[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v2 4/8] xen/ppc: Implement bitops.h
On 8/29/23 8:59 AM, Jan Beulich wrote: > On 23.08.2023 22:07, Shawn Anastasio wrote: >> Implement bitops.h, based on Linux's implementation as of commit >> 5321d1b1afb9a17302c6cec79f0cbf823eb0d3fc. Though it is based off of >> Linux's implementation, this code diverges significantly in a number of >> ways: >> - Bitmap entries changed to 32-bit words to match X86 and Arm on Xen >> - PPC32-specific code paths dropped >> - Formatting completely re-done to more closely line up with Xen. >> Including 4 space indentation. > > With this goal, ... > >> --- a/xen/arch/ppc/include/asm/bitops.h >> +++ b/xen/arch/ppc/include/asm/bitops.h >> @@ -1,9 +1,335 @@ >> +/* SPDX-License-Identifier: GPL-2.0-or-later */ >> +/* >> + * Adapted from Linux's arch/powerpc/include/asm/bitops.h. >> + * >> + * Merged version by David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>. >> + * Based on ppc64 versions by: Dave Engebretsen, Todd Inglett, Don >> + * Reed, Pat McCarthy, Peter Bergner, Anton Blanchard. They >> + * originally took it from the ppc32 code. >> + */ >> #ifndef _ASM_PPC_BITOPS_H >> #define _ASM_PPC_BITOPS_H >> >> +#include <asm/memory.h> >> + >> +#define __set_bit(n,p) set_bit(n,p) >> +#define __clear_bit(n,p) clear_bit(n,p) > > ... you want to add blanks after the commas as well. (You might also > simply omit parameters altogether.) > >> +#define BITOP_BITS_PER_WORD 32 >> +#define BITOP_MASK(nr) (1UL << ((nr) % BITOP_BITS_PER_WORD)) >> +#define BITOP_WORD(nr) ((nr) / BITOP_BITS_PER_WORD) >> +#define BITS_PER_BYTE 8 >> + >> /* PPC bit number conversion */ >> -#define PPC_BITLSHIFT(be) (BITS_PER_LONG - 1 - (be)) >> -#define PPC_BIT(bit) (1UL << PPC_BITLSHIFT(bit)) >> -#define PPC_BITMASK(bs, be) ((PPC_BIT(bs) - PPC_BIT(be)) | PPC_BIT(bs)) >> +#define PPC_BITLSHIFT(be) (BITS_PER_LONG - 1 - (be)) >> +#define PPC_BIT(bit) (1UL << PPC_BITLSHIFT(bit)) >> +#define PPC_BITMASK(bs, be) ((PPC_BIT(bs) - PPC_BIT(be)) | PPC_BIT(bs)) >> + >> +/* Macro for generating the ***_bits() functions */ >> +#define DEFINE_BITOP(fn, op, prefix) >> \ >> +static inline void fn(unsigned long mask, >> \ >> + volatile unsigned int *_p) >> \ > > Nit: Style. Either > > static inline void fn(unsigned long mask, > \ > volatile unsigned int *_p) > \ > > or > > static inline void fn(unsigned long mask, > \ > volatile unsigned int *_p) > \ > > . Also there's again an underscore-prefixed identifier here. > Will fix both. >> +{ >> \ >> + unsigned long old; >> \ >> + unsigned int *p = (unsigned int *)_p; >> \ >> + asm volatile ( >> \ >> + prefix >> \ >> +"1: lwarx %0,0,%3,0\n" >> \ >> + #op "%I2 %0,%0,%2\n" >> \ >> + "stwcx. %0,0,%3\n" >> \ >> + "bne- 1b\n" >> \ >> + : "=&r" (old), "+m" (*p) >> \ >> + : "rK" (mask), "r" (p) >> \ >> + : "cc", "memory"); >> \ > > The asm() body wants indenting by another four blanks (more instances below). > If I were to match the style used in the previous patch's atomic.h, the body should be indented to line up with the opening ( of the asm statement, right? I'll go ahead and do that for consistency's sake unless you think it would be better to just leave it as-is with an extra 4 spaces of indentation. >> +} >> + >> +DEFINE_BITOP(set_bits, or, "") >> +DEFINE_BITOP(change_bits, xor, "") >> + >> +#define