From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Stefan Wahren <stefan.wahren@i2se.com>,
Florian Fainelli <f.fainelli@gmail.com>,
Robin Murphy <robin.murphy@arm.com>,
Christoph Hellwig <hch@lst.de>,
Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] ARM: mm: Fix ARCH_LOW_ADDRESS_LIMIT when CONFIG_ZONE_DMA
Date: Sat, 3 Jun 2023 13:38:34 +0100 [thread overview]
Message-ID: <ZHs0SgtfX5Gvvu/D@shell.armlinux.org.uk> (raw)
In-Reply-To: <121092e9-a718-45f7-938d-a2cff7e92214@app.fastmail.com>
On Sat, Jun 03, 2023 at 02:33:49PM +0200, Arnd Bergmann wrote:
> Changing the low address limit by itself makes the swiotlb work
> correctly, but for performance we also want to avoid having to
> use the swiotlb at all when dealing with the zero page.
How often is the zero page used for DMA _to_ a device (it should never
be used for DMA _from_ a device.) ? It doesn't sound that useful to me,
since it can only be used for writing zeros.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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next prev parent reply other threads:[~2023-06-03 12:39 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-03 9:06 [PATCH] ARM: mm: Fix ARCH_LOW_ADDRESS_LIMIT when CONFIG_ZONE_DMA Stefan Wahren
2023-06-03 12:33 ` Arnd Bergmann
2023-06-03 12:38 ` Russell King (Oracle) [this message]
2023-06-03 12:59 ` Arnd Bergmann
2023-06-03 13:52 ` Russell King (Oracle)
[not found] ` <20230603135820.GA13150@wunner.de>
2023-09-06 10:31 ` Stefan Wahren
2023-09-06 11:38 ` Robin Murphy
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