From 119e9db233ad0f4cbd4cfb9f9385a7bca378b37d Mon Sep 17 00:00:00 2001 From: Zeng Chi Date: Mon, 21 Sep 2026 18:24:42 +0800 Subject: KVM: Don't pre-reserve xarray entries when storing empty/NULL attributes Skip the xarray reservation loop when clearing all memory attributes, as storing NULL only erases the entry and never needs to allocate, so no reservation (and no cleanup of a failed one) is required in that case. Suggested-by: Sean Christopherson Cc: David Ballesteros Signed-off-by: Zeng Chi Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com [sean: split to separate patch] Signed-off-by: Sean Christopherson --- arch/xtensa/lib/memset.S | 155 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 155 insertions(+) create mode 100644 arch/xtensa/lib/memset.S (limited to 'arch/xtensa/lib/memset.S') diff --git a/arch/xtensa/lib/memset.S b/arch/xtensa/lib/memset.S new file mode 100644 index 000000000..262c3f39f --- /dev/null +++ b/arch/xtensa/lib/memset.S @@ -0,0 +1,155 @@ +/* + * arch/xtensa/lib/memset.S + * + * ANSI C standard library function memset + * (Well, almost. .fixup code might return zero.) + * + * This file is subject to the terms and conditions of the GNU General + * Public License. See the file "COPYING" in the main directory of + * this archive for more details. + * + * Copyright (C) 2002 Tensilica Inc. + */ + +#include +#include +#include + +/* + * void *memset(void *dst, int c, size_t length) + * + * The algorithm is as follows: + * Create a word with c in all byte positions + * If the destination is aligned, + * do 16B chucks with a loop, and then finish up with + * 8B, 4B, 2B, and 1B stores conditional on the length. + * If destination is unaligned, align it by conditionally + * setting 1B and 2B and then go to aligned case. + * This code tries to use fall-through branches for the common + * case of an aligned destination (except for the branches to + * the alignment labels). + */ + +.text +ENTRY(__memset) +WEAK(memset) + + abi_entry_default + # a2/ dst, a3/ c, a4/ length + extui a3, a3, 0, 8 # mask to just 8 bits + slli a7, a3, 8 # duplicate character in all bytes of word + or a3, a3, a7 # ... + slli a7, a3, 16 # ... + or a3, a3, a7 # ... + mov a5, a2 # copy dst so that a2 is return value + movi a6, 3 # for alignment tests + bany a2, a6, .Ldstunaligned # if dst is unaligned +.L0: # return here from .Ldstunaligned when dst is aligned + srli a7, a4, 4 # number of loop iterations with 16B + # per iteration + bnez a4, .Laligned + abi_ret_default + +/* + * Destination is word-aligned. + */ + # set 16 bytes per iteration for word-aligned dst + .align 4 # 1 mod 4 alignment for LOOPNEZ + .byte 0 # (0 mod 4 alignment for LBEG) +.Laligned: +#if XCHAL_HAVE_LOOPS + loopnez a7, .Loop1done +#else /* !XCHAL_HAVE_LOOPS */ + beqz a7, .Loop1done + slli a6, a7, 4 + add a6, a6, a5 # a6 = end of last 16B chunk +#endif /* !XCHAL_HAVE_LOOPS */ +.Loop1: +EX(10f) s32i a3, a5, 0 +EX(10f) s32i a3, a5, 4 +EX(10f) s32i a3, a5, 8 +EX(10f) s32i a3, a5, 12 + addi a5, a5, 16 +#if !XCHAL_HAVE_LOOPS + blt a5, a6, .Loop1 +#endif /* !XCHAL_HAVE_LOOPS */ +.Loop1done: + bbci.l a4, 3, .L2 + # set 8 bytes +EX(10f) s32i a3, a5, 0 +EX(10f) s32i a3, a5, 4 + addi a5, a5, 8 +.L2: + bbci.l a4, 2, .L3 + # set 4 bytes +EX(10f) s32i a3, a5, 0 + addi a5, a5, 4 +.L3: + bbci.l a4, 1, .L4 + # set 2 bytes +EX(10f) s16i a3, a5, 0 + addi a5, a5, 2 +.L4: + bbci.l a4, 0, .L5 + # set 1 byte +EX(10f) s8i a3, a5, 0 +.L5: +.Lret1: + abi_ret_default + +/* + * Destination is unaligned + */ + +.Ldstunaligned: + bltui a4, 8, .Lbyteset # do short copies byte by byte + bbci.l a5, 0, .L20 # branch if dst alignment half-aligned + # dst is only byte aligned + # set 1 byte +EX(10f) s8i a3, a5, 0 + addi a5, a5, 1 + addi a4, a4, -1 + # now retest if dst aligned + bbci.l a5, 1, .L0 # if now aligned, return to main algorithm +.L20: + # dst half-aligned + # set 2 bytes +EX(10f) s16i a3, a5, 0 + addi a5, a5, 2 + addi a4, a4, -2 + j .L0 # dst is now aligned, return to main algorithm + +/* + * Byte by byte set + */ + .align 4 + .byte 0 # 1 mod 4 alignment for LOOPNEZ + # (0 mod 4 alignment for LBEG) +.Lbyteset: +#if XCHAL_HAVE_LOOPS + loopnez a4, .Lbytesetdone +#else /* !XCHAL_HAVE_LOOPS */ + beqz a4, .Lbytesetdone + add a6, a5, a4 # a6 = ending address +#endif /* !XCHAL_HAVE_LOOPS */ +.Lbyteloop: +EX(10f) s8i a3, a5, 0 + addi a5, a5, 1 +#if !XCHAL_HAVE_LOOPS + blt a5, a6, .Lbyteloop +#endif /* !XCHAL_HAVE_LOOPS */ +.Lbytesetdone: + abi_ret_default + +ENDPROC(__memset) +EXPORT_SYMBOL(__memset) +EXPORT_SYMBOL(memset) + + .section .fixup, "ax" + .align 4 + +/* We return zero if a failure occurred. */ + +10: + movi a2, 0 + abi_ret_default -- cgit v1.3.1