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Date:   Wed, 12 Oct 2022 17:20:29 +0800
From:   Baoquan He <bhe@redhat.com>
To:     Niklas Schnelle <schnelle@linux.ibm.com>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        akpm@linux-foundation.org, hch@infradead.org,
        agordeev@linux.ibm.com, wangkefeng.wang@huawei.com,
        christophe.leroy@csgroup.eu, David.Laight@aculab.com,
        shorne@gmail.com, Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Sven Schnelle <svens@linux.ibm.com>, linux-s390@vger.kernel.org
Subject: Re: [PATCH v3 09/11] s390: mm: Convert to GENERIC_IOREMAP
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On 10/12/22 at 09:37am, Niklas Schnelle wrote:
> On Wed, 2022-10-12 at 13:52 +0800, Baoquan He wrote:
> > On 10/11/22 at 05:16pm, Niklas Schnelle wrote:
> > > On Sun, 2022-10-09 at 18:31 +0800, Baoquan He wrote:
> > > > By taking GENERIC_IOREMAP method, the generic ioremap_prot() and
> > > > iounmap() are visible and available to arch. Arch only needs to
> > > > provide implementation of arch_ioremap() or arch_iounmap() if there's
> > > > arch specific handling needed in its ioremap() or iounmap(). This
> > > > change will simplify implementation by removing duplicated codes with
> > > > generic ioremap() and iounmap(), and has the equivalent functioality
> > > > as before.
> > > > 
> > > > For s390, add hooks arch_ioremap() and arch_iounmap() for s390's special
> > > > operation when ioremap() and iounmap(), then ioremap_[wc|wt]() are
> > > > converted to use ioremap_prot() from GENERIC_IOREMAP.
> > > > 
> > > > Signed-off-by: Baoquan He <bhe@redhat.com>
> > > > Cc: Niklas Schnelle <schnelle@linux.ibm.com>
> > > > Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
> > > > Cc: Heiko Carstens <hca@linux.ibm.com>
> > > > Cc: Vasily Gorbik <gor@linux.ibm.com>
> > > > Cc: Alexander Gordeev <agordeev@linux.ibm.com>
> > > > Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
> > > > Cc: Sven Schnelle <svens@linux.ibm.com>
> > > > Cc: linux-s390@vger.kernel.org
> > > > ---
> > > > v2->v3:
> > > > - Add code comment inside arch_ioremap() to help uderstand the
> > > >   obsucre code. Christoph suggested this, Niklas provided the
> > > >   paragraph of text.
> > > > 
> > > >  arch/s390/Kconfig          |  1 +
> > > >  arch/s390/include/asm/io.h | 25 +++++++++------
> > > >  arch/s390/pci/pci.c        | 65 ++++++++------------------------------
> > > >  3 files changed, 30 insertions(+), 61 deletions(-)
> > > > 
> > > > diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> > > > index 318fce77601d..c59e1b25f59d 100644
> > > > --- a/arch/s390/Kconfig
> > > > +++ b/arch/s390/Kconfig
> > > > @@ -135,6 +135,7 @@ config S390
> > > >  	select GENERIC_SMP_IDLE_THREAD
> > > >  	select GENERIC_TIME_VSYSCALL
> > > >  	select GENERIC_VDSO_TIME_NS
> > > > +	select GENERIC_IOREMAP
> > > 
> > > I think you should add the "if PCI" from the diff in your last mail to
> > > this patch.
> > 
> > That's reasonable, will do.
> > 
> > The code change in driver should be posted separately to get reviewing
> > from the relevant drvier maintainers. I may wrap it into this series in
> > next post so that people know its background.
> 
> I agree about doing the driver change separately. Since the problem
> already exists one could send it separately. If you want I can take of
> that too.

Both is fine to me, since you suggested the fix.

> 
> > 
> > > >  	select HAVE_ALIGNED_STRUCT_PAGE if SLUB
> > > >  	select HAVE_ARCH_AUDITSYSCALL
> > > >  	select HAVE_ARCH_JUMP_LABEL
> > ......
> > > > diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
> > > > index 73cdc5539384..3c00dc7d79bc 100644
> > > > --- a/arch/s390/pci/pci.c
> > > > +++ b/arch/s390/pci/pci.c
> > > > @@ -244,64 +244,25 @@ void __iowrite64_copy(void __iomem *to, const void *from, size_t count)
> > > >         zpci_memcpy_toio(to, from, count);
> > > >  }
> > > >  
> > > > -static void __iomem *__ioremap(phys_addr_t addr, size_t size, pgprot_t prot)
> > > > +void __iomem *
> > > > +arch_ioremap(phys_addr_t *paddr, size_t size, unsigned long *prot_val)
> > > >  {
> > > > -	unsigned long offset, vaddr;
> > > > -	struct vm_struct *area;
> > > > -	phys_addr_t last_addr;
> > > > -
> > > > -	last_addr = addr + size - 1;
> > > > -	if (!size || last_addr < addr)
> > > > -		return NULL;
> > > > -
> > > > +	/*
> > > > +	 * When PCI MIO instructions are unavailable the "physical" address
> > > > +	 * encodes a hint for accessing the PCI memory space it represents.
> > > > +	 * Just pass it unchanged such that ioread/iowrite can decode it.
> > > > +	 */
> > > >  	if (!static_branch_unlikely(&have_mio))
> > > > -		return (void __iomem *) addr;
> > > > -
> > > > -	offset = addr & ~PAGE_MASK;
> > > > -	addr &= PAGE_MASK;
> > > > -	size = PAGE_ALIGN(size + offset);
> > > > -	area = get_vm_area(size, VM_IOREMAP);
> > > > -	if (!area)
> > > > -		return NULL;
> > > > -
> > > > -	vaddr = (unsigned long) area->addr;
> > > > -	if (ioremap_page_range(vaddr, vaddr + size, addr, prot)) {
> > > > -		free_vm_area(area);
> > > > -		return NULL;
> > > > -	}
> > > > -	return (void __iomem *) ((unsigned long) area->addr + offset);
> > > > +		return (void __iomem *) *paddr;
> > > 
> > > nit: no space after the cast
> > 
> > Sorry, remember you pointed this out in v2, while I didn't get what
> > it is. Could you be more specific or give the right line of code?
> > 
> > Are you suggesting below line? 
> > 
> > -	return (void __iomem *) ((unsigned long) area->addr + offset);
> > +		return (void __iomem *)*paddr;
> 
> Yes, though I did just check and somehow checkpatch doesn't complain,
> maybe because of the dereference. I do think I remember it complaining
> but I guess if it doesn't you might as well keep it this way.

OK, I will keep it unless checkpatch complaim about it. Thanks.