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/alpha/lib/strchr.S | 72 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 72 insertions(+) create mode 100644 arch/alpha/lib/strchr.S (limited to 'arch/alpha/lib/strchr.S') diff --git a/arch/alpha/lib/strchr.S b/arch/alpha/lib/strchr.S new file mode 100644 index 000000000..68c54ff50 --- /dev/null +++ b/arch/alpha/lib/strchr.S @@ -0,0 +1,72 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * arch/alpha/lib/strchr.S + * Contributed by Richard Henderson (rth@tamu.edu) + * + * Return the address of a given character within a null-terminated + * string, or null if it is not found. + */ +#include +#include + + .set noreorder + .set noat + + .align 3 + .globl strchr + .ent strchr +strchr: + .frame sp, 0, ra + .prologue 0 + + zapnot a1, 1, a1 # e0 : zero extend the search character + ldq_u t0, 0(a0) # .. e1 : load first quadword + sll a1, 8, t5 # e0 : replicate the search character + andnot a0, 7, v0 # .. e1 : align our loop pointer + or t5, a1, a1 # e0 : + lda t4, -1 # .. e1 : build garbage mask + sll a1, 16, t5 # e0 : + cmpbge zero, t0, t2 # .. e1 : bits set iff byte == zero + mskqh t4, a0, t4 # e0 : + or t5, a1, a1 # .. e1 : + sll a1, 32, t5 # e0 : + cmpbge zero, t4, t4 # .. e1 : bits set iff byte is garbage + or t5, a1, a1 # e0 : + xor t0, a1, t1 # .. e1 : make bytes == c zero + cmpbge zero, t1, t3 # e0 : bits set iff byte == c + or t2, t3, t0 # e1 : bits set iff char match or zero match + andnot t0, t4, t0 # e0 : clear garbage bits + bne t0, $found # .. e1 (zdb) + +$loop: ldq t0, 8(v0) # e0 : + addq v0, 8, v0 # .. e1 : + nop # e0 : + xor t0, a1, t1 # .. e1 (ev5 data stall) + cmpbge zero, t0, t2 # e0 : bits set iff byte == 0 + cmpbge zero, t1, t3 # .. e1 : bits set iff byte == c + or t2, t3, t0 # e0 : + beq t0, $loop # .. e1 (zdb) + +$found: negq t0, t1 # e0 : clear all but least set bit + and t0, t1, t0 # e1 (stall) + + and t0, t3, t1 # e0 : bit set iff byte was the char + beq t1, $retnull # .. e1 (zdb) + + and t0, 0xf0, t2 # e0 : binary search for that set bit + and t0, 0xcc, t3 # .. e1 : + and t0, 0xaa, t4 # e0 : + cmovne t2, 4, t2 # .. e1 : + cmovne t3, 2, t3 # e0 : + cmovne t4, 1, t4 # .. e1 : + addq t2, t3, t2 # e0 : + addq v0, t4, v0 # .. e1 : + addq v0, t2, v0 # e0 : + ret # .. e1 : + +$retnull: + mov zero, v0 # e0 : + ret # .. e1 : + + .end strchr + EXPORT_SYMBOL(strchr) -- cgit v1.3.1