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/x86/lib/getuser.S | 172 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 172 insertions(+) create mode 100644 arch/x86/lib/getuser.S (limited to 'arch/x86/lib/getuser.S') diff --git a/arch/x86/lib/getuser.S b/arch/x86/lib/getuser.S new file mode 100644 index 000000000..9d5654b8a --- /dev/null +++ b/arch/x86/lib/getuser.S @@ -0,0 +1,172 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * __get_user functions. + * + * (C) Copyright 1998 Linus Torvalds + * (C) Copyright 2005 Andi Kleen + * (C) Copyright 2008 Glauber Costa + * + * These functions have a non-standard call interface + * to make them more efficient, especially as they + * return an error value in addition to the "real" + * return value. + */ + +/* + * __get_user_X + * + * Inputs: %[r|e]ax contains the address. + * + * Outputs: %[r|e]ax is error code (0 or -EFAULT) + * %[r|e]dx contains zero-extended value + * %ecx contains the high half for 32-bit __get_user_8 + * + * + * These functions should not modify any other registers, + * as they get called from within inline assembly. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define ASM_BARRIER_NOSPEC ALTERNATIVE "", "lfence", X86_FEATURE_LFENCE_RDTSC + +.macro check_range size:req +.if IS_ENABLED(CONFIG_X86_64) + RUNTIME_CONST_PTR USER_PTR_MAX, rdx + cmp %rdx, %rax + cmova %rdx, %rax +.else + cmp $TASK_SIZE_MAX-\size+1, %eax + jae .Lbad_get_user + sbb %edx, %edx /* array_index_mask_nospec() */ + and %edx, %eax +.endif +.endm + +.macro UACCESS op src dst +1: \op \src,\dst + _ASM_EXTABLE_UA(1b, __get_user_handle_exception) +.endm + + + .text +SYM_FUNC_START(__get_user_1) + ANNOTATE_NOENDBR + check_range size=1 + ASM_STAC + UACCESS movzbl (%_ASM_AX),%edx + xor %eax,%eax + ASM_CLAC + RET +SYM_FUNC_END(__get_user_1) +EXPORT_SYMBOL(__get_user_1) + +SYM_FUNC_START(__get_user_2) + ANNOTATE_NOENDBR + check_range size=2 + ASM_STAC + UACCESS movzwl (%_ASM_AX),%edx + xor %eax,%eax + ASM_CLAC + RET +SYM_FUNC_END(__get_user_2) +EXPORT_SYMBOL(__get_user_2) + +SYM_FUNC_START(__get_user_4) + ANNOTATE_NOENDBR + check_range size=4 + ASM_STAC + UACCESS movl (%_ASM_AX),%edx + xor %eax,%eax + ASM_CLAC + RET +SYM_FUNC_END(__get_user_4) +EXPORT_SYMBOL(__get_user_4) + +SYM_FUNC_START(__get_user_8) + ANNOTATE_NOENDBR +#ifndef CONFIG_X86_64 + xor %ecx,%ecx +#endif + check_range size=8 + ASM_STAC +#ifdef CONFIG_X86_64 + UACCESS movq (%_ASM_AX),%rdx +#else + UACCESS movl (%_ASM_AX),%edx + UACCESS movl 4(%_ASM_AX),%ecx +#endif + xor %eax,%eax + ASM_CLAC + RET +SYM_FUNC_END(__get_user_8) +EXPORT_SYMBOL(__get_user_8) + +/* .. and the same for __get_user, just without the range checks */ +SYM_FUNC_START(__get_user_nocheck_1) + ANNOTATE_NOENDBR + ASM_STAC + ASM_BARRIER_NOSPEC + UACCESS movzbl (%_ASM_AX),%edx + xor %eax,%eax + ASM_CLAC + RET +SYM_FUNC_END(__get_user_nocheck_1) +EXPORT_SYMBOL(__get_user_nocheck_1) + +SYM_FUNC_START(__get_user_nocheck_2) + ANNOTATE_NOENDBR + ASM_STAC + ASM_BARRIER_NOSPEC + UACCESS movzwl (%_ASM_AX),%edx + xor %eax,%eax + ASM_CLAC + RET +SYM_FUNC_END(__get_user_nocheck_2) +EXPORT_SYMBOL(__get_user_nocheck_2) + +SYM_FUNC_START(__get_user_nocheck_4) + ANNOTATE_NOENDBR + ASM_STAC + ASM_BARRIER_NOSPEC + UACCESS movl (%_ASM_AX),%edx + xor %eax,%eax + ASM_CLAC + RET +SYM_FUNC_END(__get_user_nocheck_4) +EXPORT_SYMBOL(__get_user_nocheck_4) + +SYM_FUNC_START(__get_user_nocheck_8) + ANNOTATE_NOENDBR + ASM_STAC + ASM_BARRIER_NOSPEC +#ifdef CONFIG_X86_64 + UACCESS movq (%_ASM_AX),%rdx +#else + xor %ecx,%ecx + UACCESS movl (%_ASM_AX),%edx + UACCESS movl 4(%_ASM_AX),%ecx +#endif + xor %eax,%eax + ASM_CLAC + RET +SYM_FUNC_END(__get_user_nocheck_8) +EXPORT_SYMBOL(__get_user_nocheck_8) + + +SYM_CODE_START_LOCAL(__get_user_handle_exception) + ASM_CLAC +.Lbad_get_user: + xor %edx,%edx + mov $(-EFAULT),%_ASM_AX + RET +SYM_CODE_END(__get_user_handle_exception) -- cgit v1.3.1