From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
mark.rutland@arm.com, dvyukov@google.com, seanjc@google.com,
pbonzini@redhat.com, mbenes@suse.cz
Subject: Re: [RFC][PATCH 21/22] x86,word-at-a-time: Remove .fixup usage
Date: Thu, 4 Nov 2021 16:33:10 -0700 [thread overview]
Message-ID: <20211104233310.2dg2gilae27l75a3@treble> (raw)
In-Reply-To: <20211104165525.767986267@infradead.org>
On Thu, Nov 04, 2021 at 05:47:50PM +0100, Peter Zijlstra wrote:
> XXX: I'm not really happy with this patch
>
> static inline unsigned long load_unaligned_zeropad(const void *addr)
> {
> - unsigned long ret, dummy;
> + unsigned long ret;
> +
> + asm("1:\tmov (%0),%0\n"
> + "2:\n"
> + _ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_LOAD_UNALIGNED, %0)
> + : "=&r" (ret)
> + : "0" ((unsigned long)addr));
>
> - asm(
> - "1:\tmov %2,%0\n"
> - "2:\n"
> - ".section .fixup,\"ax\"\n"
> - "3:\t"
> - "lea %2,%1\n\t"
> - "and %3,%1\n\t"
> - "mov (%1),%0\n\t"
> - "leal %2,%%ecx\n\t"
> - "andl %4,%%ecx\n\t"
> - "shll $3,%%ecx\n\t"
> - "shr %%cl,%0\n\t"
> - "jmp 2b\n"
> - ".previous\n"
> - _ASM_EXTABLE(1b, 3b)
> - :"=&r" (ret),"=&c" (dummy)
> - :"m" (*(unsigned long *)addr),
> - "i" (-sizeof(unsigned long)),
> - "i" (sizeof(unsigned long)-1));
> return ret;
> }
Yeah, it hurts code generation and I guess it's a hot path.
Maybe put the fixup code in the function. In case of
CONFIG_CC_HAS_ASM_GOTO_OUTPUT, it could be at a label at the end of the
function. Otherwise it'd have to be inline.
--
Josh
next prev parent reply other threads:[~2021-11-04 23:33 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-04 16:47 [RFC][PATCH 00/22] x86: Remove anonymous out-of-line fixups Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 01/22] bitfield.h: Fix "type of reg too small for mask" test Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 02/22] x86,mmx_32: Remove .fixup usage Peter Zijlstra
2021-11-04 18:00 ` Borislav Petkov
2021-11-05 11:20 ` David Laight
2021-11-04 20:22 ` Josh Poimboeuf
2021-11-05 8:05 ` Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 03/22] x86,copy_user_64: " Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 04/22] x86,copy_mc_64: " Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 05/22] x86,entry_64: " Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 06/22] x86,entry_32: " Peter Zijlstra
2021-11-04 20:39 ` Josh Poimboeuf
2021-11-05 7:43 ` Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 07/22] x86,extable: Extend extable functionality Peter Zijlstra
2021-11-04 21:49 ` Josh Poimboeuf
2021-11-05 7:54 ` Peter Zijlstra
2021-11-05 10:16 ` Mark Rutland
2021-11-05 17:32 ` Sean Christopherson
2021-11-05 18:45 ` Peter Zijlstra
2021-11-05 19:17 ` Sean Christopherson
2021-11-05 19:32 ` Peter Zijlstra
2021-11-05 19:47 ` Sean Christopherson
2021-11-05 20:15 ` Peter Zijlstra
2021-11-05 20:26 ` Peter Zijlstra
2021-11-05 22:30 ` Sean Christopherson
2021-11-04 16:47 ` [RFC][PATCH 08/22] x86,msr: Remove .fixup usage Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 09/22] x86,futex: " Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 10/22] x86,uaccess: " Peter Zijlstra
2021-11-04 22:28 ` Josh Poimboeuf
2021-11-04 16:47 ` [RFC][PATCH 11/22] x86,xen: " Peter Zijlstra
2021-11-04 22:31 ` Josh Poimboeuf
2021-11-05 7:56 ` Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 12/22] x86,fpu: " Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 13/22] x86,segment: " Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 14/22] x86,ftrace: " Peter Zijlstra
2021-11-04 22:35 ` Josh Poimboeuf
2021-11-05 7:57 ` Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 15/22] x86,vmx: " Peter Zijlstra
2021-11-04 18:50 ` Paolo Bonzini
2021-11-05 18:17 ` Sean Christopherson
2021-11-05 18:52 ` Peter Zijlstra
2021-11-05 20:58 ` Peter Zijlstra
2021-11-05 22:29 ` Sean Christopherson
2021-11-06 7:05 ` Paolo Bonzini
2021-11-06 8:36 ` Peter Zijlstra
2021-11-07 19:13 ` Paolo Bonzini
2021-11-06 8:28 ` Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 16/22] x86,checksum_32: " Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 17/22] x86,sgx: " Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 18/22] x86,kvm: " Peter Zijlstra
2021-11-04 18:50 ` Paolo Bonzini
2021-11-05 7:58 ` Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 19/22] x86,usercopy_32: Simplify Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 20/22] x86,usercopy: Remove .fixup usage Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 21/22] x86,word-at-a-time: " Peter Zijlstra
2021-11-04 23:33 ` Josh Poimboeuf [this message]
2021-11-05 8:04 ` Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 22/22] x86: Remove .fixup section Peter Zijlstra
2021-11-04 23:00 ` Josh Poimboeuf
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