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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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db4e919d9a
On x86_64 we can do a u64 * u64 -> u128 widening multiply followed by a u128 / u64 -> u64 division to implement a sane version of mul_u64_u32_div(). Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
92 lines
2.0 KiB
C
92 lines
2.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_DIV64_H
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#define _ASM_X86_DIV64_H
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#ifdef CONFIG_X86_32
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#include <linux/types.h>
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#include <linux/log2.h>
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/*
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* do_div() is NOT a C function. It wants to return
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* two values (the quotient and the remainder), but
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* since that doesn't work very well in C, what it
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* does is:
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*
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* - modifies the 64-bit dividend _in_place_
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* - returns the 32-bit remainder
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*
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* This ends up being the most efficient "calling
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* convention" on x86.
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*/
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#define do_div(n, base) \
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({ \
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unsigned long __upper, __low, __high, __mod, __base; \
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__base = (base); \
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if (__builtin_constant_p(__base) && is_power_of_2(__base)) { \
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__mod = n & (__base - 1); \
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n >>= ilog2(__base); \
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} else { \
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asm("" : "=a" (__low), "=d" (__high) : "A" (n));\
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__upper = __high; \
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if (__high) { \
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__upper = __high % (__base); \
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__high = __high / (__base); \
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} \
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asm("divl %2" : "=a" (__low), "=d" (__mod) \
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: "rm" (__base), "0" (__low), "1" (__upper)); \
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asm("" : "=A" (n) : "a" (__low), "d" (__high)); \
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} \
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__mod; \
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})
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static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder)
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{
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union {
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u64 v64;
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u32 v32[2];
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} d = { dividend };
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u32 upper;
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upper = d.v32[1];
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d.v32[1] = 0;
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if (upper >= divisor) {
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d.v32[1] = upper / divisor;
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upper %= divisor;
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}
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asm ("divl %2" : "=a" (d.v32[0]), "=d" (*remainder) :
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"rm" (divisor), "0" (d.v32[0]), "1" (upper));
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return d.v64;
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}
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#define div_u64_rem div_u64_rem
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static inline u64 mul_u32_u32(u32 a, u32 b)
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{
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u32 high, low;
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asm ("mull %[b]" : "=a" (low), "=d" (high)
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: [a] "a" (a), [b] "rm" (b) );
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return low | ((u64)high) << 32;
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}
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#define mul_u32_u32 mul_u32_u32
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#else
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# include <asm-generic/div64.h>
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static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 div)
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{
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u64 q;
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asm ("mulq %2; divq %3" : "=a" (q)
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: "a" (a), "rm" ((u64)mul), "rm" ((u64)div)
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: "rdx");
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return q;
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}
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#define mul_u64_u32_div mul_u64_u32_div
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#endif /* CONFIG_X86_32 */
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#endif /* _ASM_X86_DIV64_H */
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