From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D9FDCC352A3 for ; Thu, 6 Feb 2020 22:12:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A4757217BA for ; Thu, 6 Feb 2020 22:12:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="E4ZDUGpm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727527AbgBFWMW (ORCPT ); Thu, 6 Feb 2020 17:12:22 -0500 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:39287 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727505AbgBFWMW (ORCPT ); Thu, 6 Feb 2020 17:12:22 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1581027141; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=xnxqE/nCX2EzFDbA9kwFrPUv5TZytfq4VJeA0RRzpMU=; b=E4ZDUGpmp2oHoTMhETV2mrexFeQo6QizBUAS1AngJSea8F8fHZNwkElTcLVOG4QxURnA46 4tzRZSHrgfhX0cm7C3LMj6ZAhYB/9/Y3jPqbyZjC+8GTMIyWFbSDU2oSiFuoGwJv6uWDbu 4JlbyfRqwW21aWWNVr6YvRzUmlyEITg= Received: from mail-qk1-f197.google.com (mail-qk1-f197.google.com [209.85.222.197]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-113-Iv81YtAfNAmCVz5rzUR1XQ-1; Thu, 06 Feb 2020 17:12:15 -0500 X-MC-Unique: Iv81YtAfNAmCVz5rzUR1XQ-1 Received: by mail-qk1-f197.google.com with SMTP id y6so5405qki.13 for ; Thu, 06 Feb 2020 14:12:15 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=xnxqE/nCX2EzFDbA9kwFrPUv5TZytfq4VJeA0RRzpMU=; b=dd+bs5HXoOxDbKQmTLU4mOoxdjelx9fhA8ZnBr8SX0En3QUee3sRffSJkZSdC2vRRK MVjy4JKcezKps4gse7pCzaGJxhcdfzXW8BduWYsR2YG3pFTfcMZCY85JHZrDv8kgSUBe ac4XpYF4TTXiWZFPN/vnFh5N9cg8Xf6hPpNZAmyFyJh/WV4zHSJ8UaIpM3c7Qb9Ies9R NrI2OHVY4Q7G55407dJi9qWm0RIo/mTrRMXEdAZeidclPVQ0VIMjypq/UAVvqB9jeQAq yH9znR6f9CVDJfSSIL3w08WpRMjcqxcg/j+wqzTNh4TedEnK289WZrmfOh3O/tEaDXb8 eOgw== X-Gm-Message-State: APjAAAXcSOr2rKeIzTvzLfO1jt8Q4kMbUpEo9tRAOL2HCQrJNZ+Sex/+ MpZKEIILjpXAU8G3RzSB9kB1BfQplBfoFydIAlp/TKSqMEA5Dn1O/cTuYugA0N3g7mf9Ok3qQIX OjxE+B/Du8HMS X-Received: by 2002:ac8:1c1d:: with SMTP id a29mr4676765qtk.183.1581027135107; Thu, 06 Feb 2020 14:12:15 -0800 (PST) X-Google-Smtp-Source: APXvYqw/2cyK6F4lh5rp4dz7WvwTupqk8fbtvVzQEcyTi4bd7WqahSqSpQi7XlP32hR4RTgKgW30Yg== X-Received: by 2002:ac8:1c1d:: with SMTP id a29mr4676750qtk.183.1581027134836; Thu, 06 Feb 2020 14:12:14 -0800 (PST) Received: from xz-x1 ([2607:9880:19c8:32::2]) by smtp.gmail.com with ESMTPSA id w1sm357608qtk.31.2020.02.06.14.12.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Feb 2020 14:12:14 -0800 (PST) Date: Thu, 6 Feb 2020 17:12:08 -0500 From: Peter Xu To: Sean Christopherson Cc: Paolo Bonzini , Paul Mackerras , Christian Borntraeger , Janosch Frank , David Hildenbrand , Cornelia Huck , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Marc Zyngier , James Morse , Julien Thierry , Suzuki K Poulose , linux-mips@vger.kernel.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, Christoffer Dall , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Subject: Re: [PATCH v5 18/19] KVM: Dynamically size memslot array based on number of used slots Message-ID: <20200206221208.GI700495@xz-x1> References: <20200121223157.15263-1-sean.j.christopherson@intel.com> <20200121223157.15263-19-sean.j.christopherson@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200121223157.15263-19-sean.j.christopherson@intel.