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Date:   Mon, 11 Apr 2022 02:32:51 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Baoquan He <bhe@redhat.com>
Cc:     philip.li@intel.com, kernel test robot <lkp@intel.com>,
        akpm@linux-foundation.org, kbuild-all@lists.01.org,
        linux-kernel@vger.kernel.org, kexec@lists.infradead.org,
        hch@lst.de, yangtiezhu@loongson.cn, amit.kachhap@arm.com,
        linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk
Subject: Re: [PATCH v5 RESEND 1/3] vmcore: Convert copy_oldmem_page() to take
 an iov_iter
Message-ID: <YlOFQx5VyVn6uXb6@casper.infradead.org>
References: <20220408090636.560886-2-bhe@redhat.com>
 <202204082128.JKXXDGpa-lkp@intel.com>
 <YlDbJSy4AI3/cODr@MiWiFi-R3L-srv>
 <YlDlBQYr9ldLWpFz@casper.infradead.org>
 <YlN3GkuYunspGxnd@MiWiFi-R3L-srv>
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On Mon, Apr 11, 2022 at 08:32:26AM +0800, Baoquan He wrote:
> On 04/09/22 at 02:44am, Matthew Wilcox wrote:
> > On Sat, Apr 09, 2022 at 09:02:29AM +0800, Baoquan He wrote:
> > > I tried on x86_64 system, for the 1st step, I got this:
> > > 
> > > [ ~]# wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> > > /root/bin/make.cross: No such file or directory
> > 
> > ... I don't think we need to reproduce it to see the problem.
> > 
> > > > sparse warnings: (new ones prefixed by >>)
> > > > >> arch/sh/kernel/crash_dump.c:23:36: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected void const *addr @@     got void [noderef] __iomem * @@
> > > >    arch/sh/kernel/crash_dump.c:23:36: sparse:     expected void const *addr
> > > >    arch/sh/kernel/crash_dump.c:23:36: sparse:     got void [noderef] __iomem *
> > > > 
> > > > vim +23 arch/sh/kernel/crash_dump.c
> > > > 
> > > >     13	
> > > >     14	ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
> > > >     15				 size_t csize, unsigned long offset)
> > > >     16	{
> > > >     17		void  __iomem *vaddr;
> > > >     18	
> > > >     19		if (!csize)
> > > >     20			return 0;
> > > >     21	
> > > >     22		vaddr = ioremap(pfn << PAGE_SHIFT, PAGE_SIZE);
> > > >   > 23		csize = copy_to_iter(vaddr + offset, csize, iter);
> > 
> > Unlike other architectures, sh4 does this by calling ioremap().
> > That gives us an __iomem qualified pointer, which it then warns about
> > passing to copy_to_iter().
> > 
> > There are a bunch of hacky things we could do to fix it, but for such an
> > unmaintained arch as sh, I'm inclined to do nothing.  We're more likely
> > to break something while fixing the warning.  Someone who knows the arch
> > can figure out what to do properly.
> 
> Checked code, this can be fixed by casting away __iomem when feeding
> __iomem pointer into function which doesn't expect it. While seems the
> lkp failed me again.

Sure, that's one of the hacky ways.  But the important thing is that
the _current_ code has a warning.  LKP only sends a nastygram because
we changed the line.  If the current maintainers of the SH architecture
haven't been bothered to fix it, I don't see why we should.

> Subject: [PATCH] sh: cast away __iomem to remove sparse warning
> 
> This warning happened when __iomem pointer is passed into fucntion which
> does expect it. casting away the __iomem can fix it.
> 
> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
>  arch/sh/kernel/crash_dump.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/sh/kernel/crash_dump.c b/arch/sh/kernel/crash_dump.c
> index 19ce6a950aac..b45bb0b8a182 100644
> --- a/arch/sh/kernel/crash_dump.c
> +++ b/arch/sh/kernel/crash_dump.c
> @@ -20,7 +20,7 @@ ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
>  		return 0;
>  
>  	vaddr = ioremap(pfn << PAGE_SHIFT, PAGE_SIZE);
> -	csize = copy_to_iter(vaddr + offset, csize, iter);
> +	csize = copy_to_iter((void __force *)vaddr + offset, csize, iter);
>  	iounmap(vaddr);
>  
>  	return csize;
> -- 
> 2.34.1
> 
> Hi Philipp,
> 
> I executed 'mkdir -p /root/bin', then can continue the next steps.
> However, the building failed with below message. I cloned linus's tree
> into the testing system. Then add remote
> https://github.com/intel-lab-lkp/linux. Forgive my stupidity on this. If
> I can test above code, I can merge it into patch in a new version.
> Otherwise, I will leave it alone as willy suggested.
