Messages in this thread | | | Date | Wed, 27 Jul 2011 12:00:28 +0300 | From | Avi Kivity <> | Subject | Re: [PATCH 01/11] KVM: MMU: avoid pte_list_desc run out in kvm_mmu_pte_write |
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On 07/26/2011 02:25 PM, Xiao Guangrong wrote: > kvm_mmu_pte_write is unsafe since we need to alloc pte_list_desc in the > function when spte is prefetched, unfortunately, we can not know how many > spte need to be prefetched on this path, that means we can use out of the > free pte_list_desc object in the cache, and BUG_ON() is triggered, also some > path does not fill the cache, such as INS instruction emulated that does not > trigger page fault > > > void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa, > const u8 *new, int bytes, > bool guest_initiated) > @@ -3583,6 +3596,7 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa, > break; > } > > + mmu_topup_memory_caches(vcpu);
Please add a comment here describing why it's okay to ignore the error return.
> spin_lock(&vcpu->kvm->mmu_lock); > if (atomic_read(&vcpu->kvm->arch.invlpg_counter) != invlpg_counter) > gentry = 0; > @@ -3653,7 +3667,7 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa, > mmu_page_zap_pte(vcpu->kvm, sp, spte); > if (gentry&& > !((sp->role.word ^ vcpu->arch.mmu.base_role.word) > - & mask.word)) > + & mask.word)&& get_free_pte_list_desc_nr(vcpu)) > mmu_pte_write_new_pte(vcpu, sp, spte,&gentry);
Wow, this bug was here since 2.6.23. Good catch.
Please wrap or rename get_free_pte_list_desc_nr() in rmap_can_add(vcpu) so it's clearer why we're doing this.
-- error compiling committee.c: too many arguments to function
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