linux-kernel - Re: [v5 PATCH] arm64: mm: force write fault for atomic RMW instructions

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Message-ID: <1845bd3d-499d-479a-8c10-14aab8966e37@arm.com>
Date: Tue, 2 Jul 2024 15:51:19 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: David Hildenbrand <david@...hat.com>,
 Catalin Marinas <catalin.marinas@....com>,
 Yang Shi <yang@...amperecomputing.com>
Cc: "Christoph Lameter (Ampere)" <cl@...two.org>, will@...nel.org,
 anshuman.khandual@....com, scott@...amperecomputing.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Jinjiang Tu <tujinjiang@...wei.com>
Subject: Re: [v5 PATCH] arm64: mm: force write fault for atomic RMW
 instructions

>> I don't think that really applies in your migration
>> case, because you are definitely going to write all the memory eventually, I
>> think?
> 
> Especially with memory ballooning and things like free-page-reporting we might
> be migrating a whole bunch of zero-memory and only have to make sure that the
> destination is actually zero. We don't want to consume memory.

Ahh you know if the contents of a page being migrated is all zero. In that case,
I get it. Thanks!