From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELvJjGlq8oeoOv83AC4M+xeR+myYT6Eh6iaNnA6g5EnV+3KMgh6txV9yY3YFkk+7PlM0UDvL ARC-Seal: i=1; a=rsa-sha256; t=1520955636; cv=none; d=google.com; s=arc-20160816; b=JuP3RJEVAhk9vbZeKJjyRw7hTK+wMvAkW2+dUZCTCFNGddZLh9nPK45JgKWpscmg23 3DGVLornR4zTuj2CBX6cYy65Jad7k2kQK+6ct/e2fmCzP6EerDt+vi/9zYrPdT0uk+3j 0EzFlaLafldchfc9mfRxbnplXVsKq6XKtzrwUaTH3HETJDrin7Mr1ch05dRD+yxjM0ID hU81R53ZwEJQ3a2FlH+W6980YaUMShJbVps49JFJfLy84Oy81CjQNgc97MEFTiQ0I1X2 qVmeoerxi/818L4pa3qA7nuDRbnFK3T1cokOwTu6lRpRlVSdDKtTU5A79sFt7W4wQAqN AYDA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=+i8er+EEiu8gQyH0yUnHCad1OxVzffyy9fiibZminLE=; b=K/wNSAm+fIsr0vYAMAQOa8vimlmPpdUmXbEdDmlNxEUcjM3YGW1QV/IRht+wExVd1Y T3htfLj5YypI91KewX1lBuI9Vh62LuizW375jwn/oCr9E6yxqx8yp2FkDqHqZAlD4jat aKaqhtjvtwhlZCY0git+5Gl3IRZzE93Rjv3FTG0H8NQeCsfimXu1EJvubY1YAs9IOh4R T+NDMgyYn/jsP/Fg4hNiASBmqA50ieOiy21TlKW6shuRdSNDjX1ntttME4tsiWF+1sln Hrg9fv6pIMr43DX+ynFGu2ZLunknNmZCH8TORyQAV/Qo46J8jUhSa733mRrA3ltVt31l SG0w== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.71.90 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.71.90 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Denys Vlasenko , Dominik Brodowski , Andy Lutomirski , Arjan van de Ven , Borislav Petkov , Dan Williams , Dave Hansen , David Woodhouse , Josh Poimboeuf , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , Ingo Molnar Subject: [PATCH 4.14 118/140] x86/entry/64: Use xorl for faster register clearing Date: Tue, 13 Mar 2018 16:25:21 +0100 Message-Id: <20180313152506.118623579@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180313152458.201155692@linuxfoundation.org> References: <20180313152458.201155692@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1594836996970474110?= X-GMAIL-MSGID: =?utf-8?q?1594837577860023656?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dominik Brodowski commit ced5d0bf603fa0baee8ea889e1d70971fd210894 upstream. On some x86 CPU microarchitectures using 'xorq' to clear general-purpose registers is slower than 'xorl'. As 'xorl' is sufficient to clear all 64 bits of these registers due to zero-extension [*], switch the x86 64-bit entry code to use 'xorl'. No change in functionality and no change in code size. [*] According to Intel 64 and IA-32 Architecture Software Developer's Manual, section 3.4.1.1, the result of 32-bit operands are "zero- extended to a 64-bit result in the destination general-purpose register." The AMD64 Architecture Programmer’s Manual Volume 3, Appendix B.1, describes the same behaviour. Suggested-by: Denys Vlasenko Signed-off-by: Dominik Brodowski Cc: Andy Lutomirski