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From: Finn Thain <fthain@telegraphics.com.au>
To: Daniel Wagner <dwagner@suse.de>, Bart Van Assche <bvanassche@acm.org>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>,
	"James E. J. Bottomley" <jejb@linux.vnet.ibm.com>,
	linux-scsi@vger.kernel.org, Hannes Reinecke <hare@suse.de>,
	Arun Easi <aeasi@marvell.com>,
	Himanshu Madhani <himanshu.madhani@oracle.com>,
	Nilesh Javali <njavali@marvell.com>,
	Quinn Tran <qutran@marvell.com>, Martin Wilck <mwilck@suse.com>,
	Roman Bolshakov <r.bolshakov@yadro.com>
Subject: Re: [PATCH v7 15/15] qla2xxx: Fix endianness annotations in source files
Date: Sun, 24 May 2020 14:28:09 +1000 (AEST)
Message-ID: <alpine.LNX.2.22.394.2005211358460.8@nippy.intranet> (raw)
In-Reply-To: <20200520085652.ps64ccmgjefc46cc@beryllium.lan>

I went through commit 7ffa5b939751 ("scsi: qla2xxx: Fix endianness 
annotations in source files") and produced a new version without the 
'const' changes and without the new local variables. I also tweaked a few 
line breaks so that the line numbers did not change.

I then built the driver both with and without the patch:

mkdir /tmp/patched /tmp/unpatched
rm drivers/scsi/qla2xxx/built-in.a drivers/scsi/qla2xxx/*.o *.[is] 
make KBUILD_CFLAGS=-save-temps drivers/scsi/qla2xxx/built-in.a
mv *.s /tmp/patched/
git checkout @^
rm drivers/scsi/qla2xxx/built-in.a drivers/scsi/qla2xxx/*.o *.[is] 
make KBUILD_CFLAGS=-save-temps drivers/scsi/qla2xxx/built-in.a
mv *.s /tmp/unpatched/
meld /tmp/patched/ /tmp/unpatched/

This revealed some differences, in both x86_64 and i686 builds.

1. The wordsize changes in qla24xx_els_ct_entry() apparently prevented the 
compiler from emitting zero-extension mov (movzwl) instructions.

diff -ru /tmp/unpatched/qla_isr.s /tmp/patched/qla_isr.s
--- /tmp/unpatched/qla_isr.s    2020-05-24 13:59:04.327714528 +1000
+++ /tmp/patched/qla_isr.s      2020-05-24 13:56:58.437529886 +1000
@@ -8947,11 +8947,9 @@
        movw    %ax, -26(%rbp)
        movq    -104(%rbp), %rax
        movl    36(%rax), %eax
-       movzwl  %ax, %eax
        movl    %eax, -76(%rbp)
        movq    -104(%rbp), %rax
        movl    40(%rax), %eax
-       movzwl  %ax, %eax
        movl    %eax, -72(%rbp)
        cmpl    $83, -108(%rbp)
        jne     .L601
@@ -8991,8 +8989,7 @@
        movl    $458752, -12(%rbp)
 .L603:
        movq    -104(%rbp), %rax
-       movl    32(%rax), %eax
-       movzwl  %ax, %edi
+       movl    32(%rax), %edi
        movl    -72(%rbp), %esi
        movl    -76(%rbp), %ecx
        movzwl  -26(%rbp), %edx
(and so on.)

