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 0EF76C6370A for ; Thu, 8 Dec 2022 11:18:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229678AbiLHLSW (ORCPT ); Thu, 8 Dec 2022 06:18:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49224 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229628AbiLHLST (ORCPT ); Thu, 8 Dec 2022 06:18:19 -0500 Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0BCD852179; Thu, 8 Dec 2022 03:18:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1670498291; x=1702034291; h=date:from:to:cc:subject:message-id:reply-to:references: mime-version:in-reply-to; bh=9X/XdL7eFz48zkUBVXUnL2TxJxurQ0v9FK2EcyHu93s=; b=JmxCA7uFzycf2czcSiT24HjMuZmfSj5xSdHQyTyOITAhYDIaPZyXQcXo D0m8Xy8Fhyp1UqFFMztNAh8DzbqYdJsOxKJ1C5+McoRfeuxGSjbzUtcXO aO8HlLsPCkdhCbuKph0pVK/QDq1KWKJuT4gmtbHGAK0N04o2wTrzWiL6Z OWKCLsOhr0AXT4Dag3e5m/gSNk+RpBGRXrkEMPJBkWrfjS32H7zjmIcY1 Be5Eb/5d0PR5KOQN/r+SbuWaokSymBTaT3xd217oF4lAtxcJ5+/mFbSUM 1YnxPgqfZA/9QQYhttgrg9e3ZaWUONEE9Y86W0rIGiO2TdA0C1JMqSrlQ g==; X-IronPort-AV: E=McAfee;i="6500,9779,10554"; a="314793004" X-IronPort-AV: E=Sophos;i="5.96,227,1665471600"; d="scan'208";a="314793004" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Dec 2022 03:18:07 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10554"; a="677717537" X-IronPort-AV: E=Sophos;i="5.96,227,1665471600"; d="scan'208";a="677717537" Received: from chaop.bj.intel.com (HELO localhost) ([10.240.193.75]) by orsmga008.jf.intel.com with ESMTP; 08 Dec 2022 03:17:55 -0800 Date: Thu, 8 Dec 2022 19:13:36 +0800 From: Chao Peng To: Fuad Tabba Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-arch@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 , Arnd Bergmann , Naoya Horiguchi , Miaohe Lin , 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, wei.w.wang@intel.com Subject: Re: [PATCH v10 6/9] KVM: Unmap existing mappings when change the memory attributes Message-ID: <20221208111336.GA1304936@chaop.bj.intel.com> Reply-To: Chao Peng References: <20221202061347.1070246-1-chao.p.peng@linux.intel.com> <20221202061347.1070246-7-chao.p.peng@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Wed, Dec 07, 2022 at 05:16:34PM +0000, Fuad Tabba wrote: > Hi, > > On Fri, Dec 2, 2022 at 6:19 AM Chao Peng wrote: > > > > Unmap the existing guest mappings when memory attribute is changed > > between shared and private. This is needed because shared pages and > > private pages are from different backends, unmapping existing ones > > gives a chance for page fault handler to re-populate the mappings > > according to the new attribute. > > > > Only architecture has private memory support needs this and the > > supported architecture is expected to rewrite the weak > > kvm_arch_has_private_mem(). > > This kind of ties into the discussion of being able to share memory in > place. For pKVM for example, shared and private memory would have the > same backend, and the unmapping wouldn't be needed. > > So I guess that, instead of kvm_arch_has_private_mem(), can the check > be done differently, e.g., with a different function, say > kvm_arch_private_notify_attribute_change() (but maybe with a more > friendly name than what I suggested :) )? Besides controlling the unmapping here, kvm_arch_has_private_mem() is also used to gate the memslot KVM_MEM_PRIVATE flag in patch09. I know unmapping is confirmed unnecessary for pKVM, but how about KVM_MEM_PRIVATE? Will pKVM add its own flag or reuse KVM_MEM_PRIVATE? If the answer is the latter, then yes we should use a different check which only works for confidential usages here. Thanks, Chao > > Thanks, > /fuad > > > > > Also, during memory attribute changing and the unmapping time frame, > > page fault handler may happen in the same memory range and can cause > > incorrect page state, invoke kvm_mmu_invalidate_* helpers to let the > > page fault handler retry during this time frame. > > > > Signed-off-by: Chao Peng > > --- > > include/linux/kvm_host.h | 7 +- > > virt/kvm/kvm_main.c | 168 ++++++++++++++++++++++++++------------- > > 2 files changed, 116 insertions(+), 59 deletions(-) > > > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index 3d69484d2704..3331c0c92838 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -255,7 +255,6 @@ bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, > > int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu); > > #endif > > > > -#ifdef KVM_ARCH_WANT_MMU_NOTIFIER > > struct kvm_gfn_range { > > struct kvm_memory_slot *slot; > > gfn_t start; > > @@ -264,6 +263,8 @@ struct kvm_gfn_range { > > bool may_block; > > }; > > bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range); > > + > > +#ifdef KVM_ARCH_WANT_MMU_NOTIFIER > > bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range); > > bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range); > > bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range); > > @@ -785,11 +786,12 @@ struct kvm { > > > > #if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER) > > struct mmu_notifier mmu_notifier; > > +#endif > > unsigned long mmu_invalidate_seq; > > long mmu_invalidate_in_progress; > > gfn_t mmu_invalidate_range_start; > > gfn_t mmu_invalidate_range_end; > > -#endif > > + > > struct list_head devices; > > u64 manual_dirty_log_protect; > > struct dentry *debugfs_dentry; > > @@ -1480,6 +1482,7 @@ bool kvm_arch_dy_has_pending_interrupt(struct kvm_vcpu *vcpu); > > int kvm_arch_post_init_vm(struct kvm *kvm); > > void kvm_arch_pre_destroy_vm(struct kvm *kvm); > > int kvm_arch_create_vm_debugfs(struct kvm *kvm); > > +bool kvm_arch_has_private_mem(struct kvm *kvm); > > > > #ifndef __KVM_HAVE_ARCH_VM_ALLOC > > /* > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > > index ad55dfbc75d7..4e1e1e113bf0 100644 > > --- a/virt/kvm/kvm_main.c > > +++ b/virt/kvm/kvm_main.c > > @@ -520,6 +520,62 @@ void kvm_destroy_vcpus(struct kvm *kvm) > > } > > EXPORT_SYMBOL_GPL(kvm_destroy_vcpus); > > > > +void kvm_mmu_invalidate_begin(struct kvm *kvm) > > +{ > > + /* > > + * The count increase must become visible at unlock time as no > > + * spte can be established without taking the mmu_lock and > > + * count is also read inside the mmu_lock critical section. > > + */ > > + kvm->mmu_invalidate_in_progress++; > > + > > + if (likely(kvm->mmu_invalidate_in_progress == 1)) { > > + kvm->mmu_invalidate_range_start = INVALID_GPA; > > + kvm->mmu_invalidate_range_end = INVALID_GPA; > > + } > > +} > > + > > +void kvm_mmu_invalidate_range_add(struct kvm *kvm, gfn_t start, gfn_t end) > > +{ > > + WARN_ON_ONCE(!kvm->mmu_invalidate_in_progress); > > + > > + if (likely(kvm->mmu_invalidate_in_progress == 1)) { > > + kvm->mmu_invalidate_range_start = start; > > + kvm->mmu_invalidate_range_end = end; > > + } else { > > + /* > > + * Fully tracking multiple concurrent ranges has diminishing > > + * returns. Keep things simple and just find the minimal range > > + * which includes the current and new ranges. As there won't be > > + * enough information to subtract a range after its invalidate > > + * completes, any ranges invalidated concurrently will > > + * accumulate and persist until all outstanding invalidates > > + * complete. > > + */ > > + kvm->mmu_invalidate_range_start = > > + min(kvm->mmu_invalidate_range_start, start); > > + kvm->mmu_invalidate_range_end = > > + max(kvm->mmu_invalidate_range_end, end); > > + } > > +} > > + > > +void kvm_mmu_invalidate_end(struct kvm *kvm) > > +{ > > + /* > > + * This sequence increase will notify the kvm page fault that > > + * the page that is going to be mapped in the spte could have > > + * been freed. > > + */ > > + kvm->mmu_invalidate_seq++; > > + smp_wmb(); > > + /* > > + * The above sequence increase must be visible before the > > + * below count decrease, which is ensured by the smp_wmb above > > + * in conjunction with the smp_rmb in mmu_invalidate_retry(). > > + */ > > + kvm->mmu_invalidate_in_progress--; > > +} > > + > > #if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER) > > static inline struct kvm *mmu_notifier_to_kvm(struct mmu_notifier *mn) > > { > > @@ -714,45 +770,6 @@ static void kvm_mmu_notifier_change_pte(struct mmu_notifier *mn, > > kvm_handle_hva_range(mn, address, address + 1, pte, kvm_set_spte_gfn); > > } > > > > -void kvm_mmu_invalidate_begin(struct kvm *kvm) > > -{ > > - /* > > - * The count increase must become visible at unlock time as no > > - * spte can be established without taking the mmu_lock and > > - * count is also read inside the mmu_lock critical section. > > - */ > > - kvm->mmu_invalidate_in_progress++; > > - > > - if (likely(kvm->mmu_invalidate_in_progress == 1)) { > > - kvm->mmu_invalidate_range_start = INVALID_GPA; > > - kvm->mmu_invalidate_range_end = INVALID_GPA; > > - } > > -} > > - > > -void kvm_mmu_invalidate_range_add(struct kvm *kvm, gfn_t start, gfn_t end) > > -{ > > - WARN_ON_ONCE(!kvm->mmu_invalidate_in_progress); > > - > > - if (likely(kvm->mmu_invalidate_in_progress == 1)) { > > - kvm->mmu_invalidate_range_start = start; > > - kvm->mmu_invalidate_range_end = end; > > - } else { > > - /* > > - * Fully tracking multiple concurrent ranges has diminishing > > - * returns. Keep things simple and just find the minimal range > > - * which includes the current and new ranges. As there won't be > > - * enough information to subtract a range after its invalidate > > - * completes, any ranges invalidated concurrently will > > - * accumulate and persist until all outstanding invalidates > > - * complete. > > - */ > > - kvm->mmu_invalidate_range_start = > > - min(kvm->mmu_invalidate_range_start, start); > > - kvm->mmu_invalidate_range_end = > > - max(kvm->mmu_invalidate_range_end, end); > > - } > > -} > > - > > static bool kvm_mmu_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range) > > { > > kvm_mmu_invalidate_range_add(kvm, range->start, range->end); > > @@ -806,23 +823,6 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn, > > return 0; > > } > > > > -void kvm_mmu_invalidate_end(struct kvm *kvm) > > -{ > > - /* > > - * This sequence increase will notify the kvm page fault that > > - * the page that is going to be mapped in the spte could have > > - * been freed. > > - */ > > - kvm->mmu_invalidate_seq++; > > - smp_wmb(); > > - /* > > - * The above sequence increase must be visible before the > > - * below count decrease, which is ensured by the smp_wmb above > > - * in conjunction with the smp_rmb in mmu_invalidate_retry(). > > - */ > > - kvm->mmu_invalidate_in_progress--; > > -} > > - > > static void kvm_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn, > > const struct mmu_notifier_range *range) > > { > > @@ -1140,6 +1140,11 @@ int __weak kvm_arch_create_vm_debugfs(struct kvm *kvm) > > return 0; > > } > > > > +bool __weak kvm_arch_has_private_mem(struct kvm *kvm) > > +{ > > + return false; > > +} > > + > > static struct kvm *kvm_create_vm(unsigned long type, const char *fdname) > > { > > struct kvm *kvm = kvm_arch_alloc_vm(); > > @@ -2349,15 +2354,47 @@ static u64 kvm_supported_mem_attributes(struct kvm *kvm) > > return 0; > > } > > > > +static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end) > > +{ > > + struct kvm_gfn_range gfn_range; > > + struct kvm_memory_slot *slot; > > + struct kvm_memslots *slots; > > + struct kvm_memslot_iter iter; > > + int i; > > + int r = 0; > > + > > + gfn_range.pte = __pte(0); > > + gfn_range.may_block = true; > > + > > + for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) { > > + slots = __kvm_memslots(kvm, i); > > + > > + kvm_for_each_memslot_in_gfn_range(&iter, slots, start, end) { > > + slot = iter.slot; > > + gfn_range.start = max(start, slot->base_gfn); > > + gfn_range.end = min(end, slot->base_gfn + slot->npages); > > + if (gfn_range.start >= gfn_range.end) > > + continue; > > + gfn_range.slot = slot; > > + > > + r |= kvm_unmap_gfn_range(kvm, &gfn_range); > > + } > > + } > > + > > + if (r) > > + kvm_flush_remote_tlbs(kvm); > > +} > > + > > static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm, > > struct kvm_memory_attributes *attrs) > > { > > gfn_t start, end; > > unsigned long i; > > void *entry; > > + int idx; > > u64 supported_attrs = kvm_supported_mem_attributes(kvm); > > > > - /* flags is currently not used. */ > > + /* 'flags' is currently not used. */ > > if (attrs->flags) > > return -EINVAL; > > if (attrs->attributes & ~supported_attrs) > > @@ -2372,6 +2409,13 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm, > > > > entry = attrs->attributes ? xa_mk_value(attrs->attributes) : NULL; > > > > + if (kvm_arch_has_private_mem(kvm)) { > > + KVM_MMU_LOCK(kvm); > > + kvm_mmu_invalidate_begin(kvm); > > + kvm_mmu_invalidate_range_add(kvm, start, end); > > + KVM_MMU_UNLOCK(kvm); > > + } > > + > > mutex_lock(&kvm->lock); > > for (i = start; i < end; i++) > > if (xa_err(xa_store(&kvm->mem_attr_array, i, entry, > > @@ -2379,6 +2423,16 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm, > > break; > > mutex_unlock(&kvm->lock); > > > > + if (kvm_arch_has_private_mem(kvm)) { > > + idx = srcu_read_lock(&kvm->srcu); > > + KVM_MMU_LOCK(kvm); > > + if (i > start) > > + kvm_unmap_mem_range(kvm, start, i); > > + kvm_mmu_invalidate_end(kvm); > > + KVM_MMU_UNLOCK(kvm); > > + srcu_read_unlock(&kvm->srcu, idx); > > + } > > + > > attrs->address = i << PAGE_SHIFT; > > attrs->size = (end - i) << PAGE_SHIFT; > > > > -- > > 2.25.1 > >