| Message ID | 1428990690-20119-2-git-send-email-wanpeng.li@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Apr 13, 2015 at 10:51 PM, Wanpeng Li <wanpeng.li@linux.intel.com> wrote: > As Andre pointed out: (Andres) > > | 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. > > Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com> Reviewed-by: Andres Lagar-Cavilla <andreslc@google.com> Thanks > --- > 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 >
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); }
As Andre 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. Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com> --- arch/x86/kvm/mmu.c | 12 ++---------- 1 file changed, 2 insertions(+), 10 deletions(-)