Messages in this thread | | | Date | Thu, 23 Jun 2022 10:29:35 +0800 | Subject | Re: [PATCH v3] iommu/vt-d: Make DMAR_UNITS_SUPPORTED a config setting | From | Baolu Lu <> |
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On 2022/6/22 23:05, Jerry Snitselaar wrote: > On Wed, Jun 22, 2022 at 7:52 AM Baolu Lu<baolu.lu@linux.intel.com> wrote: >> On 2022/6/16 02:36, Steve Wahl wrote: >>> To support up to 64 sockets with 10 DMAR units each (640), make the >>> value of DMAR_UNITS_SUPPORTED adjustable by a config variable, >>> CONFIG_DMAR_UNITS_SUPPORTED, and make it's default 1024 when MAXSMP is >>> set. >>> >>> If the available hardware exceeds DMAR_UNITS_SUPPORTED (previously set >>> to MAX_IO_APICS, or 128), it causes these messages: "DMAR: Failed to >>> allocate seq_id", "DMAR: Parse DMAR table failure.", and "x2apic: IRQ >>> remapping doesn't support X2APIC mode x2apic disabled"; and the system >>> fails to boot properly. >>> >>> Signed-off-by: Steve Wahl<steve.wahl@hpe.com> >>> Reviewed-by: Kevin Tian<kevin.tian@intel.com> >>> --- >>> >>> Note that we could not find a reason for connecting >>> DMAR_UNITS_SUPPORTED to MAX_IO_APICS as was done previously. Perhaps >>> it seemed like the two would continue to match on earlier processors. >>> There doesn't appear to be kernel code that assumes that the value of >>> one is related to the other. >>> >>> v2: Make this value a config option, rather than a fixed constant. The default >>> values should match previous configuration except in the MAXSMP case. Keeping the >>> value at a power of two was requested by Kevin Tian. >>> >>> v3: Make the config option dependent upon DMAR_TABLE, as it is not used without this. >>> >>> drivers/iommu/intel/Kconfig | 7 +++++++ >>> include/linux/dmar.h | 6 +----- >>> 2 files changed, 8 insertions(+), 5 deletions(-) >>> >>> diff --git a/drivers/iommu/intel/Kconfig b/drivers/iommu/intel/Kconfig >>> index 39a06d245f12..07aaebcb581d 100644 >>> --- a/drivers/iommu/intel/Kconfig >>> +++ b/drivers/iommu/intel/Kconfig >>> @@ -9,6 +9,13 @@ config DMAR_PERF >>> config DMAR_DEBUG >>> bool >>> >>> +config DMAR_UNITS_SUPPORTED >>> + int "Number of DMA Remapping Units supported" >>> + depends on DMAR_TABLE >>> + default 1024 if MAXSMP >>> + default 128 if X86_64 >>> + default 64 >> With this patch applied, the IOMMU configuration looks like: >> >> [*] AMD IOMMU support >> <M> AMD IOMMU Version 2 driver >> [*] Enable AMD IOMMU internals in DebugFS >> (1024) Number of DMA Remapping Units supported <<<< NEW >> [*] Support for Intel IOMMU using DMA Remapping Devices >> [*] Export Intel IOMMU internals in Debugfs >> [*] Support for Shared Virtual Memory with Intel IOMMU >> [*] Enable Intel DMA Remapping Devices by default >> [*] Enable Intel IOMMU scalable mode by default >> [*] Support for Interrupt Remapping >> [*] OMAP IOMMU Support >> [*] Export OMAP IOMMU internals in DebugFS >> [*] Rockchip IOMMU Support >> >> The NEW item looks confusing. It looks to be a generic configurable >> value though it's actually Intel DMAR specific. Any thoughts? >> >> Best regards, >> baolu >> > Would moving it under INTEL_IOMMU at least have it show up below > "Support for Intel IOMMU using DMA Remapping Devices"? I'm not sure it > can be better than that, because IRQ_REMAP selects DMAR_TABLE, so we > can't stick it in the if INTEL_IOMMU section.
It's more reasonable to move it under INTEL_IOMMU, but the trouble is that this also stands even if INTEL_IOMMU is not configured.
The real problem here is that the iommu sequence ID overflows if DMAR_UNITS_SUPPORTED is not big enough. This is purely a software implementation issue, I am not sure whether user opt-in when building a kernel package could help a lot here.
If we can't find a better way, can we just step back?
Best regards, baolu
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