ACK/cmnt: [Patch 0/2 v2] [impish/linux-azure] Azure: not enough RAM under 4GB for CVM

[Tim Gardner]

On 4/4/22 10:45, Bartlomiej Zolnierkiewicz wrote:
> Acked-by: Bartlomiej Zolnierkiewicz <bartlomiej.zolnierkiewicz at canonical.com>
> 
> This is under the assumption that the Azure host doesn't provide (on
> any instance) devices with the addressing limitations which would
> require a 4G limited swiotlb buffer.
> 
> Also it seems that the patch #2 should have "UBUNTU: SAUCE: azure:" in
> the patch subject (just like it is present in the patch #1).
> 

Yup - I'll fix that at application time.

rtg

> On Mon, Apr 4, 2022 at 3:17 PM Tim Gardner <tim.gardner at canonical.com> wrote:
>>
>> v2 - attach the 2nd patch which was forgotten the first time.
>>
>> SRU Justification
>>
>> [Impact]
>> Can you please include one more patchset for the "no enough RAM under 4GB" issue
>> for the v5.13 kernel (and v5.15 kernel):
>> https://lwn.net/ml/linux-kernel/20220209122302.213882-2-ltykernel@gmail.com/
>> https://lwn.net/ml/linux-kernel/20220209122302.213882-3-ltykernel@gmail.com/
>>
>> Without the two patches, currently the 5.13 kernel (and 5.15 kernel) can't boot
>> as a CVM guest on Azure. :-(
>>
>> The background is: currently an Azure host only provides about 900 MB memory below
>> the 4GB boundary while the swiotlb code (which is required by the CVM patchset)
>> needs to allocate memory of a size of MIN(1GB, 6% of the total memory). There will
>> be an Azure host update, with which the host will provide about 3GB memory below
>> the 4GB boundary, but we still need to wait a few more weeks to know the ETA.
>> Currently the above two patches can work around the issue from the guest side.
>>
>> [Test Case]
>>
>> Microsoft tested
>>
>> [Where things could go wrong]
>>
>> These patches could affect non-CVM instances.
>>
>> [Other Info]
>>
>> SF: #00323683

-- 
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Tim Gardner
Canonical, Inc