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Message-ID: <20220615183937.6k3swpax32lsdhkq@cantor>
Date: Wed, 15 Jun 2022 11:39:37 -0700
From: Jerry Snitselaar <jsnitsel@...hat.com>
To: Steve Wahl <steve.wahl@....com>
Cc: Joerg Roedel <jroedel@...e.de>,
Kyung Min Park <kyung.min.park@...el.com>,
Lu Baolu <baolu.lu@...ux.intel.com>,
David Woodhouse <dwmw2@...radead.org>,
Will Deacon <will@...nel.org>,
iommu@...ts.linux-foundation.org,
Kevin Tian <kevin.tian@...el.com>,
Mike Travis <mike.travis@....com>,
Dimitri Sivanich <sivanich@....com>,
Russ Anderson <russ.anderson@....com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] iommu/vt-d: Make DMAR_UNITS_SUPPORTED a config setting
On Wed, Jun 15, 2022 at 01:36:50PM -0500, 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@....com>
> Reviewed-by: Kevin Tian <kevin.tian@...el.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.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
> +
> config INTEL_IOMMU
> bool "Support for Intel IOMMU using DMA Remapping Devices"
> depends on PCI_MSI && ACPI && (X86 || IA64)
> diff --git a/include/linux/dmar.h b/include/linux/dmar.h
> index 45e903d84733..0c03c1845c23 100644
> --- a/include/linux/dmar.h
> +++ b/include/linux/dmar.h
> @@ -18,11 +18,7 @@
>
> struct acpi_dmar_header;
>
> -#ifdef CONFIG_X86
> -# define DMAR_UNITS_SUPPORTED MAX_IO_APICS
> -#else
> -# define DMAR_UNITS_SUPPORTED 64
> -#endif
> +#define DMAR_UNITS_SUPPORTED CONFIG_DMAR_UNITS_SUPPORTED
>
> /* DMAR Flags */
> #define DMAR_INTR_REMAP 0x1
> --
> 2.26.2
>
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