53c4ab70c1
git commit badb8bb983e9 "fix alloc_pgste check in init_new_context" fixed
the problem of 'current->mm == NULL' in init_new_context back in 2011.
git commit 3eabaee998c7 "KVM: s390: allow sie enablement for multi-
threaded programs" completely removed the check against alloc_pgste.
git commit 23fefe119ceb "s390/kvm: avoid global config of vm.alloc_pgste=1"
re-added a check against the alloc_pgste flag but without the required
check for current->mm != NULL.
For execve() called by a kernel thread init_new_context() reads from
((struct mm_struct *) NULL)->context.alloc_pgste to decide between
2K vs 4K page tables. If the bit happens to be set for the init process
it will be created with large page tables. This decision is inherited by
all the children of init, this waste quite some memory.
Re-add the check for 'current->mm != NULL'.
Fixes: 23fefe119ceb ("s390/kvm: avoid global config of vm.alloc_pgste=1")
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.