linux-kernel - Re: [PATCH v4 09/16] s390: mm: Convert to GENERIC

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Message-ID: <Y/SvqcWQ+5sgozX/@MiWiFi-R3L-srv>
Date:   Tue, 21 Feb 2023 19:48:57 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Niklas Schnelle <schnelle@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, christophe.leroy@...roup.eu,
        hch@...radead.org, agordeev@...ux.ibm.com,
        wangkefeng.wang@...wei.com, David.Laight@...lab.com,
        shorne@...il.com, arnd@...db.de,
        Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>, linux-s390@...r.kernel.org
Subject: Re: [PATCH v4 09/16] s390: mm: Convert to GENERIC_IOREMAP

On 02/16/23 at 05:21pm, Niklas Schnelle wrote:
> On Thu, 2023-02-16 at 20:34 +0800, Baoquan He wrote:
> > By taking GENERIC_IOREMAP method, the generic generic_ioremap_prot(),
> > generic_iounmap(), and their generic wrapper ioremap_prot(), ioremap()
> > and iounmap() are all visible and available to arch. Arch needs to
> > provide wrapper functions to override the generic versions if there's
> > arch specific handling in its ioremap_prot(), ioremap() or iounmap().
> > This change will simplify implementation by removing duplicated codes
> > with generic_ioremap_prot() and generic_iounmap(), and has the equivalent
> > functioality as before.
> > 
> > Here, add wrapper functions ioremap_prot() and iounmap() for s390's
> > special operation when ioremap() and iounmap().
> > 
> > Signed-off-by: Baoquan He <bhe@...hat.com>
> > Cc: Niklas Schnelle <schnelle@...ux.ibm.com>
> > Cc: Gerald Schaefer <gerald.schaefer@...ux.ibm.com>
> > Cc: Heiko Carstens <hca@...ux.ibm.com>
> > Cc: Vasily Gorbik <gor@...ux.ibm.com>
> > Cc: Alexander Gordeev <agordeev@...ux.ibm.com>
> > Cc: Christian Borntraeger <borntraeger@...ux.ibm.com>
> > Cc: Sven Schnelle <svens@...ux.ibm.com>
> > Cc: linux-s390@...r.kernel.org
> > ---
> >  arch/s390/Kconfig          |  1 +
> >  arch/s390/include/asm/io.h | 21 ++++++++------
> >  arch/s390/pci/pci.c        | 57 +++++++-------------------------------
> >  3 files changed, 23 insertions(+), 56 deletions(-)
> 
> Thanks for the patch. This is a very clear improvement for us! I tested
> this series with s390 systems with and without the PCI memory-I/O (MIO)
> support and everything works as expected.
> 
> One thing I did stumble upon but which is independent from this patch
> is that I think memremap(…, MEMREMAP_WB) on system RAM outside the
> direct map is broken for us. At least on systems without PCI memory-I/O
> support. I think with this series it would be much easier to fix
> though. Basically I think we would have to define arch_memremap_wb() to
> generic_ioremap_prot(…, PAGE_KERNEL) and then have iounmap() check
> is_ioremap_addr() to see if it is an actual mapping or an address
> cookie. But again this is independent of this patch which doesn't
> change the behavior in this area.

OK, I can check this after this patchset done.

> 
> So feel free to add my:
> 
> Reviewed-by: Niklas Schnelle <schnelle@...ux.ibm.com>
> Tested-by: Niklas Schnelle <schnelle@...ux.ibm.com>

Thanks a lot, will add these when repost.