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Message-Id: <20121220233545.95378d066b2ce61a76106a88@gmail.com> Date: Thu, 20 Dec 2012 23:35:45 +0900 From: Takuya Yoshikawa <takuya.yoshikawa@...il.com> To: Alex Williamson <alex.williamson@...hat.com> Cc: Gleb Natapov <gleb@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>, Takuya Yoshikawa <yoshikawa_takuya_b1@....ntt.co.jp>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 0/7] KVM: Alleviate mmu_lock hold time when we start dirty logging On Thu, 20 Dec 2012 06:41:27 -0700 Alex Williamson <alex.williamson@...hat.com> wrote: > Hmm, isn't the fix as simple as: > > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -847,7 +847,8 @@ int __kvm_set_memory_region(struct kvm *kvm, > GFP_KERNEL); > if (!slots) > goto out_free; > - } > + } else > + slots->generation = kvm->memslots->generation; > > /* map new memory slot into the iommu */ > if (npages) { > > Or even just slots->generation++ since we're holding the lock across all > of this. Yes, the fix should work, but I do not want to update the generation from outside of update_memslots(). > The original patch can be reverted, there are no following dependencies, > but the idea was that we're making the memslot array larger, so there > could be more pressure in allocating it, so let's not trivially do extra > frees and allocs. Thanks, I agree that the current set_memory_region() is not good for frequent updates. But the alloc/free is not a major factor at the moment: flushing shadows should be more problematic. Thanks, Takuya -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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