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authorJanosch Frank <frankja@linux.ibm.com>2018-08-30 16:14:18 +0200
committerChristian Borntraeger <borntraeger@de.ibm.com>2018-09-04 11:40:26 +0200
commitdf88f3181f10565c6e3a89eb6f0f9e6afaaf15f1 (patch)
tree5ecdb676fe4a0bc80ffca99703385a239b107c75 /arch
parent204c97245612b6c255edf4e21e24d417c4a0c008 (diff)
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KVM: s390: Properly lock mm context allow_gmap_hpage_1m setting
We have to do down_write on the mm semaphore to set a bitfield in the mm context. Signed-off-by: Janosch Frank <frankja@linux.ibm.com> Fixes: a4499382 ("KVM: s390: Add huge page enablement control") Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/s390/include/asm/mmu.h8
-rw-r--r--arch/s390/kvm/kvm-s390.c2
2 files changed, 9 insertions, 1 deletions
diff --git a/arch/s390/include/asm/mmu.h b/arch/s390/include/asm/mmu.h
index f31a15044c24..a8418e1379eb 100644
--- a/arch/s390/include/asm/mmu.h
+++ b/arch/s390/include/asm/mmu.h
@@ -16,7 +16,13 @@ typedef struct {
unsigned long asce;
unsigned long asce_limit;
unsigned long vdso_base;
- /* The mmu context allocates 4K page tables. */
+ /*
+ * The following bitfields need a down_write on the mm
+ * semaphore when they are written to. As they are only
+ * written once, they can be read without a lock.
+ *
+ * The mmu context allocates 4K page tables.
+ */
unsigned int alloc_pgste:1;
/* The mmu context uses extended page tables. */
unsigned int has_pgste:1;
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 91ad4a9425c0..f69333fd2fa3 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -695,7 +695,9 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
r = -EINVAL;
else {
r = 0;
+ down_write(&kvm->mm->mmap_sem);
kvm->mm->context.allow_gmap_hpage_1m = 1;
+ up_write(&kvm->mm->mmap_sem);
/*
* We might have to create fake 4k page
* tables. To avoid that the hardware works on