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KVM: MMU: limit rmap chain length
Otherwise the host can spend too long traversing an rmap chain, which happens under a spinlock. Cc: stable@kernel.org Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com>
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parent
e9cbde8c15
commit
53a27b39ff
1 changed files with 28 additions and 5 deletions
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@ -489,16 +489,20 @@ static unsigned long *gfn_to_rmap(struct kvm *kvm, gfn_t gfn, int lpage)
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*
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* If rmapp bit zero is one, (then rmap & ~1) points to a struct kvm_rmap_desc
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* containing more mappings.
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*
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* Returns the number of rmap entries before the spte was added or zero if
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* the spte was not added.
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*
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*/
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static void rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn, int lpage)
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static int rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn, int lpage)
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{
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struct kvm_mmu_page *sp;
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struct kvm_rmap_desc *desc;
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unsigned long *rmapp;
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int i;
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int i, count = 0;
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if (!is_rmap_pte(*spte))
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return;
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return count;
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gfn = unalias_gfn(vcpu->kvm, gfn);
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sp = page_header(__pa(spte));
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sp->gfns[spte - sp->spt] = gfn;
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@ -515,8 +519,10 @@ static void rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn, int lpage)
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} else {
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rmap_printk("rmap_add: %p %llx many->many\n", spte, *spte);
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desc = (struct kvm_rmap_desc *)(*rmapp & ~1ul);
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while (desc->shadow_ptes[RMAP_EXT-1] && desc->more)
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while (desc->shadow_ptes[RMAP_EXT-1] && desc->more) {
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desc = desc->more;
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count += RMAP_EXT;
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}
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if (desc->shadow_ptes[RMAP_EXT-1]) {
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desc->more = mmu_alloc_rmap_desc(vcpu);
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desc = desc->more;
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@ -525,6 +531,7 @@ static void rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn, int lpage)
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;
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desc->shadow_ptes[i] = spte;
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}
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return count;
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}
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static void rmap_desc_remove_entry(unsigned long *rmapp,
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@ -754,6 +761,19 @@ static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp)
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return young;
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}
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#define RMAP_RECYCLE_THRESHOLD 1000
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static void rmap_recycle(struct kvm_vcpu *vcpu, gfn_t gfn, int lpage)
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{
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unsigned long *rmapp;
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gfn = unalias_gfn(vcpu->kvm, gfn);
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rmapp = gfn_to_rmap(vcpu->kvm, gfn, lpage);
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kvm_unmap_rmapp(vcpu->kvm, rmapp);
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kvm_flush_remote_tlbs(vcpu->kvm);
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}
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int kvm_age_hva(struct kvm *kvm, unsigned long hva)
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{
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return kvm_handle_hva(kvm, hva, kvm_age_rmapp);
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@ -1741,6 +1761,7 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *shadow_pte,
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{
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int was_rmapped = 0;
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int was_writeble = is_writeble_pte(*shadow_pte);
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int rmap_count;
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pgprintk("%s: spte %llx access %x write_fault %d"
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" user_fault %d gfn %lx\n",
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@ -1782,9 +1803,11 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *shadow_pte,
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page_header_update_slot(vcpu->kvm, shadow_pte, gfn);
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if (!was_rmapped) {
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rmap_add(vcpu, shadow_pte, gfn, largepage);
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rmap_count = rmap_add(vcpu, shadow_pte, gfn, largepage);
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if (!is_rmap_pte(*shadow_pte))
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kvm_release_pfn_clean(pfn);
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if (rmap_count > RMAP_RECYCLE_THRESHOLD)
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rmap_recycle(vcpu, gfn, largepage);
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} else {
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if (was_writeble)
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kvm_release_pfn_dirty(pfn);
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