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Date:   Wed, 12 Oct 2022 13:52:04 +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
Message-ID: <Y0ZWBMKKIuf5Q+qk@MiWiFi-R3L-srv>
References: <20221009103114.149036-1-bhe@redhat.com>
 <20221009103114.149036-10-bhe@redhat.com>
 <b6ac5c44917390b9a5cc7ebb87a089568279c459.camel@linux.ibm.com>
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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.

> 
> >  	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;

> 
> > +	return NULL;
> >  }
> >  
> > -void __iomem *ioremap_prot(phys_addr_t addr, size_t size, unsigned long prot)
> > +bool arch_iounmap(void __iomem *addr)
> >  {
> > -	return __ioremap(addr, size, __pgprot(prot));
> > -}
> > -EXPORT_SYMBOL(ioremap_prot);
> > -
> > -void __iomem *ioremap(phys_addr_t addr, size_t size)
> > -{
> > -	return __ioremap(addr, size, PAGE_KERNEL);
> > -}
> > -EXPORT_SYMBOL(ioremap);
> > -
> > -void __iomem *ioremap_wc(phys_addr_t addr, size_t size)
> > -{
> > -	return __ioremap(addr, size, pgprot_writecombine(PAGE_KERNEL));
> > -}
> > -EXPORT_SYMBOL(ioremap_wc);
> > -
> > -void __iomem *ioremap_wt(phys_addr_t addr, size_t size)
> > -{
> > -	return __ioremap(addr, size, pgprot_writethrough(PAGE_KERNEL));
> > -}
> > -EXPORT_SYMBOL(ioremap_wt);
> > -
> > -void iounmap(volatile void __iomem *addr)
> > -{
> > -	if (static_branch_likely(&have_mio))
> > -		vunmap((__force void *) ((unsigned long) addr & PAGE_MASK));
> > +	if (!static_branch_likely(&have_mio))
> > +		return false;
> > +	return true;
> >  }
> > -EXPORT_SYMBOL(iounmap);
> >  
> >  /* Create a virtual mapping cookie for a PCI BAR */
> >  static void __iomem *pci_iomap_range_fh(struct pci_dev *pdev, int bar,
> 
> Gave this a round of testing on s390 with both the MIO and non-MIO
> cases. I also see you addressed my previous comments and it looks good
> to me. As you showed in the other mail the compile error is a pre
> existing problem so shouldn't influence this change. So assuming you
> add the "if PCI" and the nit above you can add my:

Thanks a lot, will add that part to this patch and add your tags.

> 
> Tested-by: Niklas
> Schnelle <schnelle@linux.ibm.com>
> Reviewed-by: Niklas Schnelle
> <schnelle@linux.ibm.com>
> 
>