ACK: [PATCH 1/1] PCI: vmd: Do not disable MSI-X remapping if interrupt remapping is enabled by IOMMU

[Krzysztof Kozlowski]

On 16/02/2022 06:01, Jeff Lane wrote:
> From: Adrian Huang <ahuang12 at lenovo.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1937295
> 
> When enabling VMD in BIOS setup (Ice Lake Processor: Whitley platform),
> the host OS cannot boot successfully with the following error message:
> 
>   nvme nvme0: I/O 12 QID 0 timeout, completion polled
>   nvme nvme0: Shutdown timeout set to 6 seconds
>   DMAR: DRHD: handling fault status reg 2
>   DMAR: [INTR-REMAP] Request device [0x00:0x00.5] fault index 0xa00 [fault reason 0x25] Blocked a compatibility format interrupt request
> 
> The request device is the VMD controller:
>   # lspci -s 0000:00.5 -nn
>   0000:00:00.5 RAID bus controller [0104]: Intel Corporation Volume
>   Management Device NVMe RAID Controller [8086:28c0] (rev 04)
> 
> `git bisect` points to this offending commit ee81ee84f873 ("PCI:
> vmd: Disable MSI-X remapping when possible"), which disables VMD MSI
> remapping. The IOMMU hardware blocks the compatibility format
> interrupt request because Interrupt Remapping Enable Status (IRES) and
> Extended Interrupt Mode Enable (EIME) are enabled. Please refer to
> section "5.1.4 Interrupt-Remapping Hardware Operation" in Intel VT-d
> spec.
> 
> To fix the issue, VMD driver still enables the interrupt remapping
> irrespective of VMD_FEAT_CAN_BYPASS_MSI_REMAP if the IOMMU subsystem
> enables the interrupt remapping.
> 
> Test configuration is shown as follows:
>   * Two VMD controllers
>     1. 8086:28c0 (Whitley's VMD)
>     2. 8086:201d (Purley's VMD: The issue does not appear in this
>        controller. Just make sure if any side effect occurs.)
>   * w/wo intremap=off
> 
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=214219
> Link: https://lore.kernel.org/r/20210901124047.1615-1-adrianhuang0701@gmail.com
> Signed-off-by: Adrian Huang <ahuang12 at lenovo.com>
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> Reviewed-by: Jon Derrick <jonathan.derrick at intel.com>
> Cc: Jon Derrick <jonathan.derrick at intel.com>
> Cc: Nirmal Patel <nirmal.patel at linux.intel.com>
> Cc: Joerg Roedel <jroedel at suse.de>
> (cherry picked from commit 2565e5b69c44b4e42469afea3cc5a97e74d1ed45)
> Signed-off-by: Jeff Lane <jeffrey.lane at canonical.com>
> ---
>  drivers/pci/controller/vmd.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski at canonical.com>


Best regards,
Krzysztof