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Subject[PATCH v2] kvm: mmu: don't do memslot overflow check
Date
As Andres pointed out:

| I don't understand the value of this check here. Are we looking for a
| broken memslot? Shouldn't this be a BUG_ON? Is this the place to care
| about these things? npages is capped to KVM_MEM_MAX_NR_PAGES, i.e.
| 2^31. A 64 bit overflow would be caused by a gigantic gfn_start which
| would be trouble in many other ways.

This patch drops the memslot overflow check to make the codes more simple.

Reviewed-by: Andres Lagar-Cavilla <andreslc@google.com>
Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
v1 -> v2:
* Fix Andres's name
* Add Andres's Reviewed-by

arch/x86/kvm/mmu.c | 12 ++----------
1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 2a0d77e..9265fda 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4505,19 +4505,12 @@ void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
bool flush = false;
unsigned long *rmapp;
unsigned long last_index, index;
- gfn_t gfn_start, gfn_end;

spin_lock(&kvm->mmu_lock);

- gfn_start = memslot->base_gfn;
- gfn_end = memslot->base_gfn + memslot->npages - 1;
-
- if (gfn_start >= gfn_end)
- goto out;
-
rmapp = memslot->arch.rmap[0];
- last_index = gfn_to_index(gfn_end, memslot->base_gfn,
- PT_PAGE_TABLE_LEVEL);
+ last_index = gfn_to_index(memslot->base_gfn + memslot->npages - 1,
+ memslot->base_gfn, PT_PAGE_TABLE_LEVEL);

for (index = 0; index <= last_index; ++index, ++rmapp) {
if (*rmapp)
@@ -4535,7 +4528,6 @@ void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
if (flush)
kvm_flush_remote_tlbs(kvm);

-out:
spin_unlock(&kvm->mmu_lock);
}

--
1.9.1


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