Paolo, Alex, we plan to submit this fixup via Martins s390 tree (as it is all in common s390 memory management). It fixes a fundamental design bug in our page table handling. Some background: Normal page tables are 2kb. For KVM we need a special page table extension that creates another 2k after the page table (pgste). As there are some workloads which have a high page table footprint (e.g. data bases with thousands of processes on shared memory), we want to miminize the impact of the page table extensions to just KVM processes. Now: our approach of replacing the page table on CREATE_VM or ENABLE_SIE has a fundamental race to code that gets page table pointers or ptl locks without holding the pmd lock or page table lock. So here is another approach: Have a sysctl (with a KCONFIG default) that decides if we need 4k page tables or 2k page tables. KVM then needs this sysctl to be set, otherwise CREATE_VM will return EINVAL. Martin Schwidefsky (1): KVM: s390: remove delayed reallocation of page tables for KVM arch/s390/include/asm/mmu.h | 4 +- arch/s390/include/asm/mmu_context.h | 3 +- arch/s390/include/asm/pgalloc.h | 1 + arch/s390/include/asm/pgtable.h | 9 +++ arch/s390/kvm/Kconfig | 16 ++++ arch/s390/mm/pgtable.c | 142 +++++++++++------------------------- 6 files changed, 74 insertions(+), 101 deletions(-) -- 2.3.0 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
