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| author | Zeng Chi <zengchi@kylinos.cn> | 2026-09-21 18:24:42 +0800 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2026-09-22 08:36:16 -0700 |
| commit | 119e9db233ad0f4cbd4cfb9f9385a7bca378b37d (patch) | |
| tree | 660d50d4139cb750fbde1ae3432452c20726c99d /arch/alpha/lib/ev67-strlen.S | |
| download | linux-stable-119e9db233ad0f4cbd4cfb9f9385a7bca378b37d.tar.gz linux-stable-119e9db233ad0f4cbd4cfb9f9385a7bca378b37d.zip | |
KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted
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 <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'arch/alpha/lib/ev67-strlen.S')
| -rw-r--r-- | arch/alpha/lib/ev67-strlen.S | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/arch/alpha/lib/ev67-strlen.S b/arch/alpha/lib/ev67-strlen.S new file mode 100644 index 000000000..3d9078807 --- /dev/null +++ b/arch/alpha/lib/ev67-strlen.S @@ -0,0 +1,51 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * arch/alpha/lib/ev67-strlen.S + * 21264 version by Rick Gorton <rick.gorton@alpha-processor.com> + * + * Finds length of a 0-terminated string. Optimized for the + * Alpha architecture: + * + * - memory accessed as aligned quadwords only + * - uses bcmpge to compare 8 bytes in parallel + * + * Much of the information about 21264 scheduling/coding comes from: + * Compiler Writer's Guide for the Alpha 21264 + * abbreviated as 'CWG' in other comments here + * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html + * Scheduling notation: + * E - either cluster + * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1 + * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1 + */ +#include <linux/export.h> + .set noreorder + .set noat + + .globl strlen + .ent strlen + .align 4 +strlen: + ldq_u $1, 0($16) # L : load first quadword ($16 may be misaligned) + lda $2, -1($31) # E : + insqh $2, $16, $2 # U : + andnot $16, 7, $0 # E : + + or $2, $1, $1 # E : + cmpbge $31, $1, $2 # E : $2 <- bitmask: bit i == 1 <==> i-th byte == 0 + nop # E : + bne $2, $found # U : + +$loop: ldq $1, 8($0) # L : + addq $0, 8, $0 # E : addr += 8 + cmpbge $31, $1, $2 # E : + beq $2, $loop # U : + +$found: + cttz $2, $3 # U0 : + addq $0, $3, $0 # E : + subq $0, $16, $0 # E : + ret $31, ($26) # L0 : + + .end strlen + EXPORT_SYMBOL(strlen) |