** Description changed: [Impact] The option CONFIG_DMA_CMA seems to cause resume problems on the t2.* instance types (Xen). - With this option enabled device drivers are allowed to use the Contiguous Memory Allocator (CMA) for DMA operations. So, drivers can allocate large physically-contiguous blocks of memory, instead of relying on the I/O map or scatter-gather support. - - However, on resume, the memory used by DMA needs to be re-initialized / re-allocated, but it may fail to allocate large chunks of contiguous memory due to the fact that we also need to restore the hibernation image, using more memory and causing a system hang during the resume process. + With this option enabled device drivers are allowed to use the + Contiguous Memory Allocator (CMA) for DMA operations. So, drivers can + allocate large physically-contiguous blocks of memory, instead of + relying on the I/O map or scatter-gather support. + + However, on resume, the memory used by DMA needs to be re-initialized / + re-allocated, but it may fail to allocate large chunks of contiguous + memory due to the fact that we also need to restore the hibernation + image, using more memory and causing a system hang during the resume + process. [Test case] Hibernate / resume any t2.* instance (especially t2.nano, where the problem seems to happen 100% of the times after 2 consecutive hibernate/resume cycles). [Fix] Disable CONFIG_DMA_CMA. NOTE: this option is already disabled in the generic kernel (see LP: #1362261). + With this option disabled the success rate of hibernation on the t2.* + instance types during our tests jumped to 100%. + [Regression potential] It is a .config change, no regression potential except with the fact that disabling this option also disables the module 'etnaviv' (Vivante graphic card), that is not really needed in the aws kernel.
** Description changed: [Impact] The option CONFIG_DMA_CMA seems to cause resume problems on the t2.* instance types (Xen). With this option enabled device drivers are allowed to use the Contiguous Memory Allocator (CMA) for DMA operations. So, drivers can allocate large physically-contiguous blocks of memory, instead of relying on the I/O map or scatter-gather support. However, on resume, the memory used by DMA needs to be re-initialized / re-allocated, but it may fail to allocate large chunks of contiguous memory due to the fact that we also need to restore the hibernation image, using more memory and causing a system hang during the resume process. [Test case] Hibernate / resume any t2.* instance (especially t2.nano, where the problem seems to happen 100% of the times after 2 consecutive hibernate/resume cycles). [Fix] Disable CONFIG_DMA_CMA. NOTE: this option is already disabled in the generic kernel (see LP: #1362261). With this option disabled the success rate of hibernation on the t2.* instance types during our tests jumped to 100%. [Regression potential] - It is a .config change, no regression potential except with the fact - that disabling this option also disables the module 'etnaviv' (Vivante + It is a .config change, no regression potential except for the fact that + disabling this option also disables the module 'etnaviv' (Vivante graphic card), that is not really needed in the aws kernel. ** Description changed: [Impact] - The option CONFIG_DMA_CMA seems to cause resume problems on the t2.* - instance types (Xen). + The option CONFIG_DMA_CMA seems to cause hibernation failures on the + t2.* instance types (Xen). With this option enabled device drivers are allowed to use the Contiguous Memory Allocator (CMA) for DMA operations. So, drivers can allocate large physically-contiguous blocks of memory, instead of relying on the I/O map or scatter-gather support. However, on resume, the memory used by DMA needs to be re-initialized / re-allocated, but it may fail to allocate large chunks of contiguous memory due to the fact that we also need to restore the hibernation image, using more memory and causing a system hang during the resume process. [Test case] Hibernate / resume any t2.* instance (especially t2.nano, where the problem seems to happen 100% of the times after 2 consecutive hibernate/resume cycles). [Fix] Disable CONFIG_DMA_CMA. NOTE: this option is already disabled in the generic kernel (see LP: #1362261). With this option disabled the success rate of hibernation on the t2.* instance types during our tests jumped to 100%. [Regression potential] It is a .config change, no regression potential except for the fact that disabling this option also disables the module 'etnaviv' (Vivante graphic card), that is not really needed in the aws kernel. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux-aws in Ubuntu. https://bugs.launchpad.net/bugs/1879711 Title: aws: disable CONFIG_DMA_CMA Status in linux-aws package in Ubuntu: New Status in linux-aws source package in Focal: New Bug description: [Impact] The option CONFIG_DMA_CMA seems to cause hibernation failures on the t2.* instance types (Xen). With this option enabled device drivers are allowed to use the Contiguous Memory Allocator (CMA) for DMA operations. So, drivers can allocate large physically-contiguous blocks of memory, instead of relying on the I/O map or scatter-gather support. However, on resume, the memory used by DMA needs to be re-initialized / re-allocated, but it may fail to allocate large chunks of contiguous memory due to the fact that we also need to restore the hibernation image, using more memory and causing a system hang during the resume process. [Test case] Hibernate / resume any t2.* instance (especially t2.nano, where the problem seems to happen 100% of the times after 2 consecutive hibernate/resume cycles). [Fix] Disable CONFIG_DMA_CMA. NOTE: this option is already disabled in the generic kernel (see LP: #1362261). With this option disabled the success rate of hibernation on the t2.* instance types during our tests jumped to 100%. [Regression potential] It is a .config change, no regression potential except for the fact that disabling this option also disables the module 'etnaviv' (Vivante graphic card), that is not really needed in the aws kernel. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-aws/+bug/1879711/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
