linux-kernel - Re: [PATCH 3/5] x86/mm: Introduce and export interface arch_clean_nonsnoop

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Message-ID: <ZktZDmcNnsHhp4Tm@infradead.org>
Date: Mon, 20 May 2024 07:07:10 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Yan Zhao <yan.y.zhao@...el.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org,
	alex.williamson@...hat.com, jgg@...dia.com, kevin.tian@...el.com,
	iommu@...ts.linux.dev, pbonzini@...hat.com, seanjc@...gle.com,
	dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
	tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
	corbet@....net, joro@...tes.org, will@...nel.org,
	robin.murphy@....com, baolu.lu@...ux.intel.com, yi.l.liu@...el.com,
	Russell King <linux@...linux.org.uk>
Subject: Re: [PATCH 3/5] x86/mm: Introduce and export interface
 arch_clean_nonsnoop_dma()

On Tue, May 07, 2024 at 02:20:44PM +0800, Yan Zhao wrote:
> Introduce and export interface arch_clean_nonsnoop_dma() to flush CPU
> caches for memory involved in non-coherent DMAs (DMAs that lack CPU cache
> snooping).

Err, no.  There should really be no exported cache manipulation macros,
as drivers are almost guaranteed to get this wrong.  I've added
Russell to the Cc list who has been extremtly vocal about this at least
for arm.