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Date:   Wed, 9 Sep 2020 14:54:01 +0100
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc:     George Cherian <gcherian@marvell.com>,
        Yang Yingliang <yangyingliang@huawei.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "will.deacon@arm.com" <will.deacon@arm.com>,
        "bhelgaas@google.com" <bhelgaas@google.com>,
        "guohanjun@huawei.com" <guohanjun@huawei.com>
Subject: Re: [PATCH] arm64: PCI: fix memleak when calling pci_iomap/unmap()
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On Wed, Sep 09, 2020 at 12:36:13PM +0100, Lorenzo Pieralisi wrote:
> On Mon, Sep 07, 2020 at 12:21:19PM +0100, Catalin Marinas wrote:
> > On Mon, Sep 07, 2020 at 10:51:21AM +0000, George Cherian wrote:
> > > Catalin Marinas <catalin.marinas@arm.com> wrote:
> > > > On Sat, Sep 05, 2020 at 10:48:11AM +0800, Yang Yingliang wrote:
> > > > > diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c index
> > > > > 1006ed2d7c604..ddfa1c53def48 100644
> > > > > --- a/arch/arm64/kernel/pci.c
> > > > > +++ b/arch/arm64/kernel/pci.c
> > > > > @@ -217,4 +217,9 @@ void pcibios_remove_bus(struct pci_bus *bus)
> > > > >  	acpi_pci_remove_bus(bus);
> > > > >  }
> > > > >
> > > > > +void pci_iounmap(struct pci_dev *dev, void __iomem *addr) {
> > > > > +	iounmap(addr);
> > > > > +}
> > > > > +EXPORT_SYMBOL(pci_iounmap);
> > > > 
> > > > So, what's wrong with the generic pci_iounmap() implementation?
> > > > Shouldn't it call iounmap() already?
> > > 
> > > Since ARM64 selects CONFIG_GENERIC_PCI_IOMAP and not
> > > CONFIG_GENERIC_IOMAP,  the pci_iounmap function is reduced to a NULL
> > > function. Due to this, even the managed release variants or even the explicit
> > > pci_iounmap calls doesn't really remove the mappings leading to leak.
> > 
> > Ah, I missed the fact that pci_iounmap() depends on a different
> > config option.
> > 
> > > https://lkml.org/lkml/2020/8/20/28
> > 
> > So is this going to be fixed in the generic code? That would be my
> > preference.
> > 
> > A problem with the iounmap() in the proposed patch is that the region
> > may have been an I/O port, so we could end up unmapping the I/O space.
> 
> It boils down to finding a way to match a VA to a BAR resource so that
> we can mirror on pci_iounmap() what's done in pci_iomap_range() (ie
> check BAR resource flags to define how/if to unmap them), that would do
> as a generic pci_iounmap() implementation.

In the !CONFIG_GENERIC_IOMAP case (arm64), for IORESOURCE_IO,
pci_iomap_range() calls __pci_ioport_map() which, with the default
ioport_map(), it ends up with a simple PCI_IOBASE + (port &
IO_SPACE_LIMIT).

pci_iounmap() could check whether the pointer is in the PCI_IOBASE -
PCI_IOBASE+IO_SPACE_LIMIT range before calling ioremap(), unless the
arch code re-defined ioport_map. Something like below (not even
compiled):

diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
index dabf8cb7203b..fada420c9cd6 100644
--- a/include/asm-generic/io.h
+++ b/include/asm-generic/io.h
@@ -919,6 +919,11 @@ extern void __iomem *pci_iomap(struct pci_dev *dev, int bar, unsigned long max);
 #define pci_iounmap pci_iounmap
 static inline void pci_iounmap(struct pci_dev *dev, void __iomem *p)
 {
+#ifndef ARCH_HAS_IOPORT_MAP
+	if (p >= PCI_IOBASE && p < PCI_IOBASE + IO_SPACE_LIMIT)
+		return;
+	iounmap(p);
+#endif
 }
 #endif
 #endif /* CONFIG_GENERIC_IOMAP */
@@ -1009,7 +1014,9 @@ static inline void __iomem *ioremap_uc(phys_addr_t offset, size_t size)
 
 #ifdef CONFIG_HAS_IOPORT_MAP
 #ifndef CONFIG_GENERIC_IOMAP
-#ifndef ioport_map
+#ifdef ioport_map
+#define ARCH_HAS_IOPORT_MAP
+#else
 #define ioport_map ioport_map
 static inline void __iomem *ioport_map(unsigned long port, unsigned int nr)
 {

-- 
Catalin