> -----Original Message----- > From: kvm-owner@xxxxxxxxxxxxxxx [mailto:kvm-owner@xxxxxxxxxxxxxxx] On Behalf Of > Paul Mackerras > Sent: Tuesday, August 06, 2013 9:58 AM > To: Alexander Graf; Benjamin Herrenschmidt > Cc: kvm-ppc@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx > Subject: [PATCH 21/23] KVM: PPC: Book3S PR: Use mmu_notifier_retry() in > kvmppc_mmu_map_page() > > When the MM code is invalidating a range of pages, it calls the KVM > kvm_mmu_notifier_invalidate_range_start() notifier function, which calls > kvm_unmap_hva_range(), which arranges to flush all the existing host > HPTEs for guest pages. However, the Linux PTEs for the range being > flushed are still valid at that point. We are not supposed to establish > any new references to pages in the range until the ...range_end() > notifier gets called. The PPC-specific KVM code doesn't get any > explicit notification of that; instead, we are supposed to use > mmu_notifier_retry() to test whether we are or have been inside a > range flush notifier pair while we have been getting a page and > instantiating a host HPTE for the page. > > This therefore adds a call to mmu_notifier_retry inside > kvmppc_mmu_map_page(). This call is inside a region locked with > kvm->mmu_lock, which is the same lock that is called by the KVM > MMU notifier functions, thus ensuring that no new notification can > proceed while we are in the locked region. Inside this region we > also create the host HPTE and link the corresponding hpte_cache > structure into the lists used to find it later. We cannot allocate > the hpte_cache structure inside this locked region because that can > lead to deadlock, so we allocate it outside the region and free it > if we end up not using it. > > This also moves the updates of vcpu3s->hpte_cache_count inside the > regions locked with vcpu3s->mmu_lock, and does the increment in > kvmppc_mmu_hpte_cache_map() when the pte is added to the cache > rather than when it is allocated, in order that the hpte_cache_count > is accurate. > > Signed-off-by: Paul Mackerras <paulus@xxxxxxxxx> > --- > arch/powerpc/include/asm/kvm_book3s.h | 1 + > arch/powerpc/kvm/book3s_64_mmu_host.c | 37 ++++++++++++++++++++++++++--------- > arch/powerpc/kvm/book3s_mmu_hpte.c | 14 +++++++++---- > 3 files changed, 39 insertions(+), 13 deletions(-) > > diff --git a/arch/powerpc/include/asm/kvm_book3s.h > b/arch/powerpc/include/asm/kvm_book3s.h > index 4fe6864..e711e77 100644 > --- a/arch/powerpc/include/asm/kvm_book3s.h > +++ b/arch/powerpc/include/asm/kvm_book3s.h > @@ -143,6 +143,7 @@ extern long kvmppc_hv_find_lock_hpte(struct kvm *kvm, gva_t > eaddr, > > extern void kvmppc_mmu_hpte_cache_map(struct kvm_vcpu *vcpu, struct hpte_cache > *pte); > extern struct hpte_cache *kvmppc_mmu_hpte_cache_next(struct kvm_vcpu *vcpu); > +extern void kvmppc_mmu_hpte_cache_free(struct hpte_cache *pte); > extern void kvmppc_mmu_hpte_destroy(struct kvm_vcpu *vcpu); > extern int kvmppc_mmu_hpte_init(struct kvm_vcpu *vcpu); > extern void kvmppc_mmu_invalidate_pte(struct kvm_vcpu *vcpu, struct hpte_cache > *pte); > diff --git a/arch/powerpc/kvm/book3s_64_mmu_host.c > b/arch/powerpc/kvm/book3s_64_mmu_host.c > index 7fcf38f..b7e9504 100644 > --- a/arch/powerpc/kvm/book3s_64_mmu_host.c > +++ b/arch/powerpc/kvm/book3s_64_mmu_host.c > @@ -93,6 +93,13 @@ int kvmppc_mmu_map_page(struct kvm_vcpu *vcpu, struct > kvmppc_pte *orig_pte, > int r = 0; > int hpsize = MMU_PAGE_4K; > bool writable; > + unsigned