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authorXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>2012-08-21 11:02:51 +0800
committerAvi Kivity <avi@redhat.com>2012-08-22 15:09:03 +0300
commit4d8b81abc47b83a1939e59df2fdb0e98dfe0eedd (patch)
tree47ea77cb4f77a2884a0478ecf84f62e32e5661ee /virt
parent7068d0971524dd47a38f44f6020ba133432871ca (diff)
downloadvexpress-lsk-4d8b81abc47b83a1939e59df2fdb0e98dfe0eedd.tar.gz
KVM: introduce readonly memslot
In current code, if we map a readonly memory space from host to guest and the page is not currently mapped in the host, we will get a fault pfn and async is not allowed, then the vm will crash We introduce readonly memory region to map ROM/ROMD to the guest, read access is happy for readonly memslot, write access on readonly memslot will cause KVM_EXIT_MMIO exit Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/kvm_main.c96
1 files changed, 78 insertions, 18 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e3e1658c491..3416f8a31f6 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -680,7 +680,13 @@ void update_memslots(struct kvm_memslots *slots, struct kvm_memory_slot *new)
static int check_memory_region_flags(struct kvm_userspace_memory_region *mem)
{
- if (mem->flags & ~KVM_MEM_LOG_DIRTY_PAGES)
+ u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;
+
+#ifdef KVM_CAP_READONLY_MEM
+ valid_flags |= KVM_MEM_READONLY;
+#endif
+
+ if (mem->flags & ~valid_flags)
return -EINVAL;
return 0;
@@ -973,18 +979,45 @@ out:
return size;
}
-static unsigned long gfn_to_hva_many(struct kvm_memory_slot *slot, gfn_t gfn,
- gfn_t *nr_pages)
+static bool memslot_is_readonly(struct kvm_memory_slot *slot)
+{
+ return slot->flags & KVM_MEM_READONLY;
+}
+
+static unsigned long __gfn_to_hva_memslot(struct kvm_memory_slot *slot,
+ gfn_t gfn)
+{
+ return slot->userspace_addr + (gfn - slot->base_gfn) * PAGE_SIZE;
+}
+
+static unsigned long __gfn_to_hva_many(struct kvm_memory_slot *slot, gfn_t gfn,
+ gfn_t *nr_pages, bool write)
{
if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
return KVM_HVA_ERR_BAD;
+ if (memslot_is_readonly(slot) && write)
+ return KVM_HVA_ERR_RO_BAD;
+
if (nr_pages)
*nr_pages = slot->npages - (gfn - slot->base_gfn);
- return gfn_to_hva_memslot(slot, gfn);
+ return __gfn_to_hva_memslot(slot, gfn);
}
+static unsigned long gfn_to_hva_many(struct kvm_memory_slot *slot, gfn_t gfn,
+ gfn_t *nr_pages)
+{
+ return __gfn_to_hva_many(slot, gfn, nr_pages, true);
+}
+
+unsigned long gfn_to_hva_memslot(struct kvm_memory_slot *slot,
+ gfn_t gfn)
+{
+ return gfn_to_hva_many(slot, gfn, NULL);
+}
+EXPORT_SYMBOL_GPL(gfn_to_hva_memslot);
+
unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
{
return gfn_to_hva_many(gfn_to_memslot(kvm, gfn), gfn, NULL);
@@ -997,7 +1030,7 @@ EXPORT_SYMBOL_GPL(gfn_to_hva);
*/
static unsigned long gfn_to_hva_read(struct kvm *kvm, gfn_t gfn)
{
- return gfn_to_hva_many(gfn_to_memslot(kvm, gfn), gfn, NULL);
+ return __gfn_to_hva_many(gfn_to_memslot(kvm, gfn), gfn, NULL, false);
}
static int kvm_read_hva(void *data, void __user *hva, int len)
@@ -1106,6 +1139,17 @@ static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault,
return npages;
}
+static bool vma_is_valid(struct vm_area_struct *vma, bool write_fault)
+{
+ if (unlikely(!(vma->vm_flags & VM_READ)))
+ return false;
+
+ if (write_fault && (unlikely(!(vma->vm_flags & VM_WRITE))))
+ return false;
+
+ return true;
+}
+
/*
* Pin guest page in memory and return its pfn.
* @addr: host virtual address which maps memory to the guest
@@ -1130,8 +1174,6 @@ static pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
/* we can do it either atomically or asynchronously, not both */
BUG_ON(atomic && async);
- BUG_ON(!write_fault && !writable);
-
if (hva_to_pfn_fast(addr, atomic, async, write_fault, writable, &pfn))
return pfn;
@@ -1158,7 +1200,7 @@ static pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
vma->vm_pgoff;
BUG_ON(!kvm_is_mmio_pfn(pfn));
} else {
- if (async && (vma->vm_flags & VM_WRITE))
+ if (async && vma_is_valid(vma, write_fault))
*async = true;
pfn = KVM_PFN_ERR_FAULT;
}
@@ -1167,19 +1209,40 @@ exit:
return pfn;
}
+static pfn_t
+__gfn_to_pfn_memslot(struct kvm_memory_slot *slot, gfn_t gfn, bool atomic,
+ bool *async, bool write_fault, bool *writable)
+{
+ unsigned long addr = __gfn_to_hva_many(slot, gfn, NULL, write_fault);
+
+ if (addr == KVM_HVA_ERR_RO_BAD)
+ return KVM_PFN_ERR_RO_FAULT;
+
+ if (kvm_is_error_hva(addr))
+ return KVM_PFN_ERR_BAD;
+
+ /* Do not map writable pfn in the readonly memslot. */
+ if (writable && memslot_is_readonly(slot)) {
+ *writable = false;
+ writable = NULL;
+ }
+
+ return hva_to_pfn(addr, atomic, async, write_fault,
+ writable);
+}
+
static pfn_t __gfn_to_pfn(struct kvm *kvm, gfn_t gfn, bool atomic, bool *async,
bool write_fault, bool *writable)
{
- unsigned long addr;
+ struct kvm_memory_slot *slot;
if (async)
*async = false;
- addr = gfn_to_hva(kvm, gfn);
- if (kvm_is_error_hva(addr))
- return KVM_PFN_ERR_BAD;
+ slot = gfn_to_memslot(kvm, gfn);
- return hva_to_pfn(addr, atomic, async, write_fault, writable);
+ return __gfn_to_pfn_memslot(slot, gfn, atomic, async, write_fault,
+ writable);
}
pfn_t gfn_to_pfn_atomic(struct kvm *kvm, gfn_t gfn)
@@ -1210,15 +1273,12 @@ EXPORT_SYMBOL_GPL(gfn_to_pfn_prot);
pfn_t gfn_to_pfn_memslot(struct kvm_memory_slot *slot, gfn_t gfn)
{
- unsigned long addr = gfn_to_hva_memslot(slot, gfn);
- return hva_to_pfn(addr, false, NULL, true, NULL);
+ return __gfn_to_pfn_memslot(slot, gfn, false, NULL, true, NULL);
}
pfn_t gfn_to_pfn_memslot_atomic(struct kvm_memory_slot *slot, gfn_t gfn)
{
- unsigned long addr = gfn_to_hva_memslot(slot, gfn);
-
- return hva_to_pfn(addr, true, NULL, true, NULL);
+ return __gfn_to_pfn_memslot(slot, gfn, true, NULL, true, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_pfn_memslot_atomic);