From: Dominik Dingel <dingel@xxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Cornelia Huck <cornelia.huck@xxxxxxxxxx>
Signed-off-by: Dominik Dingel <dingel@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
---
Documentation/virtual/kvm/devices/vm.txt | 3 ++-
arch/s390/include/asm/kvm_host.h | 1 +
arch/s390/include/uapi/asm/kvm.h | 2 ++
arch/s390/kvm/kvm-s390.c | 25 ++++++++++++++++++++-----
arch/s390/mm/pgtable.c | 4 ++--
5 files changed, 27 insertions(+), 8 deletions(-)
diff --git a/Documentation/virtual/kvm/devices/vm.txt b/Documentation/virtual/kvm/devices/vm.txt
index 2d09d1e..f083a16 100644
--- a/Documentation/virtual/kvm/devices/vm.txt
+++ b/Documentation/virtual/kvm/devices/vm.txt
@@ -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
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 12e9291..c831441 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -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;
diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
index ef1a5fc..d2aea31 100644
--- a/arch/s390/include/uapi/asm/kvm.h
+++ b/arch/s390/include/uapi/asm/kvm.h
@@ -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
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index c14845c..8aa5e55 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -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;
}
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 54ef3bc..63b0398 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -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;
--
2.3.0
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