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
WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgg@ziepe.ca> To: Tomasz Jeznach <tjeznach@rivosinc.com> Cc: Anup Patel <apatel@ventanamicro.com>, devicetree@vger.kernel.org, Conor Dooley <conor+dt@kernel.org>, Albert Ou <aou@eecs.berkeley.edu>, linux@rivosinc.com, Will Deacon <will@kernel.org>, Joerg Roedel <joro@8bytes.org>, linux-kernel@vger.kernel.org, Rob Herring <robh+dt@kernel.org>, Sebastien Boeuf <seb@rivosinc.com>, iommu@lists.linux.dev, Palmer Dabbelt <palmer@dabbelt.com>, Paul Walmsley <paul.walmsley@sifive.com>, Nick Kossifidis <mick@ics.forth.gr>, Krzysztof Kozlowski <krzk+dt@kernel.org>, Robin Murphy <robin.murphy@arm.com>, linux-riscv@lists.infradead.org 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 _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv
next prev parent reply other threads:[~2024-04-24 23:07 UTC|newest] Thread overview: 60+ 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 ` 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 16:32 ` Tomasz Jeznach 2024-04-18 17:04 ` Conor Dooley 2024-04-18 17:04 ` Conor Dooley 2024-04-24 22:37 ` Tomasz Jeznach 2024-04-24 22:37 ` Tomasz Jeznach 2024-04-25 17:11 ` Conor Dooley 2024-04-25 17:11 ` Conor Dooley 2024-04-22 14:04 ` Rob Herring 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 16:32 ` Tomasz Jeznach 2024-04-18 21:22 ` Robin Murphy 2024-04-18 21:22 ` Robin Murphy 2024-04-24 21:59 ` Tomasz Jeznach 2024-04-24 21:59 ` Tomasz Jeznach 2024-04-25 11:23 ` Robin Murphy 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 16:32 ` Tomasz Jeznach 2024-04-18 22:07 ` Robin Murphy 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 ` Tomasz Jeznach 2024-04-18 16:32 ` [PATCH v2 5/7] iommu/riscv: Device directory management Tomasz Jeznach 2024-04-18 16:32 ` Tomasz Jeznach 2024-04-19 12:40 ` Jason Gunthorpe 2024-04-19 12:40 ` Jason Gunthorpe 2024-04-24 23:01 ` Tomasz Jeznach 2024-04-24 23:01 ` Tomasz Jeznach 2024-04-24 23:07 ` Jason Gunthorpe [this message] 2024-04-24 23:07 ` Jason Gunthorpe 2024-04-22 5:11 ` Baolu Lu 2024-04-22 5:11 ` Baolu Lu 2024-04-24 23:07 ` Tomasz Jeznach 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 ` Tomasz Jeznach 2024-04-18 16:32 ` [PATCH v2 7/7] iommu/riscv: Paging domain support Tomasz Jeznach 2024-04-18 16:32 ` Tomasz Jeznach 2024-04-19 12:56 ` Jason Gunthorpe 2024-04-19 12:56 ` Jason Gunthorpe 2024-04-22 7:40 ` Baolu Lu 2024-04-22 7:40 ` Baolu Lu 2024-04-24 23:30 ` Tomasz Jeznach 2024-04-24 23:30 ` Tomasz Jeznach 2024-04-24 23:39 ` Jason Gunthorpe 2024-04-24 23:39 ` Jason Gunthorpe 2024-04-24 23:54 ` Tomasz Jeznach 2024-04-24 23:54 ` Tomasz Jeznach 2024-04-25 0:48 ` Jason Gunthorpe 2024-04-25 0:48 ` Jason Gunthorpe 2024-04-22 5:21 ` Baolu Lu 2024-04-22 5:21 ` Baolu Lu 2024-04-22 19:30 ` Jason Gunthorpe 2024-04-22 19:30 ` Jason Gunthorpe 2024-04-23 17:00 ` Andrew Jones 2024-04-23 17:00 ` Andrew Jones
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