linux-kernel - Re: [PATCH v2 3/3] asm-generic/io.h: Fix !CONFIG_GENERIC_IOMAP pci

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Date:   Thu, 17 Sep 2020 10:29:39 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     linux-kernel@...r.kernel.org,
        George Cherian <george.cherian@...vell.com>,
        Arnd Bergmann <arnd@...db.de>, Will Deacon <will@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Yang Yingliang <yangyingliang@...wei.com>,
        linux-pci@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH v2 3/3] asm-generic/io.h: Fix !CONFIG_GENERIC_IOMAP
 pci_iounmap() implementation

On Wed, Sep 16, 2020 at 03:51:11PM +0100, Catalin Marinas wrote:
> On Wed, Sep 16, 2020 at 12:06:58PM +0100, Lorenzo Pieralisi wrote:
> > For arches that do not select CONFIG_GENERIC_IOMAP, the current
> > pci_iounmap() function does nothing causing obvious memory leaks
> > for mapped regions that are backed by MMIO physical space.
> > 
> > In order to detect if a mapped pointer is IO vs MMIO, a check must made
> > available to the pci_iounmap() function so that it can actually detect
> > whether the pointer has to be unmapped.
> > 
> > In configurations where CONFIG_HAS_IOPORT_MAP && !CONFIG_GENERIC_IOMAP,
> > a mapped port is detected using an ioport_map() stub defined in
> > asm-generic/io.h.
> > 
> > Use the same logic to implement a stub (ie __pci_ioport_unmap()) that
> > detects if the passed in pointer in pci_iounmap() is IO vs MMIO to
> > iounmap conditionally and call it in pci_iounmap() fixing the issue.
> > 
> > Leave __pci_ioport_unmap() as a NOP for all other config options.
> > 
> > Reported-by: George Cherian <george.cherian@...vell.com>
> > Link: https://lore.kernel.org/lkml/20200905024811.74701-1-yangyingliang@huawei.com
> > Link: https://lore.kernel.org/lkml/20200824132046.3114383-1-george.cherian@marvell.com
> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> > Cc: Arnd Bergmann <arnd@...db.de>
> > Cc: George Cherian <george.cherian@...vell.com>
> > Cc: Will Deacon <will@...nel.org>
> > Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> > Cc: Catalin Marinas <catalin.marinas@....com>
> > Cc: Yang Yingliang <yangyingliang@...wei.com>
> > ---
> >  include/asm-generic/io.h | 39 +++++++++++++++++++++++++++------------
> >  1 file changed, 27 insertions(+), 12 deletions(-)
> 
> This works for me. The only question I have is whether pci_iomap.h is
> better than io.h for __pci_ioport_unmap(). These headers are really
> confusing.

Yes they are, in total honesty there is much more to do to make them
sane, this patch is just a band-aid.

I thought about moving this stuff into pci_iomap.h, though that
file is included _independently_ from io.h from some arches so
I tried to keep everything in io.h to minimize disruption.

We can merge this patch - since it is a fix after all - and then I can
try to improve the whole pci_iounmap() includes.

> Either way:
> 
> Reviewed-by: Catalin Marinas <catalin.marinas@....com>

Thanks a lot. I'd appreciate a tested-by from the George as he is
the one who reported the problem.

Lorenzo