linux-kernel - Re: [PATCH v3 12/14] arm64: realm: Support nonsecure ITS emulation shared

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Date: Fri, 7 Jun 2024 17:46:42 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: Steven Price <steven.price@....com>
Cc: Marc Zyngier <maz@...nel.org>, kvm@...r.kernel.org,
	kvmarm@...ts.linux.dev, Will Deacon <will@...nel.org>,
	James Morse <james.morse@....com>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Joey Gouly <joey.gouly@....com>,
	Alexandru Elisei <alexandru.elisei@....com>,
	Christoffer Dall <christoffer.dall@....com>,
	Fuad Tabba <tabba@...gle.com>, linux-coco@...ts.linux.dev,
	Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>
Subject: Re: [PATCH v3 12/14] arm64: realm: Support nonsecure ITS emulation
 shared

On Fri, Jun 07, 2024 at 04:45:14PM +0100, Steven Price wrote:
> On 06/06/2024 19:38, Catalin Marinas wrote:
> > Anyway, we could do some hacking around gen_pool as a temporary solution
> > (maybe as a set of patches on top of this series to be easier to revert)
> > and start investigating a proper decrypted page allocator in parallel.
> > We just need to find a victim that has the page allocator fresh in mind
> > (Ryan or Alexandru ;)).
> 
> Thanks for the suggestions Catalin. I had a go at implementing something
> with gen_pool - the below (very lightly tested) hack seems to work. This
> is on top of the current series.
> 
> I *think* it should also be safe to drop the whole alignment part with
> this custom allocator, which could actually save memory. But I haven't
> quite got my head around that yet.

Thanks Steven. It doesn't look too complex and it solves the memory
wasting. We don't actually free the pages from gen_pool but I don't
think it matters much, the memory would get reused if devices are
removed and re-added.

-- 
Catalin