linux-kernel - Re: [PATCH] riscv: make ZONE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ZvJemFN1qdvi8qo-@infradead.org>
Date: Mon, 23 Sep 2024 23:39:20 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Vladimir Kondratiev <Vladimir.Kondratiev@...ileye.com>
Cc: Christoph Hellwig <hch@...radead.org>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH] riscv: make ZONE_DMA32 optional

On Sun, Sep 22, 2024 at 10:06:59AM +0000, Vladimir Kondratiev wrote:
> This is the whole point - there are platforms where you can't allocate 32-bit
> dma-able memory.

Ugg.  They will be broke for all kinds of devices (plug in PCIe devices
IP IP blocks).

> Unless there's IOMMU or some platform specific tricks,
> DMA address is same as physical address.

Well, that's where the usual platform specific trick is, as the
platforms with high DRAM either have a mapping between physical
and DMA range (see the dma_ranges concept in the DMA and OF code)
or a mirror of the higher addresses.  Or very rarely (e.g. sparc)
a required IOMMU that is always used.