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>

2 files changed, 6 insertions, 7 deletions

diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 2de335d7f63e..d808694673f9 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -106,7 +106,8 @@ struct kvm_userspace_memory_region {
  * other bits are reserved for kvm internal use which are defined in
  * include/linux/kvm_host.h.
  */
-#define KVM_MEM_LOG_DIRTY_PAGES  1UL
+#define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0)
+#define KVM_MEM_READONLY        (1UL << 1)
 
 /* for KVM_IRQ_LINE */
 struct kvm_irq_level {
@@ -621,6 +622,9 @@ struct kvm_ppc_smmu_info {
 #define KVM_CAP_PPC_GET_SMMU_INFO 78
 #define KVM_CAP_S390_COW 79
 #define KVM_CAP_PPC_ALLOC_HTAB 80
+#ifdef __KVM_HAVE_READONLY_MEM
+#define KVM_CAP_READONLY_MEM 81
+#endif
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index a913ac709a9d..5972c9845ddb 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -465,6 +465,7 @@ int gfn_to_page_many_atomic(struct kvm *kvm, gfn_t gfn, struct page **pages,
 
 struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn);
 unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn);
+unsigned long gfn_to_hva_memslot(struct kvm_memory_slot *slot, gfn_t gfn);
 void kvm_release_page_clean(struct page *page);
 void kvm_release_page_dirty(struct page *page);
 void kvm_set_page_dirty(struct page *page);
@@ -792,12 +793,6 @@ hva_to_gfn_memslot(unsigned long hva, struct kvm_memory_slot *slot)
         return slot->base_gfn + gfn_offset;
 }
 
-static inline 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 inline gpa_t gfn_to_gpa(gfn_t gfn)
 {
         return (gpa_t)gfn << PAGE_SHIFT;