Re: [PATCH] asm-generic: io: Fix ioport_map() for !CONFIG_GENERIC_IOMAP && CONFIG_INDIRECT_PIO

From: Will Deacon <will.deacon@arm.com>
To: Andrew Murray <andrew.murray@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	yuanzhichang@hisilicon.com, dann.frazier@canonical.com,
	gabriele.paoloni@huawei.com, bhelgaas@google.com,
	andy.shevchenko@gmail.com, linux-pci@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, suzuki.poulose@arm.com,
	jean-philippe.brucker@arm.com
Subject: Re: [PATCH] asm-generic: io: Fix ioport_map() for !CONFIG_GENERIC_IOMAP && CONFIG_INDIRECT_PIO
Date: Thu, 13 Sep 2018 14:02:14 +0100	[thread overview]
Message-ID: <20180913130214.GA13242@arm.com> (raw)
In-Reply-To: <1536842907-51732-1-git-send-email-andrew.murray@arm.com>

On Thu, Sep 13, 2018 at 01:48:27PM +0100, Andrew Murray wrote:
> The !CONFIG_GENERIC_IOMAP version of ioport_map uses MMIO_UPPER_LIMIT to
> prevent users from making I/O accesses outside the expected I/O range -
> however it erroneously treats MMIO_UPPER_LIMIT as a mask which is
> contradictory to its other users.
> 
> The introduction of CONFIG_INDIRECT_PIO, which subtracts an arbitrary
> amount from IO_SPACE_LIMIT to form MMIO_UPPER_LIMIT, results in ioport_map
> mangling the given port rather than capping it.
> 
> We address this by aligning more closely with the CONFIG_GENERIC_IOMAP
> implementation of ioport_map by using the comparison operator and
> returning NULL where the port exceeds MMIO_UPPER_LIMIT. Though note that
> we preserve the existing behavior of masking with IO_SPACE_LIMIT such that
> we don't break existing buggy drivers that somehow rely on this masking.
> 
> Fixes: 5745392e0c2b ("PCI: Apply the new generic I/O management on PCI IO hosts")
> Reported-by: Will Deacon <will.deacon@arm.com>
> Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> ---
>  include/asm-generic/io.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
> index 66d1d45..d356f80 100644
> --- a/include/asm-generic/io.h
> +++ b/include/asm-generic/io.h
> @@ -1026,7 +1026,8 @@ static inline void __iomem *ioremap_wt(phys_addr_t offset, size_t size)
>  #define ioport_map ioport_map
>  static inline void __iomem *ioport_map(unsigned long port, unsigned int nr)
>  {
> -	return PCI_IOBASE + (port & MMIO_UPPER_LIMIT);
> +	port &= IO_SPACE_LIMIT;
> +	return (port > MMIO_UPPER_LIMIT) ? NULL : PCI_IOBASE + port;
>  }
>  #endif

Thanks, that fixes legacy virtio PCI devices under kvmtool, so:

Tested-by: Will Deacon <will.deacon@arm.com>

Will