Re: [PATCH v5 RESEND 1/3] vmcore: Convert copy_oldmem_page() to take an iov_iter

[Baoquan He]

On 04/11/22 at 02:32am, Matthew Wilcox wrote:
> 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.

Agree, it's an already existed drawback. Then I will leave it as is.

> 
> > 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@xxxxxxxxxx>
> > ---
> >  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@xxxxxxxxx/config
> > --2022-04-10 19:54:15--  https://download.01.org/0day-ci/archive/20220408/202204082128.JKXXDGpa-lkp@xxxxxxxxx/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]# 
> > 
> > 
> > 
> > > 
> > 
>