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[35.247.111.240]) by smtp.gmail.com with ESMTPSA id x13sm314784pjl.22.2021.05.19.14.24.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 May 2021 14:24:09 -0700 (PDT) Date: Wed, 19 May 2021 21:24:05 +0000 From: Sean Christopherson To: "Maciej S. Szmigiero" Cc: Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Igor Mammedov , Marc Zyngier , James Morse , Julien Thierry , Suzuki K Poulose , Huacai Chen , Aleksandar Markovic , Paul Mackerras , Christian Borntraeger , Janosch Frank , David Hildenbrand , Cornelia Huck , Claudio Imbrenda , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/8] KVM: Integrate gfn_to_memslot_approx() into search_memslots() Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Sun, May 16, 2021, Maciej S. Szmigiero wrote: > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 8895b95b6a22..3c40c7d32f7e 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -1091,10 +1091,14 @@ bool kvm_arch_irqfd_allowed(struct kvm *kvm, struct kvm_irqfd *args); > * gfn_to_memslot() itself isn't here as an inline because that would > * bloat other code too much. > * > + * With "approx" set returns the memslot also when the address falls > + * in a hole. In that case one of the memslots bordering the hole is > + * returned. > + * > * IMPORTANT: Slots are sorted from highest GFN to lowest GFN! > */ > static inline struct kvm_memory_slot * > -search_memslots(struct kvm_memslots *slots, gfn_t gfn) > +search_memslots(struct kvm_memslots *slots, gfn_t gfn, bool approx) An alternative to modifying the PPC code would be to make the existing search_memslots() a wrapper to __search_memslots(), with the latter taking @approx. We might also want to make this __always_inline to improve the likelihood of the compiler optimizing away @approx. I doubt it matters in practice... > { > int start = 0, end = slots->used_slots; > int slot = atomic_read(&slots->lru_slot); > @@ -1116,19 +1120,22 @@ search_memslots(struct kvm_memslots *slots, gfn_t gfn) > start = slot + 1; > } > > + if (approx && start >= slots->used_slots) > + return &memslots[slots->used_slots - 1]; > + > if (start < slots->used_slots && gfn >= memslots[start].base_gfn && > gfn < memslots[start].base_gfn + memslots[start].npages) { > atomic_set(&slots->lru_slot, start); > return &memslots[start]; > } > > - return NULL; > + return approx ? &memslots[start] : NULL; > } > > static inline struct kvm_memory_slot * > __gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn) > { > - return search_memslots(slots, gfn); > + return search_memslots(slots, gfn, false); > } > > static inline unsigned long