From: Christoph Hellwig <hch@infradead•org>
To: Julien Grall <Julien.Grall@arm•com>
Cc: Peng Fan <peng.fan@nxp•com>,
"sstabellini@kernel•org" <sstabellini@kernel•org>,
Catalin Marinas <Catalin.Marinas@arm•com>,
"linux@armlinux•org.uk" <linux@armlinux•org.uk>,
dl-linux-imx <linux-imx@nxp•com>,
"xen-devel@lists•xenproject.org" <xen-devel@lists•xenproject.org>,
nd <nd@arm•com>, "will@kernel•org" <will@kernel•org>,
"linux-arm-kernel@lists•infradead.org"
<linux-arm-kernel@lists•infradead.org>,
Robin Murphy <Robin.Murphy@arm•com>
Subject: Re: [PATCH V2] arm: xen: mm: use __GPF_DMA32 for arm64
Date: Fri, 30 Aug 2019 01:58:07 -0700 [thread overview]
Message-ID: <20190830085807.GA15771@infradead.org> (raw)
In-Reply-To: <d7477406-a8a0-5c3c-13dc-2c84e27b8afa@arm.com>
Can we take a step back and figure out what we want to do here?
AFAICS this function allocates memory for the swiotlb-xen buffer,
and that means it must be <= 32-bit addressable to satisfy the DMA API
guarantees. That means we generally want to use GFP_DMA32 everywhere
that exists, but on systems with odd zones we might want to dip into
GFP_DMA. This also means swiotlb-xen doesn't actually do the right
thing on x86 at the moment. So shouldn't we just have one common
routine in swiotlb-xen.c that checks if we have CONFIG_ZONE_DMA32
set, then try GFP_DMA32, and if not check if CONFIG_ZONE_DMA is set
and then try that, else default to GFP_KERNEL?
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next prev parent reply other threads:[~2019-08-30 8:58 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-30 2:28 [PATCH V2] arm: xen: mm: use __GPF_DMA32 for arm64 Peng Fan
2019-08-30 8:39 ` Julien Grall
2019-08-30 8:58 ` Christoph Hellwig [this message]
2019-08-31 2:40 ` Stefano Stabellini
2019-09-02 15:57 ` Christoph Hellwig
2019-09-03 11:48 ` Juergen Gross
2019-09-11 2:06 ` Peng Fan
2019-09-11 19:12 ` Stefano Stabellini
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