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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: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
This commit is contained in:
Dominik Dingel 2014-12-01 17:24:42 +01:00 committed by Christian Borntraeger
parent 8335713ad0
commit a3a92c31bf
5 changed files with 27 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
Documentation/virtual/kvm/devices/vm.txt
View File

@ -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

1
arch/s390/include/asm/kvm_host.h
View File

@ -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;

2
arch/s390/include/uapi/asm/kvm.h
View File

@ -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

25
arch/s390/kvm/kvm-s390.c
View File

@ -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;
}

4
arch/s390/mm/pgtable.c
View File

@ -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;