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kvm: Force IOMMU remapping on memory slot read-only flag changes

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Memory slot flags can be altered without changing other parameters of
the slot.  The read-only attribute is the only one the IOMMU cares
about, so generate an un-map, re-map when this occurs.  This also
avoid unnecessarily re-mapping the slot when no IOMMU visible changes
are made.

Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
This commit is contained in:
Alex Williamson 2013-01-24 15:04:03 -07:00 committed by Gleb Natapov
parent 3f0c3d0bb2
commit 261874b0d5
1 changed files with 24 additions and 4 deletions
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28
virt/kvm/kvm_main.c
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@ -731,6 +731,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
struct kvm_memory_slot *slot;
struct kvm_memory_slot old, new;
struct kvm_memslots *slots = NULL, *old_memslots;
bool old_iommu_mapped;
r = check_memory_region_flags(mem);
if (r)
@ -772,6 +773,8 @@ int __kvm_set_memory_region(struct kvm *kvm,
new.npages = npages;
new.flags = mem->flags;
old_iommu_mapped = old.npages;
/*
* Disallow changing a memory slot's size or changing anything about
* zero sized slots that doesn't involve making them non-zero.
@ -835,6 +838,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
/* slot was deleted or moved, clear iommu mapping */
kvm_iommu_unmap_pages(kvm, &old);
old_iommu_mapped = false;
/* From this point no new shadow pages pointing to a deleted,
* or moved, memslot will be created.
*
@ -863,11 +867,27 @@ int __kvm_set_memory_region(struct kvm *kvm,
goto out_free;
}
/* map new memory slot into the iommu */
/*
* IOMMU mapping: New slots need to be mapped. Old slots need to be
* un-mapped and re-mapped if their base changes or if flags that the
* iommu cares about change (read-only). Base change unmapping is
* handled above with slot deletion, so we only unmap incompatible
* flags here. Anything else the iommu might care about for existing
* slots (size changes, userspace addr changes) is disallowed above,
* so any other attribute changes getting here can be skipped.
*/
if (npages) {
r = kvm_iommu_map_pages(kvm, &new);
if (r)
goto out_slots;
if (old_iommu_mapped &&
((new.flags ^ old.flags) & KVM_MEM_READONLY)) {
kvm_iommu_unmap_pages(kvm, &old);
old_iommu_mapped = false;
}
if (!old_iommu_mapped) {
r = kvm_iommu_map_pages(kvm, &new);
if (r)
goto out_slots;
}
}
/* actual memory is freed via old in kvm_free_physmem_slot below */