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Commit df88f318 authored by Janosch Frank's avatar Janosch Frank Committed by Christian Borntraeger
Browse files

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: default avatarJanosch Frank <frankja@linux.ibm.com>
Fixes: a4499382 ("KVM: s390: Add huge page enablement control")
Reviewed-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
parent 204c9724

arch/s390/include/asm/mmu.h

+7 −1
Original line number Diff line number Diff line
@@ -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;

arch/s390/kvm/kvm-s390.c

+2 −0
Original line number Diff line number Diff line
@@ -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