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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6688C4332F for ; Thu, 6 Oct 2022 08:56:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231261AbiJFI4N (ORCPT ); Thu, 6 Oct 2022 04:56:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60720 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231244AbiJFI4M (ORCPT ); Thu, 6 Oct 2022 04:56:12 -0400 Received: from mail-lf1-x136.google.com (mail-lf1-x136.google.com [IPv6:2a00:1450:4864:20::136]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AE3A197D52 for ; Thu, 6 Oct 2022 01:56:09 -0700 (PDT) Received: by mail-lf1-x136.google.com with SMTP id s20so1688341lfi.11 for ; Thu, 06 Oct 2022 01:56:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date; bh=8RWQt9ojmR/E6rIyncCNc1lkldnlcrhWpGJj6b8ZrYc=; b=CT6RezdGJy/c1bZ4bgfPFQfXqCiDu0v/WOsA307v8CFvFhgi19voYrWIWcsxOIPnhf vwveJYqsSqB06IoqvGtY8YudsLZamRzjo0TV3seGFnKkUWQwgYtsT2H3AMFdqYRlYnZw JKyz2b7Rq6PGw+1vT9xW+mW/fvS93l4+JyApHzipdasVIQOsfHisPBGOpvg1Sv3FPvHE hIyDCkvvuf9TAGDTx78+y8cLJ9H3X9rmEwuugBMzeD2q0WsEZQkaS0I1evYwVfSYo1Z8 jdcOboANrbo6N9LEUHor3pEDD28xFPI5OZHMxznJ3gIo0VfMkfaPutpCR2QHwHAWpqew iFXg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date; bh=8RWQt9ojmR/E6rIyncCNc1lkldnlcrhWpGJj6b8ZrYc=; b=jTwmL/48fqn+TvXwiMW0Hb9Ywel9YoNfNsTIr/J0e1fb5Y/M/rXQdqgWKt4/7xphE3 kkBF9n79FkFpA4GuOR5memNSSMiODtOJLdPIq8bkc8eWbhzo8+4rWInD0k6Gx1n73l6m iLap+2+MOvZHL2ARD6r9lrSxct/0/xM4wsNDJERWr3Mt5ZFEV2+C9bRFz9okoMsPeMhx oaaWlXEd3q44tBbcyxLPWX3l6kCzgws9nE4yHK8ACG4kRG/zHh98WrxQVdRdUbHVqKcQ rH5AIRm/MnztwcHmvU0ftFuR1RmgOKKr6P3Ckab9b1y1GDZG7b41B0uO4IGYyl139+oq UiCw== X-Gm-Message-State: ACrzQf1uq+HsJvzSiCXPLgaydgxac2E8YBZN1VHDFndAadYLNu67SS6L R3fHirwddanZlc5zlLjhPlLW9fkZ202LTtnEPTnqLQ== X-Google-Smtp-Source: AMsMyM4bXmvIdym2WfRsWMI/tnfkvrSWBJtmv0RTGXMOpDJoCTIS+z2+pspjnZVrMWsgpd4rCXyB56J9s0gj2AriU7w= X-Received: by 2002:a05:6512:32c7:b0:4a2:4544:120d with SMTP id f7-20020a05651232c700b004a24544120dmr1589446lfg.598.1665046567768; Thu, 06 Oct 2022 01:56:07 -0700 (PDT) MIME-Version: 1.0 References: <20220915142913.2213336-1-chao.p.peng@linux.intel.com> <20220915142913.2213336-9-chao.p.peng@linux.intel.com> In-Reply-To: <20220915142913.2213336-9-chao.p.peng@linux.intel.com> From: Fuad Tabba Date: Thu, 6 Oct 2022 09:55:31 +0100 Message-ID: Subject: Re: [PATCH v8 8/8] KVM: Enable and expose KVM_MEM_PRIVATE To: Chao Peng Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-doc@vger.kernel.org, qemu-devel@nongnu.org, Paolo Bonzini , Jonathan Corbet , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , Hugh Dickins , Jeff Layton , "J . Bruce Fields" , Andrew Morton , Shuah Khan , Mike Rapoport , Steven Price , "Maciej S . Szmigiero" , Vlastimil Babka , Vishal Annapurve , Yu Zhang , "Kirill A . Shutemov" , luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com, david@redhat.com, aarcange@redhat.com, ddutile@redhat.com, dhildenb@redhat.com, Quentin Perret , Michael Roth , mhocko@suse.com, Muchun Song , wei.w.wang@intel.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org Hi, On Thu, Sep 15, 2022 at 3:37 PM Chao Peng wrote: > > Expose KVM_MEM_PRIVATE and memslot fields private_fd/offset to > userspace. KVM will register/unregister private memslot to fd-based > memory backing store and response to invalidation event from > inaccessible_notifier to zap the existing memory mappings in the > secondary page table. > > Whether KVM_MEM_PRIVATE is actually exposed to userspace is determined > by architecture code which can turn on it by overriding the default > kvm_arch_has_private_mem(). > > A 'kvm' reference