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x86/PCI: Disable enhanced atomics on AMD NBIO 7.7 and 7.11

Multiple users report data corruption during 64-bit DMA transfers on
systems with AMD NBIO 7.7 and 7.11 controllers.

This occurs when BIOS enables AMD "enhanced atomic operations" on PCIe Root
Ports. When enhanced atomics are enabled, any 64-bit DMA access may be
corrupted.

Disable enhanced atomics using SMN for NBIO 7.7 and 7.11 based models.

Reported-by: Mikael Etienne <mikael1022bzh@gmail.com>
Closes: https://lore.kernel.org/178789300872.392066.15963676631650361573@gmail.com/
Reported-by: Arthur Husband <artmoty@gmail.com>
Closes: https://lore.kernel.org/20260406222335.379935-1-artmoty@gmail.com/
Reported-by: Alvin Lim <alvinwylim@gmail.com>
Closes: https://lore.kernel.org/20260621100844.1224301-1-alvinwylim@gmail.com/
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
[bhelgaas: commit log, s/IOVA/DMA/ in comment]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org
Cc: David Laight <david.laight.linux@gmail.com>
Cc: John Smith <imjohnsmith4000@gmail.com>
Cc: Lennert Buytenhek <kernel@wantstofly.org>
Cc: Niklas Cassel <cassel@kernel.org>
Cc: Roland Waltersson <roland.waltersson@netinsight.net>
Link: https://patch.msgid.link/20260908190600.226485-2-mario.limonciello@amd.com
M
Mario Limonciello committed
4fde448225123442c5796f54b7a4400e2d3cbaf6
Parent: 8805840
Committed by Bjorn Helgaas <bhelgaas@google.com> on 9/23/2026, 6:42:21 PM