Commit a3a92c31 authored by Dominik Dingel's avatar Dominik Dingel Committed by Christian Borntraeger
Browse files

KVM: s390: fix mismatch between user and in-kernel guest limit 



While the userspace interface requests the maximum size the gmap code
expects to get a maximum address.

This error resulted in bigger page tables than necessary for some guest
sizes, e.g. a 2GB guest used 3 levels instead of 2.

At the same time we introduce KVM_S390_NO_MEM_LIMIT, which allows in a
bright future that a guest spans the complete 64 bit address space.

We also switch to TASK_MAX_SIZE for the initial memory size, this is a
cosmetic change as the previous size also resulted in a 4 level pagetable
creation.

Reported-by: default avatarDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: default avatarCornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: default avatarDominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
parent 8335713a

Documentation/virtual/kvm/devices/vm.txt

+2 −1
Original line number Diff line number Diff line
@@ -37,7 +37,8 @@ Returns: -EFAULT if the given address is not accessible 
Allows userspace to query the actual limit and set a new limit for

the maximum guest memory size. The limit will be rounded up to

2048 MB, 4096 GB, 8192 TB respectively, as this limit is governed by

the number of page table levels.

the number of page table levels. In the case that there is no limit we will set

the limit to KVM_S390_NO_MEM_LIMIT (U64_MAX).



2. GROUP: KVM_S390_VM_CPU_MODEL

Architectures: s390

arch/s390/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -627,6 +627,7 @@ struct kvm_arch{ 
	struct kvm_s390_float_interrupt float_int;

	struct kvm_device *flic;

	struct gmap *gmap;

	unsigned long mem_limit;

	int css_support;

	int use_irqchip;

	int use_cmma;

arch/s390/include/uapi/asm/kvm.h

+2 −0
Original line number Diff line number Diff line
@@ -66,6 +66,8 @@ struct kvm_s390_io_adapter_req { 
#define KVM_S390_VM_MEM_CLR_CMMA	1

#define KVM_S390_VM_MEM_LIMIT_SIZE	2



#define KVM_S390_NO_MEM_LIMIT		U64_MAX



/* kvm attributes for KVM_S390_VM_TOD */

#define KVM_S390_VM_TOD_LOW		0

#define KVM_S390_VM_TOD_HIGH		1

arch/s390/kvm/kvm-s390.c

+20 −5
Original line number Diff line number Diff line
@@ -378,8 +378,8 @@ static int kvm_s390_get_mem_control(struct kvm *kvm, struct kvm_device_attr *att 
	case KVM_S390_VM_MEM_LIMIT_SIZE:

		ret = 0;

		VM_EVENT(kvm, 3, "QUERY: max guest memory: %lu bytes",

			 kvm->arch.gmap->asce_end);

		if (put_user(kvm->arch.gmap->asce_end, (u64 __user *)attr->addr))

			 kvm->arch.mem_limit);

		if (put_user(kvm->arch.mem_limit, (u64 __user *)attr->addr))

			ret = -EFAULT;

		break;

	default:
@@ -431,9 +431,17 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att 
		if (get_user(new_limit, (u64 __user *)attr->addr))

			return -EFAULT;



		if (new_limit > kvm->arch.gmap->asce_end)

		if (kvm->arch.mem_limit != KVM_S390_NO_MEM_LIMIT &&

		    new_limit > kvm->arch.mem_limit)

			return -E2BIG;



		if (!new_limit)

			return -EINVAL;



		/* gmap_alloc takes last usable address */

		if (new_limit != KVM_S390_NO_MEM_LIMIT)

			new_limit -= 1;



		ret = -EBUSY;

		mutex_lock(&kvm->lock);

		if (atomic_read(&kvm->online_vcpus) == 0) {
@@ -450,7 +458,9 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att 
			}

		}

		mutex_unlock(&kvm->lock);

		VM_EVENT(kvm, 3, "SET: max guest memory: %lu bytes", new_limit);

		VM_EVENT(kvm, 3, "SET: max guest address: %lu", new_limit);

		VM_EVENT(kvm, 3, "New guest asce: 0x%pK",

			 (void *) kvm->arch.gmap->asce);

		break;

	}

	default:
@@ -1172,8 +1182,10 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) 


	if (type & KVM_VM_S390_UCONTROL) {

		kvm->arch.gmap = NULL;

		kvm->arch.mem_limit = KVM_S390_NO_MEM_LIMIT;

	} else {

		kvm->arch.gmap = gmap_alloc(current->mm, (1UL << 44) - 1);

		kvm->arch.mem_limit = TASK_MAX_SIZE;

		kvm->arch.gmap = gmap_alloc(current->mm, kvm->arch.mem_limit - 1);

		if (!kvm->arch.gmap)

			goto out_err;

		kvm->arch.gmap->private = kvm;
@@ -2829,6 +2841,9 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, 
	if (mem->memory_size & 0xffffful)

		return -EINVAL;



	if (mem->guest_phys_addr + mem->memory_size > kvm->arch.mem_limit)

		return -EINVAL;



	return 0;

}

arch/s390/mm/pgtable.c

+2 −2
Original line number Diff line number Diff line
@@ -133,7 +133,7 @@ void crst_table_downgrade(struct mm_struct *mm, unsigned long limit) 
/**

 * gmap_alloc - allocate a guest address space

 * @mm: pointer to the parent mm_struct

 * @limit: maximum size of the gmap address space

 * @limit: maximum address of the gmap address space

 *

 * Returns a guest address space structure.

 */
@@ -402,7 +402,7 @@ int gmap_map_segment(struct gmap *gmap, unsigned long from, 
	if ((from | to | len) & (PMD_SIZE - 1))

		return -EINVAL;

	if (len == 0 || from + len < from || to + len < to ||

	    from + len > TASK_MAX_SIZE || to + len > gmap->asce_end)

	    from + len - 1 > TASK_MAX_SIZE || to + len - 1 > gmap->asce_end)

		return -EINVAL;



	flush = 0;

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