Messages in this thread | | | Date | Tue, 13 Sep 2011 13:50:49 +0300 | From | Avi Kivity <> | Subject | Re: [PATCH v3 01/11] KVM: MMU: avoid pte_list_desc running out in kvm_mmu_pte_write |
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On 09/13/2011 01:24 PM, Xiao Guangrong wrote: > On 09/13/2011 05:51 PM, Avi Kivity wrote: > > On 08/30/2011 05:34 AM, 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 > >> > >> @@ -3716,10 +3735,6 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u32 error_code, > >> goto out; > >> } > >> > >> - r = mmu_topup_memory_caches(vcpu); > >> - if (r) > >> - goto out; > >> - > >> er = x86_emulate_instruction(vcpu, cr2, 0, insn, insn_len); > >> > > > > Suppose we are out of memory, can't this get us in an endless loop? > > > > return -ENOMEM breaks as out (and kills the guest, likely). > > > > If memory is not enough, we just clear sptes on pte_write path(not prefetch spte), > the later page fault path can return -1 to let guest crash. Hmm? >
Yes.
btw, is rmap_can_add() sufficent? We allocate more than just rmaps in mmu_topup_memory_caches(). I guess it is, but this is getting tricky.
-- error compiling committee.c: too many arguments to function
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