linux-kernel - Re: [PATCH v17 19/35] arch/mm: Export direct {un,}map functions

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Date: Thu, 22 Feb 2024 23:09:40 -0800
From: Christoph Hellwig <hch@...radead.org>
To: Elliot Berman <quic_eberman@...cinc.com>
Cc: Alex Elder <elder@...aro.org>,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Murali Nalajal <quic_mnalajal@...cinc.com>,
	Trilok Soni <quic_tsoni@...cinc.com>,
	Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
	Carl van Schaik <quic_cvanscha@...cinc.com>,
	Philip Derrin <quic_pderrin@...cinc.com>,
	Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>,
	Jonathan Corbet <corbet@....net>, Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Fuad Tabba <tabba@...gle.com>,
	Sean Christopherson <seanjc@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-arm-msm@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org
Subject: Re: [PATCH v17 19/35] arch/mm: Export direct {un,}map functions

On Thu, Feb 22, 2024 at 03:16:42PM -0800, Elliot Berman wrote:
> Firmware and hypervisor drivers can donate system heap memory to their
> respective firmware/hypervisor entities. Those drivers should unmap the
> pages from the kernel's logical map before doing so.
> 
> Export can_set_direct_map, set_direct_map_invalid_noflush, and
> set_direct_map_default_noflush.

Err, not they should not.  And not using such super low-level interfaces
from modular code.