From: Catalin Marinas <catalin.marinas@arm.com>
To: Will Deacon <will@kernel.org>
Cc: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@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: Wed, 7 Oct 2026 11:04:05 +0100 [thread overview]
Message-ID: <asYZFXGyafRjjBS0@arm.com> (raw)
In-Reply-To: <asVs3doaJ4WrT3M2@willie-the-truck>
On Tue, Oct 06, 2026 at 10:49:17PM +0100, Will Deacon wrote:
> On Thu, Sep 24, 2026 at 11:37:54AM +0530, Aneesh Kumar K.V (Arm) wrote:
> > @@ -496,7 +516,8 @@ swiotlb_select_pool_policy(unsigned int flags)
> > if (swiotlb_force_disable)
> > return SWIOTLB_POOL_NONE;
> >
> > - if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
> > + if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT) &&
> > + !restricted_dma_pool_present)
> > return SWIOTLB_POOL_CC_GUEST;
>
> I think this check on the restricted DMA pool is too general -- the pool
> could be tied to a specific DMA-capable peripheral and so treating its
> presence as a global property isn't right.
I agree it's a hack but that was the simplest way to avoid the pVMs
getting a bounce buffer after this patch. More than happy to leave it
out and reduce the buffer on cmdline or we come up with some better
heuristics.
Another option could be the arch code passing another flag that it
doesn't want an encrypted pool (e.g. when running in a pKVM guest) but I
don't particularly this either. The arch code doesn't know whether
there's an alternative pool.
That said, such heuristics should have been a separate patch to make it
easier to review/drop.
--
Catalin
next prev parent reply other threads:[~2026-10-07 10:04 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20260924060823eucas1p1d27fbf57221c9b4c0e9831a9b0cdd7d3@eucas1p1.samsung.com>
2026-09-24 6:07 ` [PATCH v6 0/8] dma: swiotlb: Centralize default pool policy and sizing Aneesh Kumar K.V (Arm)
2026-09-24 6:07 ` [PATCH v6 1/8] dma: swiotlb: Rename swiotlb_size_or_default() Aneesh Kumar K.V (Arm)
2026-09-24 6:07 ` [PATCH v6 2/8] dma: swiotlb: Consolidate slab rounding Aneesh Kumar K.V (Arm)
2026-09-24 6:07 ` [PATCH v6 3/8] dma: swiotlb: Track whether the pool size was explicitly set Aneesh Kumar K.V (Arm)
2026-09-24 6:07 ` [PATCH v6 4/8] dma: swiotlb: Centralize default pool policy selection Aneesh Kumar K.V (Arm)
2026-09-24 6:07 ` [PATCH v6 5/8] dma: swiotlb: Centralize minimal pool sizing Aneesh Kumar K.V (Arm)
2026-09-24 6:07 ` [PATCH v6 6/8] dma: swiotlb: Centralize memory-encryption " Aneesh Kumar K.V (Arm)
2026-10-06 21:49 ` Will Deacon
2026-10-07 10:04 ` Catalin Marinas [this message]
2026-10-07 10:43 ` Will Deacon
2026-10-07 11:13 ` Catalin Marinas
2026-10-07 12:15 ` Aneesh Kumar K.V
2026-10-07 12:17 ` Aneesh Kumar K.V
2026-09-24 6:07 ` [PATCH v6 7/8] dma: swiotlb: Add an overridable architecture pool opt-out Aneesh Kumar K.V (Arm)
2026-09-24 6:07 ` [PATCH v6 8/8] dma: swiotlb: Remove SWIOTLB_ANY Aneesh Kumar K.V (Arm)
2026-09-25 8:57 ` [PATCH v6 0/8] dma: swiotlb: Centralize default pool policy and sizing Marek Szyprowski
2026-10-06 21:42 ` Marek Szyprowski
2026-10-06 21:52 ` Will Deacon
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=asYZFXGyafRjjBS0@arm.com \
--to=catalin.marinas@arm.com \
--cc=Suzuki.Poulose@arm.com \
--cc=agordeev@linux.ibm.com \
--cc=aik@amd.com \
--cc=alex@ghiti.fr \
--cc=aneesh.kumar@kernel.org \
--cc=aou@eecs.berkeley.edu \
--cc=borntraeger@linux.ibm.com \
--cc=bp@alien8.de \
--cc=chenhuacai@kernel.org \
--cc=chleroy@kernel.org \
--cc=corbet@lwn.net \
--cc=dan.j.williams@intel.com \
--cc=dave.hansen@linux.intel.com \
--cc=gerald.schaefer@linux.ibm.com \
--cc=gor@linux.ibm.com \
--cc=hca@linux.ibm.com \
--cc=hpa@zytor.com \
--cc=iommu@lists.linux.dev \
--cc=jgg@ziepe.ca \
--cc=jiaxun.yang@flygoat.com \
--cc=jiri@resnulli.us \
--cc=kernel@xen0n.name \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mips@vger.kernel.org \
--cc=linux-riscv@lists.infradead.org \
--cc=linux-s390@vger.kernel.org \
--cc=linux@armlinux.org.uk \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=loongarch@lists.linux.dev \
--cc=luto@kernel.org \
--cc=m.szyprowski@samsung.com \
--cc=maddy@linux.ibm.com \
--cc=mark.rutland@arm.com \
--cc=maz@kernel.org \
--cc=mingo@redhat.com \
--cc=mpe@ellerman.id.au \
--cc=npiggin@gmail.com \
--cc=palmer@dabbelt.com \
--cc=peterz@infradead.org \
--cc=pjw@kernel.org \
--cc=ptesarik@suse.com \
--cc=rdunlap@infradead.org \
--cc=ritesh.list@gmail.com \
--cc=robin.murphy@arm.com \
--cc=skhan@linuxfoundation.org \
--cc=smostafa@google.com \
--cc=sshegde@linux.ibm.com \
--cc=sstabellini@kernel.org \
--cc=steven.price@arm.com \
--cc=svens@linux.ibm.com \
--cc=tglx@kernel.org \
--cc=tsbogend@alpha.franken.de \
--cc=will@kernel.org \
--cc=x86@kernel.org \
--cc=yilun.xu@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®