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KVM: Optimize overlapping memslots check 

Do a quick lookup for possibly overlapping gfns when creating or moving
a memslot instead of performing a linear scan of the whole memslot set.

Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
[sean: tweaked params to avoid churn in future cleanup]
Reviewed-by: Sean Christopherson <seanjc@google.com>
Message-Id: <a4795e5c2f624754e9c0aab023ebda1966feb3e1.1638817641.git.maciej.szmigiero@oracle.com>
This commit is contained in:
Maciej S. Szmigiero 2021-12-06 20:54:33 +01:00 committed by Paolo Bonzini
parent f4209439b5
commit 44401a2047
1 changed files with 22 additions and 14 deletions
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36
virt/kvm/kvm_main.c
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@ -1815,6 +1815,19 @@ static int kvm_set_memslot(struct kvm *kvm,
return 0;
}
static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id,
gfn_t start, gfn_t end)
{
struct kvm_memslot_iter iter;
kvm_for_each_memslot_in_gfn_range(&iter, slots, start, end) {
if (iter.slot->id != id)
return true;
}
return false;
}
/*
* Allocate some memory and give it an address in the guest physical address
* space.
@ -1826,8 +1839,9 @@ static int kvm_set_memslot(struct kvm *kvm,
int __kvm_set_memory_region(struct kvm *kvm,
const struct kvm_userspace_memory_region *mem)
{
struct kvm_memory_slot *old, *tmp;
struct kvm_memory_slot *old;
struct kvm_memory_slot new;
struct kvm_memslots *slots;
enum kvm_mr_change change;
int as_id, id;
int r;
@ -1856,11 +1870,13 @@ int __kvm_set_memory_region(struct kvm *kvm,
if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
return -EINVAL;
slots = __kvm_memslots(kvm, as_id);
/*
* Note, the old memslot (and the pointer itself!) may be invalidated
* and/or destroyed by kvm_set_memslot().
*/
old = id_to_memslot(__kvm_memslots(kvm, as_id), id);
old = id_to_memslot(slots, id);
if (!mem->memory_size) {
if (!old || !old->npages)
@ -1909,18 +1925,10 @@ int __kvm_set_memory_region(struct kvm *kvm,
return 0;
}
if ((change == KVM_MR_CREATE) || (change == KVM_MR_MOVE)) {
int bkt;
/* Check for overlaps */
kvm_for_each_memslot(tmp, bkt, __kvm_memslots(kvm, as_id)) {
if (tmp->id == id)
continue;
if (!((new.base_gfn + new.npages <= tmp->base_gfn) ||
(new.base_gfn >= tmp->base_gfn + tmp->npages)))
return -EEXIST;
}
}
if ((change == KVM_MR_CREATE || change == KVM_MR_MOVE) &&
kvm_check_memslot_overlap(slots, id, new.base_gfn,
new.base_gfn + new.npages))
return -EEXIST;
return kvm_set_memslot(kvm, old, &new, change);
}