Cc: Arjan van de Ven Cc: Borislav Petkov Cc: Dan Williams Cc: Dave Hansen Cc: David Woodhouse Cc: Greg Kroah-Hartman Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20180214175924.23065-3-linux@dominikbrodowski.net [ Improved on the changelog a bit. ] Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- arch/x86/entry/calling.h | 16 +++++------ arch/x86/entry/entry_64_compat.S | 54 +++++++++++++++++++-------------------- 2 files changed, 35 insertions(+), 35 deletions(-) --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -117,25 +117,25 @@ For 32-bit we have the following convent pushq %rcx /* pt_regs->cx */ pushq \rax /* pt_regs->ax */ pushq %r8 /* pt_regs->r8 */ - xorq %r8, %r8 /* nospec r8 */ + xorl %r8d, %r8d /* nospec r8 */ pushq %r9 /* pt_regs->r9 */ - xorq %r9, %r9 /* nospec r9 */ + xorl %r9d, %r9d /* nospec r9 */ pushq %r10 /* pt_regs->r10 */ - xorq %r10, %r10 /* nospec r10 */ + xorl %r10d, %r10d /* nospec r10 */ pushq %r11 /* pt_regs->r11 */ - xorq %r11, %r11 /* nospec r11*/ + xorl %r11d, %r11d /* nospec r11*/ pushq %rbx /* pt_regs->rbx */ xorl %ebx, %ebx /* nospec rbx*/ pushq %rbp /* pt_regs->rbp */ xorl %ebp, %ebp /* nospec rbp*/ pushq %r12 /* pt_regs->r12 */ - xorq %r12, %r12 /* nospec r12*/ + xorl %r12d, %r12d /* nospec r12*/ pushq %r13 /* pt_regs->r13 */ - xorq %r13, %r13 /* nospec r13*/ + xorl %r13d, %r13d /* nospec r13*/ pushq %r14 /* pt_regs->r14 */ - xorq %r14, %r14 /* nospec r14*/ + xorl %r14d, %r14d /* nospec r14*/ pushq %r15 /* pt_regs->r15 */ - xorq %r15, %r15 /* nospec r15*/ + xorl %r15d, %r15d /* nospec r15*/ UNWIND_HINT_REGS .if \save_ret pushq %rsi /* return address on top of stack */ --- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -85,25 +85,25 @@ ENTRY(entry_SYSENTER_compat) pushq %rcx /* pt_regs->cx */ pushq $-ENOSYS /* pt_regs->ax */ pushq $0 /* pt_regs->r8 = 0 */ - xorq %r8, %r8 /* nospec r8 */ + xorl %r8d, %r8d /* nospec r8 */ pushq $0 /* pt_regs->r9 = 0 */ - xorq %r9, %r9 /* nospec r9 */ + xorl %r9d, %r9d /* nospec r9 */ pushq $0 /* pt_regs->r10 = 0 */ - xorq %r10, %r10 /* nospec r10 */ + xorl %r10d, %r10d /* nospec r10 */ pushq $0 /* pt_regs->r11 = 0 */ - xorq %r11, %r11 /* nospec r11 */ + xorl %r11d, %r11d /* nospec r11 */ pushq %rbx /* pt_regs->rbx */ xorl %ebx, %ebx /* nospec rbx */ pushq %rbp /* pt_regs->rbp (will be overwritten) */ xorl %ebp, %ebp /* nospec rbp */ pushq $0 /* pt_regs->r12 = 0 */ - xorq %r12, %r12 /* nospec r12 */ + xorl %r12d, %r12d /* nospec r12 */ pushq $0 /* pt_regs->r13 = 0 */ - xorq %r13, %r13 /* nospec r13 */ + xorl %r13d, %r13d /* nospec r13 */ pushq $0 /* pt_regs->r14 = 0 */ - xorq %r14, %r14 /* nospec