s390/uv: Rework page allocation for guest variable storage area

Alexander Gordeev reported that the allocation of pages of the
guest variable storage area via the uv_alloc_range_cb() callback
of apply_to_page_range() will cause problems as soon as s390 fully
supports lazy mmu mode.

Problem is that uv_alloc_range_cb() allocates pages with GFP_KERNEL while
preemption would be disabled. This would result in reports like this:

 BUG: sleeping function called from invalid context at ./include/linux/sched/mm.h:322
 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 6092, name: qemu-kvm
 preempt_count: 1, expected: 0
...
 Call Trace:
  dump_stack_lvl+0xae/0x108
  __might_resched+0x1de/0x2f0
  prepare_alloc_pages+0x1ba/0x220
  __alloc_frozen_pages_noprof+0xc6/0x390
  alloc_pages_mpol+0xe6/0x220
  alloc_frozen_pages_noprof+0x5c/0x80
  alloc_pages_noprof+0x22/0x80
  uv_alloc_range_cb+0x30/0x300
  apply_to_pte_range+0x11a/0x3b0
  apply_to_pmd_range+0x13a/0x250
  __apply_to_page_range+0x232/0x4d0
  apply_to_page_range+0x28/0x40
  uv_alloc_stor_var+0x5e/0x90
  kvm_s390_pv_alloc_vm+0x118/0x1e0 [kvm]
  kvm_s390_pv_init_vm+0x84/0x2e0 [kvm]
  kvm_s390_handle_pv+0x502/0xf70 [kvm]
  kvm_arch_vm_ioctl+0x234/0xdd0 [kvm]
  kvm_vm_ioctl+0x33a/0x890 [kvm]
  __s390x_sys_ioctl+0xfa/0x130
  __do_syscall+0x1fc/0x700
  system_call+0x72/0x90

Preallocate the pages and make use of vm_area_map_pages() to address this
potential future bug.

Reported-by: Alexander Gordeev <agordeev@linux.ibm.com>
Closes: https://lore.kernel.org/all/e9449c63-b8d2-4ed9-a184-7dcab3e8dfce-agordeev@linux.ibm.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>

0 files changed, 0 insertions, 0 deletions