[PATCH 2/3] KVM: pci passthrough un-page-aligned mmio device on machines w/o VT-d

[PATCH 2/3] KVM: pci passthrough un-page-aligned mmio device on machines w/o VT-d

[刘晓建]

KVM doesn't permit the device's iomem size smaller than 1 page. In fact, this is
not necessary. For my via-rhine nic, the size of iomem is only 0x200, but we can
still use pci passthrough.
And, because un-page-aligned iomem is permitted, sanity check should be adjusted
too.
---
diff -uNr kvm-79/kernel/x86/kvm_main.c kvm-79-fixed/kernel/x86/kvm_main.c
--- kvm-79/kernel/x86/kvm_main.c 2008-11-12 20:24:04.000000000 +0800
+++ kvm-79-fixed/kernel/x86/kvm_main.c 2008-12-12 15:56:19.000000000 +0800
 @@ -751,13 +750,16 @@
  struct kvm_memory_slot old, new;
 
  r = -EINVAL;
- /* General sanity checks */
+#if 0
+ /* For some device, their iomem is not page aligned */
  if (mem->memory_size & (PAGE_SIZE - 1))
  goto out;
  if (mem->guest_phys_addr & (PAGE_SIZE - 1))
  goto out;
  if (user_alloc && (mem->userspace_addr & (PAGE_SIZE - 1)))
  goto out;
+#endif
+ /* General sanity checks */
  if (mem->slot >= KVM_MEMORY_SLOTS + KVM_PRIVATE_MEM_SLOTS)
  goto out;
  if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
@@ -765,7 +767,8 @@
 
  memslot = &kvm->memslots[mem->slot];
  base_gfn = mem->guest_phys_addr >> PAGE_SHIFT;
- npages = mem->memory_size >> PAGE_SHIFT;
+ npages = ((mem->guest_phys_addr + mem->memory_size + PAGE_SIZE - 1) >>
PAGE_SHIFT)
+      - (mem->guest_phys_addr >> PAGE_SHIFT);
  if (!npages)
  mem->flags &= ~KVM_MEM_LOG_DIRTY_PAGES;


Xiaojian Liu