On Thu, Sep 16, 2021 at 10:26 AM Shameerali Kolothum Thodi <[email protected]> wrote: > > > > > -----Original Message----- > > From: Jon Nettleton [mailto:[email protected]] > > Sent: 16 September 2021 08:52 > > To: Shameerali Kolothum Thodi <[email protected]> > > Cc: Robin Murphy <[email protected]>; Lorenzo Pieralisi > > <[email protected]>; Laurentiu Tudor <[email protected]>; > > linux-arm-kernel <[email protected]>; ACPI Devel Maling > > List <[email protected]>; Linux IOMMU > > <[email protected]>; Joerg Roedel <[email protected]>; Will > > Deacon <[email protected]>; wanghuiqiang <[email protected]>; > > Guohanjun (Hanjun Guo) <[email protected]>; Steven Price > > <[email protected]>; Sami Mujawar <[email protected]>; Eric > > Auger <[email protected]>; yangyicong <[email protected]> > > 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 > > <[email protected]> wrote: > > > > > > > > > > > > > -----Original Message----- > > > > From: Jon Nettleton [mailto:[email protected]] > > > > Sent: 06 September 2021 20:51 > > > > To: Robin Murphy <[email protected]> > > > > Cc: Lorenzo Pieralisi <[email protected]>; Shameerali > > > > Kolothum Thodi <[email protected]>; Laurentiu > > > > Tudor <[email protected]>; linux-arm-kernel > > > > <[email protected]>; ACPI Devel Maling List > > > > <[email protected]>; Linux IOMMU > > > > <[email protected]>; Linuxarm <[email protected]>; > > > > Joerg Roedel <[email protected]>; Will Deacon <[email protected]>; > > > > wanghuiqiang <[email protected]>; Guohanjun (Hanjun Guo) > > > > <[email protected]>; Steven Price <[email protected]>; Sami > > > > Mujawar <[email protected]>; Eric Auger > > <[email protected]>; > > > > yangyicong <[email protected]> > > > > 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.
maybe we don't need to. Maybe it is enough to just move iommu_alloc_resv_regions and then set the IOMMU_CACHE flag if type = IOMMU_RESV_DIRECT_RELAXABLE and _CCN=1? -Jon > > 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 [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