long mmu_seq; > + struct kvm *kvm = vcpu->kvm; > + struct hpte_cache *cpte; > + > + /* used to check for invalidations in progress */ > + mmu_seq = kvm->mmu_notifier_seq; > + smp_rmb(); > > /* Get host physical address for gpa */ > hpaddr = kvmppc_gfn_to_pfn(vcpu, orig_pte->raddr >> PAGE_SHIFT, > @@ -143,6 +150,14 @@ int kvmppc_mmu_map_page(struct kvm_vcpu *vcpu, struct > kvmppc_pte *orig_pte, > > hash = hpt_hash(vpn, mmu_psize_defs[hpsize].shift, MMU_SEGSIZE_256M); > > + cpte = kvmppc_mmu_hpte_cache_next(vcpu); > + > + spin_lock(&kvm->mmu_lock); > + if (!cpte || mmu_notifier_retry(kvm, mmu_seq)) { > + r = -EAGAIN; Pauls, I am trying to understand the flow; does retry mean that we do not create the mapping and return to guest, which will fault again and then we will retry? Thanks -Bharat > + goto out_unlock; > + } > + > map_again: > hpteg = ((hash & htab_hash_mask) * HPTES_PER_GROUP); > > @@ -150,7 +165,7 @@ map_again: > if (attempt > 1) > if (ppc_md.hpte_remove(hpteg) < 0) { > r = -1; > - goto out; > + goto out_unlock; > } > > ret = ppc_md.hpte_insert(hpteg, vpn, hpaddr, rflags, vflags, > @@ -163,8 +178,6 @@ map_again: > attempt++; > goto map_again; > } else { > - struct hpte_cache *pte = kvmppc_mmu_hpte_cache_next(vcpu); > - > trace_kvm_book3s_64_mmu_map(rflags, hpteg, > vpn, hpaddr, orig_pte); > > @@ -175,15 +188,21 @@ map_again: > hpteg = ((hash & htab_hash_mask) * HPTES_PER_GROUP); > } > > - pte->slot = hpteg + (ret & 7); > - pte->host_vpn = vpn; > - pte->pte = *orig_pte; > - pte->pfn = hpaddr >> PAGE_SHIFT; > - pte->pagesize = hpsize; > + cpte->slot = hpteg + (ret & 7); > + cpte->host_vpn = vpn; > + cpte->pte = *orig_pte; > + cpte->pfn = hpaddr >> PAGE_SHIFT; > + cpte->pagesize = hpsize; > > - kvmppc_mmu_hpte_cache_map(vcpu, pte); > + kvmppc_mmu_hpte_cache_map(vcpu, cpte); > + cpte = NULL; > } > + > +out_unlock: > + spin_unlock(&kvm->mmu_lock); > kvm_release_pfn_clean(hpaddr >> PAGE_SHIFT); > + if (cpte) > + kvmppc_mmu_hpte_cache_free(cpte); > > out: > return r; > diff --git a/arch/powerpc/kvm/book3s_mmu_hpte.c > b/arch/powerpc/kvm/book3s_mmu_hpte.c > index d2d280b..6b79bfc 100644 > --- a/arch/powerpc/kvm/book3s_mmu_hpte.c > +++ b/arch/powerpc/kvm/book3s_mmu_hpte.c > @@ -98,6 +98,8 @@ void kvmppc_mmu_hpte_cache_map(struct kvm_vcpu *vcpu, struct > hpte_cache *pte) > &vcpu3s->hpte_hash_vpte_64k[index]); > #endif > > + vcpu3s->hpte_cache_count++; > + > spin_unlock(&vcpu3s->mmu_lock); > } > > @@ -131,10 +133,10 @@ static void invalidate_pte(struct kvm_vcpu *vcpu, struct > hpte_cache *pte) > #ifdef CONFIG_PPC_BOOK3S_64 > hlist_del_init_rcu(&pte->list_vpte_64k); > #endif > + vcpu3s->hpte_cache_count--; > > spin_unlock(&vcpu3s->mmu_lock); > > - vcpu3s->hpte_cache_count--; > call_rcu(&pte->rcu_head, free_pte_rcu); > } > > @@ -331,15 +333,19 @@ struct hpte_cache *kvmppc_mmu_hpte_cache_next(struct > kvm_vcpu *vcpu) > struct kvmppc_vcpu_book3s *vcpu3s = to_book3s(vcpu); > struct hpte_cache *pte; > > - pte = kmem_cache_zalloc(hpte_cache, GFP_KERNEL); > - vcpu3s->hpte_cache_count++; > - > if (vcpu3s->hpte_cache_count == HPTEG_CACHE_NUM) > kvmppc_mmu_pte_flush_all(vcpu); > > + pte = kmem_cache_zalloc(hpte_cache, GFP_KERNEL); > + > return pte; > } > > +void kvmppc_mmu_hpte_cache_free(struct hpte_cache *pte) > +{ > + kmem_cache_free(hpte_cache, pte); > +} > + > void kvmppc_mmu_hpte_destroy(struct kvm_vcpu *vcpu) > { > kvmppc_mmu_pte_flush(vcpu, 0, 0); > -- > 1.8.3.1 > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
