From: Jason Gunthorpe <jgg@ziepe.ca>
To: Tomasz Jeznach <tjeznach@rivosinc.com>
Cc: Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Anup Patel <apatel@ventanamicro.com>,
Sunil V L <sunilvl@ventanamicro.com>,
Nick Kossifidis <mick@ics.forth.gr>,
Sebastien Boeuf <seb@rivosinc.com>,
Rob Herring <robh+dt@kernel.org>,
Krzysztof Kozlowski <krzk+dt@kernel.org>,
Conor Dooley <conor+dt@kernel.org>,
devicetree@vger.kernel.org, iommu@lists.linux.dev,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
linux@rivosinc.com
Subject: Re: [PATCH v2 5/7] iommu/riscv: Device directory management.
Date: Wed, 24 Apr 2024 20:07:15 -0300 [thread overview]
Message-ID: <20240424230715.GI231144@ziepe.ca> (raw)
In-Reply-To: <CAH2o1u7_YBtS6m1-T56tmxud1mda2gb6tLGVpbBSs15FPcjaGQ@mail.gmail.com>
On Wed, Apr 24, 2024 at 04:01:04PM -0700, Tomasz Jeznach wrote:
> > > + /* Update existing or allocate new entries in device directory */
> > > + for (i = 0; i < fwspec->num_ids; i++) {
> > > + dc = riscv_iommu_get_dc(iommu, fwspec->ids[i], !iommu_domain);
> > > + if (!dc && !iommu_domain)
> > > + continue;
> > > + if (!dc)
> > > + return -ENODEV;
> >
> > But if this fails some of the fwspecs were left in a weird state ?
> >
> > Drivers should try hard to have attach functions that fail and make no
> > change at all or fully succeed.
> >
> > Meaning ideally preallocate any required memory before doing any
> > change to the HW visable structures.
>
> Good point. Done.
> Looking at the fwspec->ids[] I'm assuming nobody will add/modify the
> IDs after iommu_probe_device() completes.
Yes
> > > + /* Swap device context, update TC valid bit as the last operation */
> > > + xchg64(&dc->fsc, fsc);
> > > + xchg64(&dc->ta, ta);
> > > + xchg64(&dc->tc, tc);
> >
> > This doesn't loook right? When you get to adding PAGING suport fsc has
> > the page table pfn and ta has the cache tag, so this will end up
> > tearing the data for sure, eg when asked to replace a PAGING domain
> > with another PAGING domain? That will create a functional/security
> > problem, right?
> >
> > I would encourage you to re-use the ARM sequencing code, ideally moved
> > to some generic helper library. Every iommu driver dealing with
> > multi-quanta descriptors seems to have this same fundamental
> > sequencing problem.
> >
>
> Good point. Reworked.
I suppose by force clearing the v bit before starting the sequence?
That is OK but won't support some non-embedded focused features in the
long run. It is a good approach to get the driver landed though.
> > The release_domain has landed too now. Please don't invent weird NULL
> > domain types that have special meaning. I assume clearing the V bit is
> > a blocking behavior? So please implement a proper blocking domain and
> > set release_domain = &riscv_iommu_blocking and just omit this release
> > function.
> >
>
> Updated to use release_domain, should be cleaner now.
> Clearing TC.V is a blocking (but noisy) behavior, should be fine for
> release domain where devices should be quiesced already.
blocking is fine to be noisy.
Jason
next prev parent reply other threads:[~2024-04-24 23:07 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-18 16:32 [PATCH v2 0/7] Linux RISC-V IOMMU Support Tomasz Jeznach
2024-04-18 16:32 ` [PATCH v2 1/7] dt-bindings: iommu: riscv: Add bindings for RISC-V IOMMU Tomasz Jeznach
2024-04-18 17:04 ` Conor Dooley
2024-04-24 22:37 ` Tomasz Jeznach
2024-04-25 17:11 ` Conor Dooley
2024-04-22 14:04 ` Rob Herring
2024-04-18 16:32 ` [PATCH v2 2/7] iommu/riscv: Add RISC-V IOMMU platform device driver Tomasz Jeznach
2024-04-18 21:22 ` Robin Murphy
2024-04-24 21:59 ` Tomasz Jeznach
2024-04-25 11:23 ` Robin Murphy
2024-04-18 16:32 ` [PATCH v2 3/7] iommu/riscv: Add RISC-V IOMMU PCIe " Tomasz Jeznach
2024-04-18 22:07 ` Robin Murphy
2024-04-18 16:32 ` [PATCH v2 4/7] iommu/riscv: Enable IOMMU registration and device probe Tomasz Jeznach
2024-04-18 16:32 ` [PATCH v2 5/7] iommu/riscv: Device directory management Tomasz Jeznach
2024-04-19 12:40 ` Jason Gunthorpe
2024-04-24 23:01 ` Tomasz Jeznach
2024-04-24 23:07 ` Jason Gunthorpe [this message]
2024-04-22 5:11 ` Baolu Lu
2024-04-24 23:07 ` Tomasz Jeznach
2024-04-18 16:32 ` [PATCH v2 6/7] iommu/riscv: Command and fault queue support Tomasz Jeznach
2024-04-18 16:32 ` [PATCH v2 7/7] iommu/riscv: Paging domain support Tomasz Jeznach
2024-04-19 12:56 ` Jason Gunthorpe
2024-04-22 7:40 ` Baolu Lu
2024-04-24 23:30 ` Tomasz Jeznach
2024-04-24 23:39 ` Jason Gunthorpe
2024-04-24 23:54 ` Tomasz Jeznach
2024-04-25 0:48 ` Jason Gunthorpe
2024-04-22 5:21 ` Baolu Lu
2024-04-22 19:30 ` Jason Gunthorpe
2024-04-23 17:00 ` Andrew Jones
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