2. The get_unaligned_le32() changes produce new pointer offsets in the 
assembly code for qla82xx_get_table_desc() and qla82xx_get_data_desc().

diff -ru /tmp/unpatched/qla_target.s /tmp/patched/qla_target.s
--- /tmp/unpatched/qla_target.s 2020-05-24 14:02:32.178019380 +1000
+++ /tmp/patched/qla_target.s   2020-05-24 14:01:43.487947966 +1000
@@ -12884,10 +12884,10 @@
        .cfi_offset 6, -16
        movq    %rsp, %rbp
        .cfi_def_cfa_register 6
-       subq    $32, %rsp
-       movq    %rdi, -24(%rbp)
-       movq    %rsi, -32(%rbp)
-       movq    -32(%rbp), %rax
+       subq    $64, %rsp
+       movq    %rdi, -56(%rbp)
+       movq    %rsi, -64(%rbp)
+       movq    -64(%rbp), %rax
        movl    52(%rax), %eax
        movl    %eax, -8(%rbp)
        movl    $24, -12(%rbp)
@@ -12895,62 +12895,62 @@
        cmpl    %eax, -12(%rbp)
        cmovbe  -12(%rbp), %eax
        movl    %eax, %edx
-       movq    -32(%rbp), %rax
+       movq    -64(%rbp), %rax
        movl    %edx, 52(%rax)
-       movq    -24(%rbp), %rax
+       movq    -56(%rbp), %rax
(and so on.)

Was this expected? I find it surprising...

FWIW, I think that the .s files could have been validated automatically 
had the changes in the patch been confined to annotations.

  reply index

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-18 21:16 [PATCH v7 00/15] Fix qla2xxx endianness annotations Bart Van Assche
2020-05-18 21:16 ` [PATCH v7 01/15] qla2xxx: Fix spelling of a variable name Bart Van Assche
2020-05-18 21:16 ` [PATCH v7 02/15] qla2xxx: Suppress two recently introduced compiler warnings Bart Van Assche
2020-05-18 21:17 ` [PATCH v7 03/15] qla2xxx: Simplify the functions for dumping firmware Bart Van Assche
2020-05-18 21:17 ` [PATCH v7 04/15] qla2xxx: Sort BUILD_BUG_ON() statements alphabetically Bart Van Assche
2020-05-18 21:17 ` [PATCH v7 05/15] qla2xxx: Add more BUILD_BUG_ON() statements Bart Van Assche
2020-05-18 21:17 ` [PATCH v7 06/15] qla2xxx: Make a gap in struct qla2xxx_offld_chain explicit Bart Van Assche
2020-05-18 21:17 ` [PATCH v7 07/15] qla2xxx: Increase the size of struct qla_fcp_prio_cfg to FCP_PRIO_CFG_SIZE Bart Van Assche
2020-05-18 21:17 ` [PATCH v7 08/15] qla2xxx: Change two hardcoded constants into offsetof() / sizeof() expressions Bart Van Assche
2020-05-18 21:17 ` [PATCH v7 09/15] qla2xxx: Use register names instead of register offsets Bart Van Assche
2020-05-18 21:17 ` [PATCH v7 10/15] qla2xxx: Fix the code that reads from mailbox registers Bart Van Assche
2020-05-18 21:17 ` [PATCH v7 11/15] qla2xxx: Change {RD,WRT}_REG_*() function names from upper case into lower case Bart Van Assche
2020-05-18 21:17 ` [PATCH v7 12/15] qla2xxx: Cast explicitly to uint16_t / uint32_t Bart Van Assche
2020-05-19 15:29   ` Daniel Wagner
2020-05-18 21:17 ` [PATCH v7 13/15] qla2xxx: Use make_handle() instead of open-coding it Bart Van Assche
2020-05-18 21:17 ` [PATCH v7 14/15] qla2xxx: Fix endianness annotations in header files Bart Van Assche
2020-05-18 21:17 ` [PATCH v7 15/15] qla2xxx: Fix endianness annotations in source files Bart Van Assche
2020-05-19 15:24   ` Daniel Wagner
2020-05-20  7:39     ` Finn Thain
2020-05-20  8:56       ` Daniel Wagner
2020-05-24  4:28         ` Finn Thain [this message]
2020-05-24 15:50           ` Bart Van Assche
2020-05-24 23:45             ` Finn Thain
2020-05-20  2:30 ` [PATCH v7 00/15] Fix qla2xxx endianness annotations Martin K. Petersen

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