> 
> [root@dell-pem710-02 linux]# wget https://download.01.org/0day-ci/archive/20220408/202204082128.JKXXDGpa-lkp@intel.com/config
> --2022-04-10 19:54:15--  https://download.01.org/0day-ci/archive/20220408/202204082128.JKXXDGpa-lkp@intel.com/config
> Resolving download.01.org (download.01.org)... 2600:1408:20:c90::4b21, 2600:1408:20:c9b::4b21, 23.208.55.108
> Connecting to download.01.org (download.01.org)|2600:1408:20:c90::4b21|:443... failed: Network is unreachable.
> Connecting to download.01.org (download.01.org)|2600:1408:20:c9b::4b21|:443... failed: Network is unreachable.
> Connecting to download.01.org (download.01.org)|23.208.55.108|:443... connected.
> HTTP request sent, awaiting response... 200 OK
> Length: 122058 (119K) [application/octet-stream]
> Saving to: ‘config’
> 
> config                            100%[============================================================>] 119.20K   769KB/s    in 0.2s    
> 
> 2022-04-10 19:54:16 (769 KB/s) - ‘config’ saved [122058/122058]
> 
> [root@dell-pem710-02 linux]# mv config .config
> [root@dell-pem710-02 linux]# COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=sh SHELL=/bin/bash arch/sh/kernel/
> Compiler will be installed in /root/0day
> make --keep-going CONFIG_OF_ALL_DTBS=y CONFIG_DTC=y CROSS_COMPILE=/root/0day/gcc-9.3.0-nolibc/sh4-linux/bin/sh4-linux- --jobs=32 C=1 CF=-fdiagnostic-prefix -D__CHECK_ENDIAN__ O=build_dir ARCH=sh SHELL=/bin/bash arch/sh/kernel/
> make[1]: Entering directory '/root/linux/build_dir'
>   SYNC    include/config/auto.conf.cmd
> ***
> *** The source tree is not clean, please run 'make ARCH=sh mrproper'
> *** in /root/linux
> ***
> make[2]: *** [../Makefile:574: outputmakefile] Error 1
>   HOSTCC  scripts/basic/fixdep
> make[2]: Target 'syncconfig' not remade because of errors.
> make[1]: *** [/root/linux/Makefile:722: include/config/auto.conf.cmd] Error 2
> make[1]: Failed to remake makefile 'include/config/auto.conf.cmd'.
> make[1]: Failed to remake makefile 'include/config/auto.conf'.
> ***
> *** The source tree is not clean, please run 'make ARCH=sh mrproper'
> *** in /root/linux
> ***
> make[1]: *** [/root/linux/Makefile:574: outputmakefile] Error 1
>   SYSHDR  arch/sh/include/generated/uapi/asm/unistd_32.h
>   SYSTBL  arch/sh/include/generated/asm/syscall_table.h
> Error: kernelrelease not valid - run 'make prepare' to update it
>   HOSTCC  scripts/dtc/dtc.o
>   HOSTCC  scripts/dtc/flattree.o
>   HOSTCC  scripts/dtc/fstree.o
>   HOSTCC  scripts/dtc/data.o
>   HOSTCC  scripts/dtc/treesource.o
>   HOSTCC  scripts/dtc/livetree.o
>   HOSTCC  scripts/dtc/srcpos.o
>   HOSTCC  scripts/dtc/checks.o
>   HOSTCC  scripts/dtc/util.o
>   LEX     scripts/dtc/dtc-lexer.lex.c
>   YACC    scripts/dtc/dtc-parser.tab.[ch]
>   HOSTCC  scripts/dtc/libfdt/fdt.o
>   HOSTCC  scripts/dtc/libfdt/fdt_ro.o
>   HOSTCC  scripts/dtc/libfdt/fdt_sw.o
>   HOSTCC  scripts/dtc/libfdt/fdt_wip.o
>   HOSTCC  scripts/dtc/libfdt/fdt_rw.o
>   HOSTCC  scripts/dtc/libfdt/fdt_strerror.o
>   HOSTCC  scripts/dtc/libfdt/fdt_empty_tree.o
>   HOSTCC  scripts/dtc/libfdt/fdt_addresses.o
>   HOSTCC  scripts/dtc/libfdt/fdt_overlay.o
>   HOSTCC  scripts/dtc/fdtoverlay.o
>   HOSTCC  scripts/dtc/dtc-lexer.lex.o
>   HOSTCC  scripts/dtc/dtc-parser.tab.o
>   HOSTLD  scripts/dtc/fdtoverlay
>   HOSTLD  scripts/dtc/dtc
> make[1]: Target 'arch/sh/kernel/' not remade because of errors.
> make[1]: Leaving directory '/root/linux/build_dir'
> make: *** [Makefile:219: __sub-make] Error 2
> make: Target 'arch/sh/kernel/' not remade because of errors.
> [root@dell-pem710-02 linux]# 
> 
> 
> 
> > 
>