is added in memslot structure since in > inaccessible_notifier callback we can only obtain a memslot reference > but 'kvm' is needed to do the zapping. > > Co-developed-by: Yu Zhang > Signed-off-by: Yu Zhang > Signed-off-by: Chao Peng > --- > include/linux/kvm_host.h | 1 + > virt/kvm/kvm_main.c | 116 +++++++++++++++++++++++++++++++++++++-- > 2 files changed, 111 insertions(+), 6 deletions(-) > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index b9906cdf468b..cb4eefac709c 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -589,6 +589,7 @@ struct kvm_memory_slot { > struct file *private_file; > loff_t private_offset; > struct inaccessible_notifier notifier; > + struct kvm *kvm; > }; > > static inline bool kvm_slot_can_be_private(const struct kvm_memory_slot *slot) > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 97d893f7482c..87e239d35b96 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -983,6 +983,57 @@ static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size, > xa_erase(&kvm->mem_attr_array, index); > return r; > } > + > +static void kvm_private_notifier_invalidate(struct inaccessible_notifier *notifier, > + pgoff_t start, pgoff_t end) > +{ > + struct kvm_memory_slot *slot = container_of(notifier, > + struct kvm_memory_slot, > + notifier); > + unsigned long base_pgoff = slot->private_offset >> PAGE_SHIFT; > + gfn_t start_gfn = slot->base_gfn; > + gfn_t end_gfn = slot->base_gfn + slot->npages; > + > + > + if (start > base_pgoff) > + start_gfn = slot->base_gfn + start - base_pgoff; > + > + if (end < base_pgoff + slot->npages) > + end_gfn = slot->base_gfn + end - base_pgoff; > + > + if (start_gfn >= end_gfn) > + return; > + > + kvm_zap_gfn_range(slot->kvm, start_gfn, end_gfn); > +} > + > +static struct inaccessible_notifier_ops kvm_private_notifier_ops = { > + .invalidate = kvm_private_notifier_invalidate, > +}; > + > +static inline void kvm_private_mem_register(struct kvm_memory_slot *slot) > +{ > + slot->notifier.ops = &kvm_private_notifier_ops; > + inaccessible_register_notifier(slot->private_file, &slot->notifier); > +} > + > +static inline void kvm_private_mem_unregister(struct kvm_memory_slot *slot) > +{ > + inaccessible_unregister_notifier(slot->private_file, &slot->notifier); > +} > + > +#else /* !CONFIG_HAVE_KVM_PRIVATE_MEM */ > + > +static inline void kvm_private_mem_register(struct kvm_memory_slot *slot) > +{ > + WARN_ON_ONCE(1); > +} > + > +static inline void kvm_private_mem_unregister(struct kvm_memory_slot *slot) > +{ > + WARN_ON_ONCE(1); > +} > + > #endif /* CONFIG_HAVE_KVM_PRIVATE_MEM */ > > #ifdef CONFIG_HAVE_KVM_PM_NOTIFIER > @@ -1029,6 +1080,11 @@ static void kvm_destroy_dirty_bitmap(struct kvm_memory_slot *memslot) > /* This does not remove the slot from struct kvm_memslots data structures */ > static void kvm_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot) > { > + if (slot->flags & KVM_MEM_PRIVATE) { > + kvm_private_mem_unregister(slot); > + fput(slot->private_file); > + } > + > kvm_destroy_dirty_bitmap(slot); > > kvm_arch_free_memslot(kvm, slot); > @@ -1600,10 +1656,16 @@ bool __weak kvm_arch_has_private_mem(struct kvm *kvm) > return false; > } > > -static int check_memory_region_flags(const struct kvm_user_mem_region *mem) > +static int check_memory_region_flags(struct kvm *kvm, > + const struct kvm_user_mem_region *mem) > { > u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES; > > +#ifdef CONFIG_HAVE_KVM_PRIVATE_MEM > + if (kvm_arch_has_private_mem(kvm)) > + valid_flags |= KVM_MEM_PRIVATE; > +#endif > + > #ifdef __KVM_HAVE_READONLY_MEM > valid_flags |= KVM_MEM_READONLY; > #endif > @@ -1679,6 +1741,9 @@ static int kvm_prepare_memory_region(struct kvm *kvm, > { > int r; > > + if (change == KVM_MR_CREATE && new->flags & KVM_MEM_PRIVATE) > + kvm_private_mem_register(new); > + >From the discussion I had with Kirill in the first patch *, should this check that the private_fd is inaccessible? [*] https://lore.kernel.org/all/20221003110129.bbee7kawhw5ed745@box.shutemov.name/ Cheers, /fuad > /* > * If dirty logging is disabled, nullify the bitmap; the old bitmap > * will be freed on "commit". If logging is enabled in both old and > @@ -1707,6 +1772,9 @@ static int kvm_prepare_memory_region(struct kvm *kvm, > if (r && new && new->dirty_bitmap && (!old || !old->dirty_bitmap)) > kvm_destroy_dirty_bitmap(new); > > + if (r && change == KVM_MR_CREATE && new->flags & KVM_MEM_PRIVATE) > + kvm_private_mem_unregister(new); > + > return r; > } > > @@ -2004,7 +2072,7 @@ int __kvm_set_memory_region(struct kvm *kvm, > int as_id, id; > int r; > > - r = check_memory_region_flags(mem); > + r = check_memory_region_flags(kvm, mem); > if (r) > return r; > > @@ -2023,6 +2091,10 @@ int __kvm_set_memory_region(struct kvm *kvm, > !access_ok((void __user *)(unsigned long)mem->userspace_addr, > mem->memory_size)) > return -EINVAL; > + if (mem->flags & KVM_MEM_PRIVATE && > + (mem->private_offset & (PAGE_SIZE - 1) || > + mem->private_offset > U64_MAX - mem->memory_size)) > + return -EINVAL; > if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_MEM_SLOTS_NUM) > return -EINVAL; > if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr) > @@ -2061,6 +2133,9 @@ int __kvm_set_memory_region(struct kvm *kvm, > if ((kvm->nr_memslot_pages + npages) < kvm->nr_memslot_pages) > return -EINVAL; > } else { /* Modify an existing slot. */ > + /* Private memslots are immutable, they can only be deleted. */ > + if (mem->flags & KVM_MEM_PRIVATE) > + return -EINVAL; > if ((mem->userspace_addr != old->userspace_addr) || > (npages != old->npages) || > ((mem->flags ^ old->flags) & KVM_MEM_READONLY)) > @@ -2089,10 +2164,27 @@ int __kvm_set_memory_region(struct kvm *kvm, > new->npages = npages; > new->flags = mem->flags; > new->userspace_addr = mem->userspace_addr; > + if (mem->flags & KVM_MEM_PRIVATE) { > + new->private_file = fget(mem->private_fd); > + if (!new->private_file) { > + r = -EINVAL; > + goto out; > + } > + new->private_offset = mem->private_offset; > + } > + > + new->kvm = kvm; > > r = kvm_set_memslot(kvm, old, new, change); > if (r) > - kfree(new); > + goto out; > + > + return 0; > + > +out: > + if (new->private_file) > + fput(new->private_file); > + kfree(new); > return r; > } > EXPORT_SYMBOL_GPL(__kvm_set_memory_region); > @@ -4747,16 +4839,28 @@ static long kvm_vm_ioctl(struct file *filp, > } > case KVM_SET_USER_MEMORY_REGION: { > struct kvm_user_mem_region mem; > - unsigned long size = sizeof(struct kvm_userspace_memory_region); > + unsigned int flags_offset = offsetof(typeof(mem), flags); > + unsigned long size; > + u32 flags; > > kvm_sanity_check_user_mem_region_alias(); > > + memset(&mem, 0, sizeof(mem)); > + > r = -EFAULT; > - if (copy_from_user(&mem, argp, size); > + if (get_user(flags, (u32 __user *)(argp + flags_offset))) > + goto out; > + > + if (flags & KVM_MEM_PRIVATE) > + size = sizeof(struct kvm_userspace_memory_region_ext); > + else > + size = sizeof(struct kvm_userspace_memory_region); > + > + if (copy_from_user(&mem, argp, size)) > goto out; > > r = -EINVAL; > - if (mem.flags & KVM_MEM_PRIVATE) > + if ((flags ^ mem.flags) & KVM_MEM_PRIVATE) > goto out; > > r = kvm_vm_ioctl_set_memory_region(kvm, &mem); > -- > 2.25.1 >