From: David Hildenbrand on gitlab.com https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1023#note_550896188 But tainting raises an interesting question: we already have CONFIG_CMA enabled in ARK for s390x and powerpc: - s390x uses it for vmcp via cmdline parameter "vmcp_cma" under z/VM; it is set as default to 4 MiB via CONFIG_VMCP_CMA_SIZE. - powerpc uses it for KVM via cmdline parameter "kvm_cma_resv_ratio"; this is set as default to 5% of all RAM and applies if the CPU supports hardware virtualization IIUC. So when we taint when activating the regions via mark_tech_preview(), we would taint any kernel running on s390x under z/VM and any kernel running on ppc64 with CPU_FTR_HVMODE. Tainting when actually allocating via CMA sounds a bit better, but we already mess with core-mm when reserving/activating the regions. These features want to use CMA, and we only want to support CMA as tech preview. These features also wouldn't have worked like that on RHEL 8, where we don't have CMA. I see the following alternatives a) Taint only on x86_64. Feels wrong. b) Taint always. Leave the settings unmodified. This will taint some setups always. Bad. c) Taint always. Set vmcp_cma and kvm_cma_resv_ratio as default to 0 in RHEL 9 while CMA is tech preview. c) sounds like the best bet for RHEL 9 while CMA is tech-preview. @ddutile @llong1 @raquini, what's your take? _______________________________________________ kernel mailing list -- kernel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to kernel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/kernel@xxxxxxxxxxxxxxxxxxxxxxx Do not reply to spam on the list, report it: https://pagure.io/fedora-infrastructure
