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Subject[PATCH v7 28/29] KVM: Wait 'til the bitter end to initialize the "new" memslot
Date
From: Sean Christopherson <seanjc@google.com>

Initialize the "new" memslot in the !DELETE path only after the various
sanity checks have passed. This will allow a future commit to allocate
@new dynamically without having to copy a memslot, and without having to
deal with freeing @new in error paths and in the "nothing to change" path
that's hiding in the sanity checks.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
---
virt/kvm/kvm_main.c | 37 ++++++++++++++++++++-----------------
1 file changed, 20 insertions(+), 17 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 4cb97b31eac5..627bd689d5ad 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1845,6 +1845,8 @@ int __kvm_set_memory_region(struct kvm *kvm,
struct kvm_memory_slot new;
struct kvm_memslots *slots;
enum kvm_mr_change change;
+ unsigned long npages;
+ gfn_t base_gfn;
int as_id, id;
int r;

@@ -1871,6 +1873,8 @@ int __kvm_set_memory_region(struct kvm *kvm,
return -EINVAL;
if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
return -EINVAL;
+ if ((mem->memory_size >> PAGE_SHIFT) > KVM_MEM_MAX_NR_PAGES)
+ return -EINVAL;

slots = __kvm_memslots(kvm, as_id);

@@ -1894,15 +1898,8 @@ int __kvm_set_memory_region(struct kvm *kvm,
return kvm_set_memslot(kvm, old, &new, KVM_MR_DELETE);
}

- new.as_id = as_id;
- new.id = id;
- new.base_gfn = mem->guest_phys_addr >> PAGE_SHIFT;
- new.npages = mem->memory_size >> PAGE_SHIFT;
- new.flags = mem->flags;
- new.userspace_addr = mem->userspace_addr;
-
- if (new.npages > KVM_MEM_MAX_NR_PAGES)
- return -EINVAL;
+ base_gfn = (mem->guest_phys_addr >> PAGE_SHIFT);
+ npages = (mem->memory_size >> PAGE_SHIFT);

if (!old || !old->npages) {
change = KVM_MR_CREATE;
@@ -1911,27 +1908,33 @@ int __kvm_set_memory_region(struct kvm *kvm,
* To simplify KVM internals, the total number of pages across
* all memslots must fit in an unsigned long.
*/
- if ((kvm->nr_memslot_pages + new.npages) < kvm->nr_memslot_pages)
+ if ((kvm->nr_memslot_pages + npages) < kvm->nr_memslot_pages)
return -EINVAL;
} else { /* Modify an existing slot. */
- if ((new.userspace_addr != old->userspace_addr) ||
- (new.npages != old->npages) ||
- ((new.flags ^ old->flags) & KVM_MEM_READONLY))
+ if ((mem->userspace_addr != old->userspace_addr) ||
+ (npages != old->npages) ||
+ ((mem->flags ^ old->flags) & KVM_MEM_READONLY))
return -EINVAL;

- if (new.base_gfn != old->base_gfn)
+ if (base_gfn != old->base_gfn)
change = KVM_MR_MOVE;
- else if (new.flags != old->flags)
+ else if (mem->flags != old->flags)
change = KVM_MR_FLAGS_ONLY;
else /* Nothing to change. */
return 0;
}

if ((change == KVM_MR_CREATE || change == KVM_MR_MOVE) &&
- kvm_check_memslot_overlap(slots, id, new.base_gfn,
- new.base_gfn + new.npages))
+ kvm_check_memslot_overlap(slots, id, base_gfn, base_gfn + npages))
return -EEXIST;

+ new.as_id = as_id;
+ new.id = id;
+ new.base_gfn = base_gfn;
+ new.npages = npages;
+ new.flags = mem->flags;
+ new.userspace_addr = mem->userspace_addr;
+
return kvm_set_memslot(kvm, old, &new, change);
}
EXPORT_SYMBOL_GPL(__kvm_set_memory_region);
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