mbox series

[SRU,j:linux-gcp-6.8,v2,0/1] Enable IOMMU Passthrough by default

Message ID 20241105162833.15921-1-ian.whitfield@canonical.com
Headers show
Series Enable IOMMU Passthrough by default | expand

Message

Ian Whitfield Nov. 5, 2024, 4:28 p.m. UTC 
[Impact]

C3 bare metal instances run into a problem on 6.8 kernels due to Intel
IOMMU being enabled by default. After performing enough disk-intensive
work on the instance, the system becomes unusable and reports I/O
errors at the command line until rebooted, losing data in the process.
The root issue is being worked on long-term, but in the meantime we
will apply a workaround to the issue for affected customers. This fix
has a negative impact on security, so it is limited to Jammy kernels
for which this issue is a regression. Noble kernels have always had
this problem and therefore will be waiting for the long-term fix.

[Fix]

Change the kernel config to use IOMMU passthrough by default.

[Test Plan]

Perform up to 50 kernel builds on the instance in sequence. Failures on
affected instances are usually detected after only 1 or 2.

[Regression potential]

Regression potential is especially low for Jammy as we are essentially
reverting a breaking change.

v2: Fixed subject line (was j:linux-gcp)

Ian Whitfield (1):
  UBUNTU: gcp: Enable IOMMU Passthrough by default

 debian.gcp-6.8/config/annotations | 9 +++++++++
 1 file changed, 9 insertions(+)

Comments

Philip Cox Nov. 5, 2024, 5:17 p.m. UTC | #1 
On 2024-11-05 11:28 a.m., Ian Whitfield wrote:
> [Impact]
>
> C3 bare metal instances run into a problem on 6.8 kernels due to Intel
> IOMMU being enabled by default. After performing enough disk-intensive
> work on the instance, the system becomes unusable and reports I/O
> errors at the command line until rebooted, losing data in the process.
> The root issue is being worked on long-term, but in the meantime we
> will apply a workaround to the issue for affected customers. This fix
> has a negative impact on security, so it is limited to Jammy kernels
> for which this issue is a regression. Noble kernels have always had
> this problem and therefore will be waiting for the long-term fix.
>
> [Fix]
>
> Change the kernel config to use IOMMU passthrough by default.
>
> [Test Plan]
>
> Perform up to 50 kernel builds on the instance in sequence. Failures on
> affected instances are usually detected after only 1 or 2.
>
> [Regression potential]
>
> Regression potential is especially low for Jammy as we are essentially
> reverting a breaking change.
>
> v2: Fixed subject line (was j:linux-gcp)
>
> Ian Whitfield (1):
>    UBUNTU: gcp: Enable IOMMU Passthrough by default

Acked-By: Philip Cox <philip.cox@canonical.com>




>   debian.gcp-6.8/config/annotations | 9 +++++++++
>   1 file changed, 9 insertions(+)
>