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Jan 21, 2020 at 02:31:56PM -0800, Sean Christopherson wrote: > Now that the memslot logic doesn't assume memslots are always non-NULL, > dynamically size the array of memslots instead of unconditionally > allocating memory for the maximum number of memslots. > > Note, because a to-be-deleted memslot must first be invalidated, the > array size cannot be immediately reduced when deleting a memslot. > However, consecutive deletions will realize the memory savings, i.e. > a second deletion will trim the entry. > > Tested-by: Christoffer Dall > Tested-by: Marc Zyngier > Signed-off-by: Sean Christopherson > --- > include/linux/kvm_host.h | 2 +- > virt/kvm/kvm_main.c | 31 ++++++++++++++++++++++++++++--- > 2 files changed, 29 insertions(+), 4 deletions(-) > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 60ddfdb69378..8bb6fb127387 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -431,11 +431,11 @@ static inline int kvm_arch_vcpu_memslots_id(struct kvm_vcpu *vcpu) > */ > struct kvm_memslots { > u64 generation; > - struct kvm_memory_slot memslots[KVM_MEM_SLOTS_NUM]; > /* The mapping table from slot id to the index in memslots[]. */ > short id_to_index[KVM_MEM_SLOTS_NUM]; > atomic_t lru_slot; > int used_slots; > + struct kvm_memory_slot memslots[]; This patch is tested so I believe this works, however normally I need to do similar thing with [0] otherwise gcc might complaint. Is there any trick behind to make this work? Or is that because of different gcc versions? > }; > > struct kvm { > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 9b614cf2ca20..ed392ce64e59 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -565,7 +565,7 @@ static struct kvm_memslots *kvm_alloc_memslots(void) > return NULL; > > for (i = 0; i < KVM_MEM_SLOTS_NUM; i++) > - slots->id_to_index[i] = slots->memslots[i].id = -1; > + slots->id_to_index[i] = -1; > > return slots; > } > @@ -1077,6 +1077,32 @@ static struct kvm_memslots *install_new_memslots(struct kvm *kvm, > return old_memslots; > } > > +/* > + * Note, at a minimum, the current number of used slots must be allocated, even > + * when deleting a memslot, as we need a complete duplicate of the memslots for > + * use when invalidating a memslot prior to deleting/moving the memslot. > + */ > +static struct kvm_memslots *kvm_dup_memslots(struct kvm_memslots *old, > + enum kvm_mr_change change) > +{ > + struct kvm_memslots *slots; > + size_t old_size, new_size; > + > + old_size = sizeof(struct kvm_memslots) + > + (sizeof(struct kvm_memory_slot) * old->used_slots); > + > + if (change == KVM_MR_CREATE) > + new_size = old_size + sizeof(struct kvm_memory_slot); > + else > + new_size = old_size; > + > + slots = kvzalloc(new_size, GFP_KERNEL_ACCOUNT); > + if (likely(slots)) > + memcpy(slots, old, old_size); (Maybe directly copy into it?) > + > + return slots; > +} > + > static int kvm_set_memslot(struct kvm *kvm, > const struct kvm_userspace_memory_region *mem, > struct kvm_memory_slot *old, > @@ -1087,10 +1113,9 @@ static int kvm_set_memslot(struct kvm *kvm, > struct kvm_memslots *slots; > int r; > > - slots = kvzalloc(sizeof(struct kvm_memslots), GFP_KERNEL_ACCOUNT); > + slots = kvm_dup_memslots(__kvm_memslots(kvm, as_id), change); > if (!slots) > return -ENOMEM; > - memcpy(slots, __kvm_memslots(kvm, as_id), sizeof(struct kvm_memslots)); > > if (change == KVM_MR_DELETE || change == KVM_MR_MOVE) { > /* > -- > 2.24.1 > -- Peter Xu