------- Comment From leona...@ibm.com 2019-03-14 15:47 EDT------- Patchset SRU
[Impact] * VMs have a high chance to hit guest migration issues if more than one guest migration happens at a time, while using THP on ppc64le. * Migrating VMs in parallel will cause at least one guest to crash about half the time. Since VM migration is a upgrade/uptime strategy this has a fairly large customer impact. * The uploaded patches correct the behavior of THP on guests. They are available on v4.18.x onwards. [Test Case] * One can reproduce the bug by trying two guest migrations, at the same time, following this instructions on comment 12: https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1788098/comments/12 [Regression Potential] * These patches are already on linux-stable since v4.18.15 (also on hwe), so there is low regression chance. 8afc7da95a7e [Bionic] KVM: PPC: Book3S HV: Avoid crash from THP collapse during radix page fault 82f7758a9c99 [Bionic] KVM: PPC: Book3S HV: Don't use compound_order to determine host mapping size b0f7664dc993 [Bionic] KVM: PPC: Book3S HV: Use correct pagesize in kvm_unmap_radix() 1991612ab005 [Bionic] KVM: PPC: Book3S HV: radix: Do not clear partition PTE when RC or write bits do not match 04fea11aa5fe [Bionic] KVM: PPC: Book3S HV: radix: Refine IO region partition scope attributes 9037e89d8093 [Bionic] KVM: PPC: Book3S HV: Make radix handle process scoped LPID flush in C, with relocation on ed0a86a433c7 [Bionic] KVM: PPC: Book3S HV: Make radix use the Linux translation flush functions for partition scope 0effe5dc3cf4 [Bionic] KVM: PPC: Book3S HV: Recursively unmap all page table entries when unmapping 42cbaef5361b [Bionic] KVM: PPC: Book3S HV: Use a helper to unmap ptes in the radix fault path 414207e08540 [Bionic] powerpc/mm/radix: implement LPID based TLB flushes to be used by KVM eb2a70df7099 [Bionic] powerpc/mm/radix: Remove unused code ad052e60a417 [Bionic] powerpc/kvm: Switch kvm pmd allocator to custom allocator bb2c03e387f4 [Bionic] KVM: PPC: Book 3S HV: Do ptesync in radix guest exit path 699642e0a4f8 [Bionic] KVM: PPC: Book3S HV: Make radix clear pte when unmapping 297755f60b17 [Bionic] KVM: PPC: Book3S HV: Make radix use correct tlbie sequence in kvmppc_radix_tlbie_page d5f5570b7df4 [Bionic] KVM: PPC: Book3S HV: Use __gfn_to_pfn_memslot() in page fault handler b0adb3223100 [Bionic] KVM: PPC: Book3S HV: Handle 1GB pages in radix page fault handler 5be468e7408b [Bionic] KVM: PPC: Book3S HV: Streamline setting of reference and change bits 860816ea1680 [Bionic] KVM: PPC: Book3S HV: Radix page fault handler optimizations 7fe24f427a09 [Bionic] KVM: PPC: Remove unused kvm_unmap_hva callback -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1788098 Title: Avoid migration issues with aligned 2MB THB Status in The Ubuntu-power-systems project: Confirmed Status in linux package in Ubuntu: Confirmed Status in qemu package in Ubuntu: Invalid Status in linux source package in Bionic: Confirmed Status in linux source package in Cosmic: Invalid Bug description: FYI: This blocks bug 1781526 - once this one here is resolved we can go on with SRU considerations for 1781526 ------- Comment From jhop...@us.ibm.com 2018-08-20 17:12 EDT------- Hi, in some environments it was observed that this qemu patch to enable THP made it more likely to hit guest migration issues, however the following kernel patch resolves those migration issues: https://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc.git/commit/?h=kvm-ppc-next&id=c066fafc595eef5ae3c83ae3a8305956b8c3ef15 KVM: PPC: Book3S HV: Use correct pagesize in kvm_unmap_radix() Once merged upstream, it would be good to include that change as well to avoid potential migration problems. Should I open a new bug for that or is it better to track here? Note Paelzer: I have not seen related migration issues myself, but it seems reasonable and confirmed by IBM. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-power-systems/+bug/1788098/+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