DEFINE_CLROP(fn, prefix) >> \ >> +static inline void fn(unsigned long mask, volatile unsigned int *_p) >> \ >> +{ >> \ >> + unsigned long old; >> \ >> + unsigned int *p = (unsigned int *)_p; >> \ >> + asm volatile ( >> \ >> + prefix >> \ >> +"1: lwarx %0,0,%3,0\n" >> \ >> + "andc %0,%0,%2\n" >> \ >> + "stwcx. %0,0,%3\n" >> \ >> + "bne- 1b\n" >> \ >> + : "=&r" (old), "+m" (*p) >> \ >> + : "r" (mask), "r" (p) >> \ >> + : "cc", "memory"); >> \ >> +} >> + >> +DEFINE_CLROP(clear_bits, "") >> + >> +static inline void set_bit(int nr, volatile void *addr) >> +{ >> + set_bits(BITOP_MASK(nr), (volatile unsigned int *)addr + >> BITOP_WORD(nr)); >> +} >> +static inline void clear_bit(int nr, volatile void *addr) >> +{ >> + clear_bits(BITOP_MASK(nr), (volatile unsigned int *)addr + >> BITOP_WORD(nr)); >> +} >> + >> +/** >> + * test_bit - Determine whether a bit is set >> + * @nr: bit number to test >> + * @addr: Address to start counting from >> + */ >> +static inline int test_bit(int nr, const volatile void *addr) >> +{ >> + const volatile unsigned long *p = (const volatile unsigned long >> *)addr; >> + return 1UL & (p[BITOP_WORD(nr)] >> (nr & (BITOP_BITS_PER_WORD-1))); > > Nit: Too deep indentation. Plus blanks around - please. I also don't see > the need for the UL suffix, when the function returns int only (and really > means to return bool, I assume, but int is in line with x86 and Arm, I > expect). > Will fix the indentation and spacing around -. I'll also drop the UL suffix, but will keep the int return type, since as you guessed it's what Arm/x86 do. >> +} >> + >> +static inline unsigned long test_and_clear_bits(unsigned long mask, >> volatile void *_p) >> +{ >> + unsigned long old, t; >> + unsigned int *p = (unsigned int *)_p; >> + >> + asm volatile ( >> + PPC_ATOMIC_ENTRY_BARRIER >> + "1: lwarx %0,0,%3,0\n" >> + "andc %1,%0,%2\n" >> + "stwcx. %1,0,%3\n" >> + "bne- 1b\n" >> + PPC_ATOMIC_EXIT_BARRIER >> + : "=&r" (old), "=&r" (t) >> + : "r" (mask), "r" (p) >> + : "cc", "memory"); >> + >> + return (old & mask); >> +} >> + >> +static inline int test_and_clear_bit(unsigned int nr, >> + volatile void *addr) > > Nit: Too deep indentation again. > Will fix this and all subsequent occurrences. >> +DEFINE_TESTOP(test_and_set_bits, or, 0) >> + >> +static inline int test_and_set_bit(unsigned long nr, volatile void *addr) >> +{ >> + return test_and_set_bits(BITOP_MASK(nr), (volatile unsigned int *)addr >> + BITOP_WORD(nr)) != 0; > > Too long line. > Will fix. >> +} >> + >> +/** >> + * __test_and_set_bit - Set a bit and return its old value >> + * @nr: Bit to set >> + * @addr: Address to count from >> + * >> + * This operation is non-atomic and can be reordered. >> + * If two examples of this operation race, one can appear to succeed >> + * but actually fail. You must protect multiple accesses with a lock. >> + */ >> +static inline int __test_and_set_bit(int nr, volatile void *addr) >> +{ >> + unsigned int mask = BITOP_MASK(nr); >> + volatile unsigned int *p = >> + ((volatile unsigned int *)addr) + BITOP_WORD(nr); >> + unsigned int old = *p; >> + >> + *p = old | mask; >> + return (old & mask) != 0; >> +} >> + >> +/** >> + * __test_and_clear_bit - Clear a bit and return its old value >> + * @nr: Bit to clear >> + * @addr: Address to count from >> + * >> + * This operation is non-atomic and can be reordered. >> + * If two examples of this operation race, one can appear to succeed >> + * but actually fail. You must protect multiple accesses with a lock. >> + */ >> +static inline int __test_and_clear_bit(int nr, volatile void *addr) >> +{ >> + unsigned int mask = BITOP_MASK(nr); >> + volatile unsigned int *p = >> + ((volatile unsigned int *)addr) + BITOP_WORD(nr); >> + unsigned int old = *p; >> + >> + *p = old & ~mask; >> + return (old & mask) != 0; >> +} >> + >> +#define flsl(x) generic_flsl(x) >> +#define fls(x) generic_fls(x) >> +#define ffs(x) ({ unsigned int __t = (x); fls(__t & -__t); }) >> +#define ffsl(x) ({ unsigned long __t = (x); flsl(__t & -__t); }) > > Hmm, here you even have two underscores as prefixes. > Another carryover from Arm, sorry. Will fix. >> +/* Based on linux/include/asm-generic/bitops/ffz.h */ >> +/* >> + * ffz - find first zero in word. >> + * @word: The word to search >> + * >> + * Undefined if no zero exists, so code should check against ~0UL first. >> + */ >> +#define ffz(x) __ffs(~(x)) >> + >> +/** >> + * hweightN - returns the hamming weight of a N-bit word >> + * @x: the word to weigh >> + * >> + * The Hamming Weight of a number is the total number of bits set in it. >> + */ >> +#define hweight64(x) generic_hweight64(x) >> +#define hweight32(x) generic_hweight32(x) >> +#define hweight16(x) generic_hweight16(x) >> +#define hweight8(x) generic_hweight8(x) > > Not using popcnt{b,w,d}, e.g. via a compiler builtin? > Excellent point. It looks like gcc's __builtin_popcount* family of builtins will do what we want here. I suppose the other architectures in Xen don't do this because they target toolchains old enough to not have these builtins? >> +/* Based on linux/include/asm-generic/bitops/builtin-__ffs.h */ >> +/** >> + * __ffs - find first bit in word. >> + * @word: The word to search >> + * >> + * Undefined if no bit exists, so code should check against 0 first. >> + */ >> +static /*__*/always_inline unsigned long __ffs(unsigned long word) > > What's this odd comment about here? > (Yet another) carryover from Arm. Will fix. >> +{ >> + return __builtin_ctzl(word); >> +} >> + >> +/** >> + * find_first_set_bit - find the first set bit in @word >> + * @word: the word to search >> + * >> + * Returns the bit-number of the first set bit (first bit being 0). >> + * The input must *not* be zero. >> + */ >> +#define find_first_set_bit(x) ({ ffsl(x) - 1; }) > > Simply > > #define find_first_set_bit(x) (ffsl(x) - 1) > > without use of any extensions? > Good point, the extension usage here is obviously unnecessary. Will drop. >> +/* >> + * 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; > > Just using 4-blank indentation isn't enough to make this Xen style. > (More such elsewhere.) > Yes, fair enough. I'll reformat it. >> + tmp = (*p) & (~0UL >> (BITS_PER_LONG - size)); >> + if (tmp == 0UL) /* Are any bits set? */ >> + return result + size; /* Nope. */ >> +found: > > Labels indented by at least one blank please. (More elsewhere.) I wasn't aware of this style convention -- so a single blank before the label would be correct? I'll add that in, then. > Jan Thanks, Shawn
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