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[S390] take mmap_sem when walking guest page table 

gmap_fault needs to walk the guest page table. However, parts of
that may change if some other thread does munmap. In that case
gmap_unmap_notifier will also unmap the corresponding parts from
the guest page table. We need to take mmap_sem in order to serialize
these operations.
do_exception now calls __gmap_fault with mmap_sem held which does
not get exported to modules. The exported function, which is called
from KVM, now takes mmap_sem.

Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Carsten Otte 2011-10-30 15:17:02 +01:00 committed by Martin Schwidefsky
parent cc772456ac
commit 499069e1a4
3 changed files with 16 additions and 2 deletions
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1
arch/s390/include/asm/pgtable.h
View File

@ -696,6 +696,7 @@ void gmap_disable(struct gmap *gmap);
int gmap_map_segment(struct gmap *gmap, unsigned long from,
unsigned long to, unsigned long length);
int gmap_unmap_segment(struct gmap *gmap, unsigned long to, unsigned long len);
unsigned long __gmap_fault(unsigned long address, struct gmap *);
unsigned long gmap_fault(unsigned long address, struct gmap *);
/*

2
arch/s390/mm/fault.c
View File

@ -307,7 +307,7 @@ static inline int do_exception(struct pt_regs *regs, int access,
#ifdef CONFIG_PGSTE
if (test_tsk_thread_flag(current, TIF_SIE) && S390_lowcore.gmap) {
address = gmap_fault(address,
address = __gmap_fault(address,
(struct gmap *) S390_lowcore.gmap);
if (address == -EFAULT) {
fault = VM_FAULT_BADMAP;

15
arch/s390/mm/pgtable.c
View File

@ -393,7 +393,10 @@ out_unmap:
}
EXPORT_SYMBOL_GPL(gmap_map_segment);
unsigned long gmap_fault(unsigned long address, struct gmap *gmap)
/*
* this function is assumed to be called with mmap_sem held
*/
unsigned long __gmap_fault(unsigned long address, struct gmap *gmap)
{
unsigned long *table, vmaddr, segment;
struct mm_struct *mm;
@ -461,7 +464,17 @@ unsigned long gmap_fault(unsigned long address, struct gmap *gmap)
return vmaddr | (address & ~PMD_MASK);
}
return -EFAULT;
}
unsigned long gmap_fault(unsigned long address, struct gmap *gmap)
{
unsigned long rc;
down_read(&gmap->mm->mmap_sem);
rc = __gmap_fault(address, gmap);
up_read(&gmap->mm->mmap_sem);
return rc;
}
EXPORT_SYMBOL_GPL(gmap_fault);