Linux PCI subsystem development
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From: Arnd Bergmann <arnd@linaro.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Nikita Yushchenko <nikita.yoush@cogentembedded.com>,
	Keith Busch <keith.busch@intel.com>,
	Sagi Grimberg <sagi@grimberg.me>, Jens Axboe <axboe@fb.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-renesas-soc@vger.kernel.org,
	Simon Horman <horms@verge.net.au>,
	linux-pci@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>,
	artemi.ivanov@cogentembedded.com,
	linux-arm-kernel@lists.infradead.org
Subject: Re: NVMe vs DMA addressing limitations
Date: Tue, 10 Jan 2017 11:54:26 +0100	[thread overview]
Message-ID: <1967203.EWsxCL11oI@wuerfel> (raw)
In-Reply-To: <20170110070719.GA17208@lst.de>

On Tuesday, January 10, 2017 8:07:20 AM CET Christoph Hellwig wrote:
> On Tue, Jan 10, 2017 at 09:47:21AM +0300, Nikita Yushchenko wrote:
> > I'm now working with HW that:
> > - is now way "low end" or "obsolete", it has 4G of RAM and 8 CPU cores,
> > and is being manufactured and developed,
> > - has 75% of it's RAM located beyond first 4G of address space,
> > - can't physically handle incoming PCIe transactions addressed to memory
> > beyond 4G.
> 
> It might not be low end or obselete, but it's absolutely braindead.
> Your I/O performance will suffer badly for the life of the platform
> because someone tries to save 2 cents, and there is not much we can do
> about it.

Unfortunately it is a common problem for arm64 chips that were designed
by taking a 32-bit SoC and replacing the CPU core. The swiotlb is the
right workaround for this, and I think we all agree that we should
just make it work correctly.

	Arnd

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  parent reply	other threads:[~2017-01-10 10:54 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-29 20:45 [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit DMA mask Nikita Yushchenko
2016-12-29 20:45 ` [PATCH 2/2] rcar-pcie: set host bridge's " Nikita Yushchenko
2016-12-29 21:18 ` [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit " Arnd Bergmann
2016-12-30  9:46 ` Sergei Shtylyov
2016-12-30 10:06   ` Sergei Shtylyov
2017-01-03 18:44 ` Will Deacon
2017-01-03 19:00   ` Nikita Yushchenko
2017-01-03 19:01   ` Nikita Yushchenko
2017-01-03 20:13     ` Grygorii Strashko
2017-01-03 20:23       ` Nikita Yushchenko
2017-01-03 23:13   ` Arnd Bergmann
2017-01-04  6:24     ` Nikita Yushchenko
2017-01-04 13:29       ` Arnd Bergmann
2017-01-04 14:30         ` Nikita Yushchenko
2017-01-04 14:46           ` Arnd Bergmann
2017-01-04 15:29             ` Nikita Yushchenko
2017-01-06 11:10               ` Arnd Bergmann
2017-01-06 13:47                 ` Nikita Yushchenko
2017-01-09 14:05                   ` Arnd Bergmann
2017-01-09 20:34                     ` Nikita Yushchenko
2017-01-09 20:57                       ` Christoph Hellwig
2017-01-10  6:47                         ` NVMe vs DMA addressing limitations Nikita Yushchenko
2017-01-10  7:07                           ` Christoph Hellwig
2017-01-10  7:31                             ` Nikita Yushchenko
2017-01-10 11:01                               ` Arnd Bergmann
2017-01-10 14:48                                 ` Christoph Hellwig
2017-01-10 15:02                                   ` Arnd Bergmann
2017-01-12 10:09                                   ` Sagi Grimberg
2017-01-12 11:56                                     ` Arnd Bergmann
2017-01-12 13:07                                       ` Christoph Hellwig
2017-01-10 10:54                             ` Arnd Bergmann [this message]
2017-01-10 10:47                         ` [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit DMA mask Arnd Bergmann
2017-01-10 14:44                           ` Christoph Hellwig
2017-01-10 15:00                             ` Arnd Bergmann

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