Re: [PATCH v6 6/8] dma: swiotlb: Centralize memory-encryption pool sizing

From: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
To: Kohei Enju <enju.kohei@fujitsu.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	iommu@lists.linux.dev, linux-kernel@vger.kernel.org,
	Robin Murphy <robin.murphy@arm.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Shuah Khan <skhan@linuxfoundation.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Marc Zyngier <maz@kernel.org>,
	Steven Price <steven.price@arm.com>,
	Suzuki K Poulose <Suzuki.Poulose@arm.com>,
	Jiri Pirko <jiri@resnulli.us>, Jason Gunthorpe <jgg@ziepe.ca>,
	Mostafa Saleh <smostafa@google.com>,
	Petr Tesarik <ptesarik@suse.com>,
	Alexey Kardashevskiy <aik@amd.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Xu Yilun <yilun.xu@linux.intel.com>,
	Madhavan Srinivasan <maddy@linux.ibm.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Nicholas Piggin <npiggin@gmail.com>,
	"Christophe Leroy (CS GROUP)" <chleroy@kernel.org>,
	"Ritesh Harjani (IBM)" <ritesh.list@gmail.com>,
	Shrikanth Hegde <sshegde@linux.ibm.com>,
	Alexander Gordeev <agordeev@linux.ibm.com>,
	Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Christian Borntraeger <borntraeger@linux.ibm.com>,
	Sven Schnelle <svens@linux.ibm.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Russell King <linux@armlinux.org.uk>,
	Huacai Chen <chenhuacai@kernel.org>,
	WANG Xuerui <kernel@xen0n.name>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Jiaxun Yang <jiaxun.yang@flygoat.com>,
	Paul Walmsley <pjw@kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alex@ghiti.fr>,
	Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev,
	linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org,
	x86@kernel.org
Subject: Re: [PATCH v6 6/8] dma: swiotlb: Centralize memory-encryption pool sizing
Date: Thu, 12 Nov 2026 15:43:59 +0530	[thread overview]
Message-ID: <yq5a33t6qrvc.fsf@kernel.org> (raw)
In-Reply-To: <avRKiCBs81XSYMqW@FCCLS0092175.localdomain>

Kohei Enju <enju.kohei@fujitsu.com> writes:

> Hi Aneesh,
>
> On 11/01 09:47, Aneesh Kumar K.V wrote:
> [...]
>> >
>> > Hi Aneesh,
>> >

 [ ... 35 lines skipped ... ] 

> Overall, I would prefer the dynamic sizing approach. However, I believe
> the initial pool size still matters.
>
> Also, as Catalin pointed out earlier in the following message:
>
>     https://lore.kernel.org/all/ann6noRzoPLL9kDY@arm.com/
>
> the arm64 adjustment also reduces the target size used for dynamic
> pool allocation, since both the initial pool and dynamic allocation
> currently use default_nslabs.
>
> I am testing the patch below to decouple the initial pool size from the
> dynamic allocation target. It adds swiotlb_adjust_initial_size() for
> callers that only want to reduce the initial allocation, while keeping
> the existing swiotlb_adjust_size() semantics for callers that want to
> adjust both sizes.
>

Should we instead update the logic so that reducing the swiotlb size
leaves the dynamic allocation size unchanged, while increasing it also
bumps the dynamic allocation size?

-aneesh