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 7A2A9C4321E for ; Mon, 5 Dec 2022 09:24:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230480AbiLEJYc (ORCPT ); Mon, 5 Dec 2022 04:24:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44532 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230307AbiLEJYa (ORCPT ); Mon, 5 Dec 2022 04:24:30 -0500 Received: from mail-lf1-x12f.google.com (mail-lf1-x12f.google.com [IPv6:2a00:1450:4864:20::12f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 718F01741F for ; Mon, 5 Dec 2022 01:24:28 -0800 (PST) Received: by mail-lf1-x12f.google.com with SMTP id s8so17571386lfc.8 for ; Mon, 05 Dec 2022 01:24:28 -0800 (PST) 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:message-id:reply-to; bh=Owo0phbbJOrq6sWBiQ2bW5Gab2bMQcmAUmytHNbH9wo=; b=CBfUM4ABoy4rHbnJbQWlgFZPr36WGkyWiutGX6w63I8DmF/IJiild6FcVSNN7OWJZ7 pXxUiVma9yq+PhDIrUun9M9Va0gKBpKxjzL4hSd+yyVkziX/hM+hdNnS2HrixHqWqr+w 9uPS+gbUSproyB0am3JO8sKBKWWHQ/lzz53ju3Q567AM4L0/1VsnFw7a7e+xLX5dqtAL ltPfrvJFTtJCH5f/cWONsgU7aRsJDDYFPsxECnuUV1Upx768mYuIz8CszK1XiyhlQVRZ mn1NjlqoOAVwrxhEaj2jBzLXfvyd3qLezPV3GfuypCofEI10LU/+uMeT5vEdTm2OxrYD evrA== 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:message-id :reply-to; bh=Owo0phbbJOrq6sWBiQ2bW5Gab2bMQcmAUmytHNbH9wo=; b=EqmBC4E4VNKfQVyCucXGBu8R5+X9PwXnYDAp+YBt3tN9Oj02k7fEsMcYdpmPuu7Cfy INxu0xKyJsjLfPXG1eZhOagi0gQMMrYiX00J7vkghEsDa60nsacwisTVJq0un28UgFpb 73E8diS52NYjyEMys+8HjYnvcTl2JWM6OqDcq6u38EOijwfva176KwANbkfMh5QBsPDy lVlEVm+xCGkWZe099TcW5uu5QGHw+wQkLW03NWBubaakpQmqHM/R4K916LVfH6USFm9O yjkhZSpKrRioULIvbZNFmj6pcs75GkbLJ3ycx5a0jh7MAOdhUeDdV6gMcC1xnnbVYf76 vBSg== X-Gm-Message-State: ANoB5pmZPIrDsAzBfFVHV6p2mliYpnamMDnut6ORQeLbiVdo0yzkcQaS aGYhzZMZm1zkS5FtxMcyebj2rTnjsYIGZARmnHzsQg== X-Google-Smtp-Source: AA0mqf7hmc7cmV5dRxw88/fxJnTLIThfoQtt0oTYjymTMQQZpTJzvpZeXdF6ZMUHCf5Dbxm0DrPC0sEiLurEnocH1bU= X-Received: by 2002:a05:6512:104e:b0:4b5:604a:5b24 with SMTP id c14-20020a056512104e00b004b5604a5b24mr2898439lfb.550.1670232266434; Mon, 05 Dec 2022 01:24:26 -0800 (PST) MIME-Version: 1.0 References: <20221202061347.1070246-1-chao.p.peng@linux.intel.com> <20221202061347.1070246-6-chao.p.peng@linux.intel.com> In-Reply-To: <20221202061347.1070246-6-chao.p.peng@linux.intel.com> From: Fuad Tabba Date: Mon, 5 Dec 2022 09:23:49 +0000 Message-ID: Subject: Re: [PATCH v10 5/9] KVM: Use gfn instead of hva for mmu_notifier_retry To: Chao Peng 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 Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org Hi Chao, On Fri, Dec 2, 2022 at 6:19 AM Chao Peng wrote: > > Currently in mmu_notifier invalidate path, hva range is recorded and > then checked against by mmu_notifier_retry_hva() in the page fault > handling path. However, for the to be introduced private memory, a page > fault may not have a hva associated, checking gfn(gpa) makes more sense. > > For existing hva based shared memory, gfn is expected to also work. The > only downside is when aliasing multiple gfns to a single hva, the > current algorithm of checking multiple ranges could result in a much > larger range being rejected. Such aliasing should be uncommon, so the > impact is expected small. > > Suggested-by: Sean Christopherson > Signed-off-by: Chao Peng > --- > arch/x86/kvm/mmu/mmu.c | 8 +++++--- > include/linux/kvm_host.h | 33 +++++++++++++++++++++------------ > virt/kvm/kvm_main.c | 32 +++++++++++++++++++++++--------- > 3 files changed, 49 insertions(+), 24 deletions(-) > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 4736d7849c60..e2c70b5afa3e 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -4259,7 +4259,7 @@ static bool is_page_fault_stale(struct kvm_vcpu *vcpu, > return true; > > return fault->slot && > - mmu_invalidate_retry_hva(vcpu->kvm, mmu_seq, fault->hva); > + mmu_invalidate_retry_gfn(vcpu->kvm, mmu_seq, fault->gfn); > } > > static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) > @@ -6098,7 +6098,9 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end) > > write_lock(&kvm->mmu_lock); > > - kvm_mmu_invalidate_begin(kvm, gfn_start, gfn_end); > + kvm_mmu_invalidate_begin(kvm); > + > + kvm_mmu_invalidate_range_add(kvm, gfn_start, gfn_end); > > flush = kvm_rmap_zap_gfn_range(kvm, gfn_start, gfn_end); > > @@ -6112,7 +6114,7 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end) > kvm_flush_remote_tlbs_with_address(kvm, gfn_start, > gfn_end - gfn_start); > > - kvm_mmu_invalidate_end(kvm, gfn_start, gfn_end); > + kvm_mmu_invalidate_end(kvm); > > write_unlock(&kvm->mmu_lock); > } > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 02347e386ea2..3d69484d2704 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -787,8 +787,8 @@ struct kvm { > struct mmu_notifier mmu_notifier; > unsigned long mmu_invalidate_seq; > long mmu_invalidate_in_progress; > - unsigned long mmu_invalidate_range_start; > - unsigned long mmu_invalidate_range_end; > + gfn_t mmu_invalidate_range_start; > + gfn_t mmu_invalidate_range_end; > #endif > struct list_head devices; > u64 manual_dirty_log_protect; > @@ -1389,10 +1389,9 @@ void kvm_mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc); > void *kvm_mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc); > #endif > > -void kvm_mmu_invalidate_begin(struct kvm *kvm, unsigned long start, > - unsigned long end); > -void kvm_mmu_invalidate_end(struct kvm *kvm, unsigned long start, > - unsigned long end); > +void kvm_mmu_invalidate_begin(struct kvm *kvm); > +void kvm_mmu_invalidate_range_add(struct kvm *kvm, gfn_t start, gfn_t end); > +void kvm_mmu_invalidate_end(struct kvm *kvm); > > long kvm_arch_dev_ioctl(struct file *filp, > unsigned int ioctl, unsigned long arg); > @@ -1963,9 +1962,9 @@ static inline int mmu_invalidate_retry(struct kvm *kvm, unsigned long mmu_seq) > return 0; > } > > -static inline int mmu_invalidate_retry_hva(struct kvm *kvm, > +static inline int mmu_invalidate_retry_gfn(struct kvm *kvm, > unsigned long mmu_seq, > - unsigned long hva) > + gfn_t gfn) > { > lockdep_assert_held(&kvm->mmu_lock); > /* > @@ -1974,10 +1973,20 @@ static inline int mmu_invalidate_retry_hva(struct kvm *kvm, > * that might be being invalidated. Note that it may include some false nit: "might be" (or) "is being" > * positives, due to shortcuts when handing concurrent invalidations. nit: handling > */ > - if (unlikely(kvm->mmu_invalidate_in_progress) && > - hva >= kvm->mmu_invalidate_range_start && > - hva < kvm->mmu_invalidate_range_end) > - return 1; > + if (unlikely(kvm->mmu_invalidate_in_progress)) { > + /* > + * Dropping mmu_lock after bumping mmu_invalidate_in_progress > + * but before updating the range is a KVM bug. > + */ > + if (WARN_ON_ONCE(kvm->mmu_invalidate_range_start == INVALID_GPA || > + kvm->mmu_invalidate_range_end == INVALID_GPA)) INVALID_GPA is an x86-specific define in arch/x86/include/asm/kvm_host.h, so this doesn't build on other architectures. The obvious fix is to move it to include/linux/kvm_host.h. Cheers, /fuad > + return 1; > + > + if (gfn >= kvm->mmu_invalidate_range_start && > + gfn < kvm->mmu_invalidate_range_end) > + return 1; > + } > + > if (kvm->mmu_invalidate_seq != mmu_seq) > return 1; > return 0; > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index b882eb2c76a2..ad55dfbc75d7 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -540,9 +540,7 @@ static void kvm_mmu_notifier_invalidate_range(struct mmu_notifier *mn, > > typedef bool (*hva_handler_t)(struct kvm *kvm, struct kvm_gfn_range *range); > > -typedef void (*on_lock_fn_t)(struct kvm *kvm, unsigned long start, > - unsigned long end); > - > +typedef void (*on_lock_fn_t)(struct kvm *kvm); > typedef void (*on_unlock_fn_t)(struct kvm *kvm); > > struct kvm_hva_range { > @@ -628,7 +626,8 @@ static __always_inline int __kvm_handle_hva_range(struct kvm *kvm, > locked = true; > KVM_MMU_LOCK(kvm); > if (!IS_KVM_NULL_FN(range->on_lock)) > - range->on_lock(kvm, range->start, range->end); > + range->on_lock(kvm); > + > if (IS_KVM_NULL_FN(range->handler)) > break; > } > @@ -715,8 +714,7 @@ 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, unsigned long start, > - unsigned long end) > +void kvm_mmu_invalidate_begin(struct kvm *kvm) > { > /* > * The count increase must become visible at unlock time as no > @@ -724,6 +722,17 @@ void kvm_mmu_invalidate_begin(struct kvm *kvm, unsigned long start, > * 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; > @@ -744,6 +753,12 @@ void kvm_mmu_invalidate_begin(struct kvm *kvm, unsigned long start, > } > } > > +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); > + return kvm_unmap_gfn_range(kvm, range); > +} > + > static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn, > const struct mmu_notifier_range *range) > { > @@ -752,7 +767,7 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn, > .start = range->start, > .end = range->end, > .pte = __pte(0), > - .handler = kvm_unmap_gfn_range, > + .handler = kvm_mmu_unmap_gfn_range, > .on_lock = kvm_mmu_invalidate_begin, > .on_unlock = kvm_arch_guest_memory_reclaimed, > .flush_on_ret = true, > @@ -791,8 +806,7 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn, > return 0; > } > > -void kvm_mmu_invalidate_end(struct kvm *kvm, unsigned long start, > - unsigned long end) > +void kvm_mmu_invalidate_end(struct kvm *kvm) > { > /* > * This sequence increase will notify the kvm page fault that > -- > 2.25.1 >