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Thu, 16 Sep 2021 09:26:14 +0100 From: Shameerali Kolothum Thodi To: Jon Nettleton Subject: RE: [PATCH v7 2/9] ACPI/IORT: Add support for RMR node parsing Thread-Topic: [PATCH v7 2/9] ACPI/IORT: Add support for RMR node parsing Thread-Index: AQHXidEiKr58723PTUGGkSglF1QKPatlAmqAgDJmwoCAACN+gIAO55oggAAG1QCAABhrQA== Date: Thu, 16 Sep 2021 08:26:14 +0000 Message-ID: References: <20210805080724.480-1-shameerali.kolothum.thodi@huawei.com> <20210805080724.480-3-shameerali.kolothum.thodi@huawei.com> <20210805160319.GB23085@lpieralisi> <5d9bebdf-6eb5-49a0-2e8f-490df2d6754d@arm.com> In-Reply-To: Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.47.83.177] MIME-Version: 1.0 X-CFilter-Loop: Reflected Cc: Will Deacon , Steven Price , ACPI Devel Maling List , Linux IOMMU , wanghuiqiang , "Guohanjun \(Hanjun Guo\)" , yangyicong , Sami Mujawar , Robin Murphy , linux-arm-kernel X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" > -----Original Message----- > From: Jon Nettleton [mailto:jon@solid-run.com] > Sent: 16 September 2021 08:52 > To: Shameerali Kolothum Thodi > Cc: Robin Murphy ; Lorenzo Pieralisi > ; Laurentiu Tudor ; > linux-arm-kernel ; ACPI Devel Maling > List ; Linux IOMMU > ; Joerg Roedel ; Will > Deacon ; wanghuiqiang ; > Guohanjun (Hanjun Guo) ; Steven Price > ; Sami Mujawar ; Eric > Auger ; yangyicong > Subject: Re: [PATCH v7 2/9] ACPI/IORT: Add support for RMR node parsing > > On Thu, Sep 16, 2021 at 9:26 AM Shameerali Kolothum Thodi > wrote: > > > > > > > > > -----Original Message----- > > > From: Jon Nettleton [mailto:jon@solid-run.com] > > > Sent: 06 September 2021 20:51 > > > To: Robin Murphy > > > Cc: Lorenzo Pieralisi ; Shameerali > > > Kolothum Thodi ; Laurentiu > > > Tudor ; linux-arm-kernel > > > ; ACPI Devel Maling List > > > ; Linux IOMMU > > > ; Linuxarm ; > > > Joerg Roedel ; Will Deacon ; > > > wanghuiqiang ; Guohanjun (Hanjun Guo) > > > ; Steven Price ; Sami > > > Mujawar ; Eric Auger > ; > > > yangyicong > > > Subject: Re: [PATCH v7 2/9] ACPI/IORT: Add support for RMR node > > > parsing > > > > > [...] > > > > > > > > > > > > On the prot value assignment based on the remapping flag, I'd > > > > > like to hear Robin/Joerg's opinion, I'd avoid being in a > > > > > situation where "normally" this would work but then we have to quirk > it. > > > > > > > > > > Is this a valid assumption _always_ ? > > > > > > > > No. Certainly applying IOMMU_CACHE without reference to the > > > > device's _CCA attribute or how CPUs may be accessing a shared > > > > buffer could lead to a loss of coherency. At worst, applying > > > > IOMMU_MMIO to a device-private buffer *could* cause the device to > > > > lose coherency with itself if the memory underlying the RMR may > > > > have allocated into system caches. Note that the expected use for > > > > non-remappable RMRs is the device holding some sort of long-lived > > > > private data in system RAM - the MSI doorbell trick is far more of a niche > hack really. > > > > > > > > At the very least I think we need to refer to the device's memory > > > > access properties here. > > > > > > > > Jon, Laurentiu - how do RMRs correspond to the EFI memory map on > > > > your firmware? I'm starting to think that as long as the > > > > underlying memory is described appropriately there then we should > > > > be able to infer correct attributes from the EFI memory type and flags. > > > > > > The devices are all cache coherent and marked as _CCA, 1. The > > > Memory regions are in the virt table as > ARM_MEMORY_REGION_ATTRIBUTE_DEVICE. > > > > > > The current chicken and egg problem we have is that during the > > > fsl-mc-bus initialization we call > > > > > > error = acpi_dma_configure_id(&pdev->dev, DEV_DMA_COHERENT, > > > &mc_stream_id); > > > > > > which gets deferred because the SMMU has not been initialized yet. > > > Then we initialize the RMR tables but there is no device reference > > > there to be able to query device properties, only the stream id. > > > After the IORT tables are parsed and the SMMU is setup, on the > > > second device probe we associate everything based on the stream id > > > and the fsl-mc-bus device is able to claim its 1-1 DMA mappings. > > > > Can we solve this order problem by delaying the > > iommu_alloc_resv_region() to the iommu_dma_get_rmr_resv_regions(dev, > > list) ? We could invoke > > device_get_dma_attr() from there which I believe will return the _CCA > attribute. > > > > Or is that still early to invoke that? > > That looks like it should work. Do we then also need to parse through the > VirtualMemoryTable matching the start and end addresses to determine the > other memory attributes like MMIO? Yes. But that looks tricky as I can't find that readily available on Arm, like the efi_mem_attributes(). I will take a look. Please let me know if there is one or any other easy way to retrieve it. Thanks, Shameer > > -Jon > > > > > Thanks, > > Shameer > > > > > cat /sys/kernel/iommu_groups/0/reserved_regions > > > 0x0000000001000000 0x0000000010ffffff direct-relaxable > > > 0x0000000008000000 0x00000000080fffff msi > > > 0x000000080c000000 0x000000081bffffff direct-relaxable > > > 0x0000001c00000000 0x0000001c001fffff direct-relaxable > > > 0x0000002080000000 0x000000209fffffff direct-relaxable > > > > > > -Jon > > > > > > > > > > > Robin. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu