extern unsigned long find_first_zero_bit(const unsigned long *addr,
> +                                         unsigned long size);
> +#endif
> +
>  #if BITS_PER_LONG == 64
>  # define fls64 flsl
>  # define ffs64 ffsl
> diff --git a/xen/lib/Makefile b/xen/lib/Makefile
> index 2d9ebb945f..e63798e1d4 100644
> --- a/xen/lib/Makefile
> +++ b/xen/lib/Makefile
> @@ -3,6 +3,7 @@ obj-$(CONFIG_X86) += x86/
>  lib-y += bsearch.o
>  lib-y += ctors.o
>  lib-y += ctype.o
> +lib-y += find-next-bit.o
>  lib-y += list-sort.o
>  lib-y += memchr.o
>  lib-y += memchr_inv.o
> diff --git a/xen/arch/arm/arm64/lib/find_next_bit.c b/xen/lib/find-
> next-bit.c
> similarity index 100%
> rename from xen/arch/arm/arm64/lib/find_next_bit.c
> rename to xen/lib/find-next-bit.c

Re: [PATCH v2] xen/lib: introduce generic find next bit operations
Posted by Julien Grall 1 week, 5 days ago
Hi Oleksii,

On 09/02/2024 17:58, Oleksii Kurochko wrote:
> find-next-bit.c is common for Arm64, PPC and RISCV64,
> so it is moved to xen/lib.
> 
> PPC has been transitioned to generic functions from find-next-bit.c
> since it now shares the same implementation as the PPC-specific code.
> 
> The MISRA exclude list has been updated to verify
> lib/find-next-bit.c instead of Arm's find_next_bit.c,
> as Arm's find_next_bit.c has been relocated to xen/lib/.
> 
> Despite CONFIG_GENERIC_FIND_FIRST_BIT not currently being used in
> Xen and being removed from the Linux kernel [1], it could theoretically
> prove useful for Xen. This is because the Linux kernel transitioned
> Arm to the generic version of find_first_bit() and
> find_first_zero_bit() due to improvements [1] in both performance
> and .text size.
> It would be prudent to investigate whether [1] is applicable to Xen
> as well and, if so, implement the necessary changes in a separate patch.
> 
> [1] https://lore.kernel.org/linux-arch/20211005054059.475634-5-yury.norov@gmail.com/
> 
> Suggested-by: Jan Beulich <jbeulich@suse.com>
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>

Reviewed-by: Julien Grall <jgrall@amazon.com>

Cheers,

-- 
Julien Grall
Re: [PATCH v2] xen/lib: introduce generic find next bit operations
Posted by Oleksii 1 week, 5 days ago
Hi Julien,

On Tue, 2024-02-13 at 17:18 +0000, Julien Grall wrote:
> Hi Oleksii,
> 
> On 09/02/2024 17:58, Oleksii Kurochko wrote:
> > find-next-bit.c is common for Arm64, PPC and RISCV64,
> > so it is moved to xen/lib.
> > 
> > PPC has been transitioned to generic functions from find-next-bit.c
> > since it now shares the same implementation as the PPC-specific
> > code.
> > 
> > The MISRA exclude list has been updated to verify
> > lib/find-next-bit.c instead of Arm's find_next_bit.c,
> > as Arm's find_next_bit.c has been relocated to xen/lib/.
> > 
> > Despite CONFIG_GENERIC_FIND_FIRST_BIT not currently being used in
> > Xen and being removed from the Linux kernel [1], it could
> > theoretically
> > prove useful for Xen. This is because the Linux kernel transitioned
> > Arm to the generic version of find_first_bit() and
> > find_first_zero_bit() due to improvements [1] in both performance
> > and .text size.
> > It would be prudent to investigate whether [1] is applicable to Xen
> > as well and, if so, implement the necessary changes in a separate
> > patch.
> > 
> > [1]
> > https://lore.kernel.org/linux-arch/20211005054059.475634-5-yury.norov@gmail.com/
> > 
> > Suggested-by: Jan Beulich <jbeulich@suse.com>
> > Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
> 
> Reviewed-by: Julien Grall <jgrall@amazon.com>
Thanks for review.

~ Oleksii
Re: [PATCH v2] xen/lib: introduce generic find next bit operations
Posted by Jan Beulich 1 week, 6 days ago
On 09.02.2024 18:58, Oleksii Kurochko wrote:
> find-next-bit.c is common for Arm64, PPC and RISCV64,
> so it is moved to xen/lib.
> 
> PPC has been transitioned to generic functions from find-next-bit.c
> since it now shares the same implementation as the PPC-specific code.
> 
> The MISRA exclude list has been updated to verify
> lib/find-next-bit.c instead of Arm's find_next_bit.c,
> as Arm's find_next_bit.c has been relocated to xen/lib/.
> 
> Despite CONFIG_GENERIC_FIND_FIRST_BIT not currently being used in
> Xen and being removed from the Linux kernel [1], it could theoretically
> prove useful for Xen. This is because the Linux kernel transitioned
> Arm to the generic version of find_first_bit() and
> find_first_zero_bit() due to improvements [1] in both performance
> and .text size.
> It would be prudent to investigate whether [1] is applicable to Xen
> as well and, if so, implement the necessary changes in a separate patch.
> 
> [1] https://lore.kernel.org/linux-arch/20211005054059.475634-5-yury.norov@gmail.com/
> 
> Suggested-by: Jan Beulich <jbeulich@suse.com>
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>

A revision log would have been nice, though.

Jan
Re: [PATCH v2] xen/lib: introduce generic find next bit operations
Posted by Oleksii 1 week, 5 days ago
On Mon, 2024-02-12 at 15:15 +0100, Jan Beulich wrote:
> On 09.02.2024 18:58, Oleksii Kurochko wrote:
> > find-next-bit.c is common for Arm64, PPC and RISCV64,
> > so it is moved to xen/lib.
> > 
> > PPC has been transitioned to generic functions from find-next-bit.c
> > since it now shares the same implementation as the PPC-specific
> > code.
> > 
> > The MISRA exclude list has been updated to verify
> > lib/find-next-bit.c instead of Arm's find_next_bit.c,
> > as Arm's find_next_bit.c has been relocated to xen/lib/.
> > 
> > Despite CONFIG_GENERIC_FIND_FIRST_BIT not currently being used in
> > Xen and being removed from the Linux kernel [1], it could
> > theoretically
> > prove useful for Xen. This is because the Linux kernel transitioned
> > Arm to the generic version of find_first_bit() and
> > find_first_zero_bit() due to improvements [1] in both performance
> > and .text size.
> > It would be prudent to investigate whether [1] is applicable to Xen
> > as well and, if so, implement the necessary changes in a separate
> > patch.
> > 
> > [1]
> > https://lore.kernel.org/linux-arch/20211005054059.475634-5-yury.norov@gmail.com/
> > 
> > Suggested-by: Jan Beulich <jbeulich@suse.com>
> > Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
> 
> Reviewed-by: Jan Beulich <jbeulich@suse.com>
Thanks!

> 
> A revision log would have been nice, though.
Missed that. In case if it will be needed a new patch version, I'll
back the log.

~ Oleksii