linux-kernel - [PATCH] iommu/vt-d: Increase DMAR_UNITS

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Date:   Thu,  5 May 2022 14:46:58 -0500
From:   Steve Wahl <steve.wahl@....com>
To:     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
Cc:     Mike Travis <mike.travis@....com>,
        Dimitri Sivanich <sivanich@....com>,
        Steve Wahl <steve.wahl@....com>,
        Russ Anderson <russ.anderson@....com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] iommu/vt-d: Increase DMAR_UNITS_SUPPORTED

Increase DMAR_UNITS_SUPPORTED to support 64 sockets with 10 DMAR units
each, for a total of 640.

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.

Signed-off-by: Steve Wahl <steve.wahl@....com>
Reviewed-by: Mike Travis <mike.travis@....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.

 include/linux/dmar.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/dmar.h b/include/linux/dmar.h
index 45e903d84733..9d4867b8f42e 100644
--- a/include/linux/dmar.h
+++ b/include/linux/dmar.h
@@ -19,7 +19,7 @@
 struct acpi_dmar_header;

 #ifdef	CONFIG_X86
-# define	DMAR_UNITS_SUPPORTED	MAX_IO_APICS
+# define	DMAR_UNITS_SUPPORTED	640
 #else
 # define	DMAR_UNITS_SUPPORTED	64
 #endif
-- 
2.26.2