From: Martin Wilck <mwilck@suse.com>
To: Juergen Gross <jgross@suse.com>,
linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org
Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
stable@vger.kernel.org
Subject: Re: [PATCH] scsi: Let scsi_execute_cmd() mark args->sshdr as invalid
Date: Thu, 11 May 2023 15:23:14 +0200 [thread overview]
Message-ID: <e7c5f4334ab6ff897547c68ea216fbcba22d4929.camel@suse.com> (raw)
In-Reply-To: <85a7dc28-74ec-f4d6-b5c3-ca456ce9d380@suse.com>
On Thu, 2023-05-11 at 15:17 +0200, Juergen Gross wrote:
> >
> > We know for certain that sizeof(*sshdr) is 8 bytes, and will most
> > probably remain so. Thus
> >
> > memset(sshdr, 0, sizeof(*sshdr))
> >
> > would result in more efficient code.
>
> I fail to see why zeroing a single byte would be less efficient than
> zeroing
> a possibly unaligned 8-byte area.
I don't think it can be unaligned. gcc seems to think the same. It
compiles the memset(sshdr, ...) in scsi_normalize_sense() into a single
instruction on x86_64.
0xffffffff8177e9d0 <scsi_normalize_sense>: nopl 0x0(%rax,%rax,1) [FTRACE NOP]
0xffffffff8177e9d5 <scsi_normalize_sense+5>: test %rdi,%rdi
0xffffffff8177e9d8 <scsi_normalize_sense+8>: movq $0x0,(%rdx)
Martin
next prev parent reply other threads:[~2023-05-11 13:25 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-11 12:34 [PATCH] scsi: Let scsi_execute_cmd() mark args->sshdr as invalid Juergen Gross
2023-05-11 12:49 ` Bart Van Assche
2023-05-11 12:54 ` Juergen Gross
2023-05-11 13:10 ` Martin Wilck
2023-05-11 13:17 ` Juergen Gross
2023-05-11 13:23 ` Martin Wilck [this message]
2023-05-11 13:32 ` Juergen Gross
2023-05-11 15:59 ` Martin Wilck
2023-05-11 16:00 ` Martin Wilck
2023-05-17 2:06 ` Martin K. Petersen
2023-05-17 4:54 ` Juergen Gross
2023-05-17 15:05 ` John Garry
2023-05-18 4:53 ` Juergen Gross
2023-05-18 10:57 ` John Garry
2023-05-18 19:54 ` Bart Van Assche
2023-05-19 16:06 ` John Garry
2023-05-19 16:54 ` Bart Van Assche
2023-05-19 17:12 ` John Garry
2023-05-19 17:39 ` Bart Van Assche
2023-05-22 9:55 ` John Garry
2023-05-22 13:31 ` Bart Van Assche
2023-05-22 15:54 ` John Garry
2023-05-22 22:48 ` michael.christie
2023-05-21 1:19 ` Martin K. Petersen
2023-05-21 5:23 ` Juergen Gross
2023-05-22 22:26 ` Martin K. Petersen
2023-05-23 15:04 ` Mike Christie
2023-05-21 0:46 ` Martin K. Petersen
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