r14 */ + xorl %r14d, %r14d /* nospec r14 */ pushq $0 /* pt_regs->r15 = 0 */ - xorq %r15, %r15 /* nospec r15 */ + xorl %r15d, %r15d /* nospec r15 */ cld /* @@ -224,25 +224,25 @@ GLOBAL(entry_SYSCALL_compat_after_hwfram pushq %rbp /* pt_regs->cx (stashed in bp) */ pushq $-ENOSYS /* pt_regs->ax */ pushq $0 /* pt_regs->r8 = 0 */ - xorq %r8, %r8 /* nospec r8 */ + xorl %r8d, %r8d /* nospec r8 */ pushq $0 /* pt_regs->r9 = 0 */ - xorq %r9, %r9 /* nospec r9 */ + xorl %r9d, %r9d /* nospec r9 */ pushq $0 /* pt_regs->r10 = 0 */ - xorq %r10, %r10 /* nospec r10 */ + xorl %r10d, %r10d /* nospec r10 */ pushq $0 /* pt_regs->r11 = 0 */ - xorq %r11, %r11 /* nospec r11 */ + xorl %r11d, %r11d /* nospec r11 */ pushq %rbx /* pt_regs->rbx */ xorl %ebx, %ebx /* nospec rbx */ pushq %rbp /* pt_regs->rbp (will be overwritten) */ xorl %ebp, %ebp /* nospec rbp */ pushq $0 /* pt_regs->r12 = 0 */ - xorq %r12, %r12 /* nospec r12 */ + xorl %r12d, %r12d /* nospec r12 */ pushq $0 /* pt_regs->r13 = 0 */ - xorq %r13, %r13 /* nospec r13 */ + xorl %r13d, %r13d /* nospec r13 */ pushq $0 /* pt_regs->r14 = 0 */ - xorq %r14, %r14 /* nospec r14 */ + xorl %r14d, %r14d /* nospec r14 */ pushq $0 /* pt_regs->r15 = 0 */ - xorq %r15, %r15 /* nospec r15 */ + xorl %r15d, %r15d /* nospec r15 */ /* * User mode is traced as though IRQs are on, and SYSENTER @@ -298,9 +298,9 @@ sysret32_from_system_call: */ SWITCH_TO_USER_CR3_NOSTACK scratch_reg=%r8 scratch_reg2=%r9 - xorq %r8, %r8 - xorq %r9, %r9 - xorq %r10, %r10 + xorl %r8d, %r8d + xorl %r9d, %r9d + xorl %r10d, %r10d swapgs sysretl END(entry_SYSCALL_compat) @@ -358,25 +358,25 @@ ENTRY(entry_INT80_compat) pushq %rcx /* pt_regs->cx */ pushq $-ENOSYS /* pt_regs->ax */ pushq $0 /* pt_regs->r8 = 0 */ - xorq %r8, %r8 /* nospec r8 */ + xorl %r8d, %r8d /* nospec r8 */ pushq $0 /* pt_regs->r9 = 0 */ - xorq %r9, %r9 /* nospec r9 */ + xorl %r9d, %r9d /* nospec r9 */ pushq $0 /* pt_regs->r10 = 0 */ - xorq %r10, %r10 /* nospec r10 */ + xorl %r10d, %r10d /* nospec r10 */ pushq $0 /* pt_regs->r11 = 0 */ - xorq %r11, %r11 /* nospec r11 */ + xorl %r11d, %r11d /* nospec r11 */ pushq %rbx /* pt_regs->rbx */ xorl %ebx, %ebx /* nospec rbx */ pushq %rbp /* pt_regs->rbp */ xorl %ebp, %ebp /* nospec rbp */ pushq %r12 /* pt_regs->r12 */ - xorq %r12, %r12 /* nospec r12 */ + xorl %r12d, %r12d /* nospec r12 */ pushq %r13 /* pt_regs->r13 */ - xorq %r13, %r13 /* nospec r13 */ + xorl %r13d, %r13d /* nospec r13 */ pushq %r14 /* pt_regs->r14 */ - xorq %r14, %r14 /* nospec r14 */ + xorl %r14d, %r14d /* nospec r14 */ pushq %r15 /* pt_regs->r15 */ - xorq %r15, %r15 /* nospec r15 */ + xorl %r15d, %r15d /* nospec r15 */ cld /*