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/riscv/lib/memset.S | 115 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 115 insertions(+) create mode 100644 arch/riscv/lib/memset.S (limited to 'arch/riscv/lib/memset.S') diff --git a/arch/riscv/lib/memset.S b/arch/riscv/lib/memset.S new file mode 100644 index 000000000..da23b8347 --- /dev/null +++ b/arch/riscv/lib/memset.S @@ -0,0 +1,115 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (C) 2013 Regents of the University of California + */ + + +#include +#include + +/* void *memset(void *, int, size_t) */ +SYM_FUNC_START(__memset) + move t0, a0 /* Preserve return value */ + + /* Defer to byte-oriented fill for small sizes */ + sltiu a3, a2, 16 + bnez a3, 4f + + /* + * Round to nearest XLEN-aligned address + * greater than or equal to start address + */ + addi a3, t0, SZREG-1 + andi a3, a3, ~(SZREG-1) + beq a3, t0, 2f /* Skip if already aligned */ + /* Handle initial misalignment */ + sub a4, a3, t0 +1: + sb a1, 0(t0) + addi t0, t0, 1 + bltu t0, a3, 1b + sub a2, a2, a4 /* Update count */ + +2: /* Duff's device with 32 XLEN stores per iteration */ + /* Broadcast value into all bytes */ + andi a1, a1, 0xff + slli a3, a1, 8 + or a1, a3, a1 + slli a3, a1, 16 + or a1, a3, a1 +#ifdef CONFIG_64BIT + slli a3, a1, 32 + or a1, a3, a1 +#endif + + /* Calculate end address */ + andi a4, a2, ~(SZREG-1) + add a3, t0, a4 + + andi a4, a4, 31*SZREG /* Calculate remainder */ + beqz a4, 3f /* Shortcut if no remainder */ + neg a4, a4 + addi a4, a4, 32*SZREG /* Calculate initial offset */ + + /* Adjust start address with offset */ + sub t0, t0, a4 + + /* Jump into loop body */ + /* Assumes 32-bit instruction lengths */ + la a5, 3f +#ifdef CONFIG_64BIT + srli a4, a4, 1 +#endif + add a5, a5, a4 + jr a5 +3: + REG_S a1, 0(t0) + REG_S a1, SZREG(t0) + REG_S a1, 2*SZREG(t0) + REG_S a1, 3*SZREG(t0) + REG_S a1, 4*SZREG(t0) + REG_S a1, 5*SZREG(t0) + REG_S a1, 6*SZREG(t0) + REG_S a1, 7*SZREG(t0) + REG_S a1, 8*SZREG(t0) + REG_S a1, 9*SZREG(t0) + REG_S a1, 10*SZREG(t0) + REG_S a1, 11*SZREG(t0) + REG_S a1, 12*SZREG(t0) + REG_S a1, 13*SZREG(t0) + REG_S a1, 14*SZREG(t0) + REG_S a1, 15*SZREG(t0) + REG_S a1, 16*SZREG(t0) + REG_S a1, 17*SZREG(t0) + REG_S a1, 18*SZREG(t0) + REG_S a1, 19*SZREG(t0) + REG_S a1, 20*SZREG(t0) + REG_S a1, 21*SZREG(t0) + REG_S a1, 22*SZREG(t0) + REG_S a1, 23*SZREG(t0) + REG_S a1, 24*SZREG(t0) + REG_S a1, 25*SZREG(t0) + REG_S a1, 26*SZREG(t0) + REG_S a1, 27*SZREG(t0) + REG_S a1, 28*SZREG(t0) + REG_S a1, 29*SZREG(t0) + REG_S a1, 30*SZREG(t0) + REG_S a1, 31*SZREG(t0) + addi t0, t0, 32*SZREG + bltu t0, a3, 3b + andi a2, a2, SZREG-1 /* Update count */ + +4: + /* Handle trailing misalignment */ + beqz a2, 6f + add a3, t0, a2 +5: + sb a1, 0(t0) + addi t0, t0, 1 + bltu t0, a3, 5b +6: + ret +SYM_FUNC_END(__memset) +SYM_FUNC_ALIAS_WEAK(memset, __memset) +SYM_FUNC_ALIAS(__pi_memset, __memset) +SYM_FUNC_ALIAS(__pi___memset, __memset) -- cgit v1.3.1