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 902E7C352A1 for ; Tue, 6 Dec 2022 12:07:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234545AbiLFMH3 (ORCPT ); Tue, 6 Dec 2022 07:07:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60394 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235334AbiLFMHC (ORCPT ); Tue, 6 Dec 2022 07:07:02 -0500 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 437D1E01A; Tue, 6 Dec 2022 04:06:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1670328419; x=1701864419; h=date:from:to:cc:subject:message-id:reply-to:references: mime-version:in-reply-to; bh=/9rw4XJZnVf887NtG425skKbwwHseWVQy8ohNx+mMzU=; b=c9TY9mo6D9vYu8x8bbEhse+QFYFsISWdZ7OB+Gh5zr8fPqqb/vVX/Vxa 9kHPS4Borq24C1tND8K3wQ19TjaReZLLKf4ijn9Kvq3J5yha44BGxojhD fgBXBI7ScF/fHvJSfy6eriXZXSaTr9sZpW5Q9/1jsG8KPgVOykdgW5nIk T/vd1YXBjAQXFn85BRLhJRtdkm1Eur7vD7ZOqXSWa/ynH7mc7+reBJso/ LqQZzjrI4GXhR+COmZ2B9ytgWfhYmEDtp4tQiDswwyjDVftUEHG1jZNwB 87bFsCBmeiGOMiE9ROZl9OAUqkGDRgG4Jr4YrEA14vayo8HMsSRSRveNf g==; X-IronPort-AV: E=McAfee;i="6500,9779,10552"; a="317748801" X-IronPort-AV: E=Sophos;i="5.96,222,1665471600"; d="scan'208";a="317748801" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Dec 2022 04:06:58 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10552"; a="639853305" X-IronPort-AV: E=Sophos;i="5.96,222,1665471600"; d="scan'208";a="639853305" Received: from chaop.bj.intel.com (HELO localhost) ([10.240.193.75]) by orsmga007.jf.intel.com with ESMTP; 06 Dec 2022 04:06:44 -0800 Date: Tue, 6 Dec 2022 20:02:24 +0800 From: Chao Peng To: Isaku Yamahata 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 , tabba@google.com, Michael Roth , mhocko@suse.com, wei.w.wang@intel.com Subject: Re: [PATCH v10 7/9] KVM: Update lpage info when private/shared memory are mixed Message-ID: <20221206120224.GC1216605@chaop.bj.intel.com> Reply-To: Chao Peng References: <20221202061347.1070246-1-chao.p.peng@linux.intel.com> <20221202061347.1070246-8-chao.p.peng@linux.intel.com> <20221205224959.GA3632095@ls.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221205224959.GA3632095@ls.amr.corp.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 05, 2022 at 02:49:59PM -0800, Isaku Yamahata wrote: > On Fri, Dec 02, 2022 at 02:13:45PM +0800, > Chao Peng wrote: > > > A large page with mixed private/shared subpages can't be mapped as large > > page since its sub private/shared pages are from different memory > > backends and may also treated by architecture differently. When > > private/shared memory are mixed in a large page, the current lpage_info > > is not sufficient to decide whether the page can be mapped as large page > > or not and additional private/shared mixed information is needed. > > > > Tracking this 'mixed' information with the current 'count' like > > disallow_lpage is a bit challenge so reserve a bit in 'disallow_lpage' > > to indicate a large page has mixed private/share subpages and update > > this 'mixed' bit whenever the memory attribute is changed between > > private and shared. > > > > Signed-off-by: Chao Peng > > --- > > arch/x86/include/asm/kvm_host.h | 8 ++ > > arch/x86/kvm/mmu/mmu.c | 134 +++++++++++++++++++++++++++++++- > > arch/x86/kvm/x86.c | 2 + > > include/linux/kvm_host.h | 19 +++++ > > virt/kvm/kvm_main.c | 9 ++- > > 5 files changed, 169 insertions(+), 3 deletions(-) > > > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > > index 283cbb83d6ae..7772ab37ac89 100644 > > --- a/arch/x86/include/asm/kvm_host.h > > +++ b/arch/x86/include/asm/kvm_host.h > > @@ -38,6 +38,7 @@ > > #include > > > > #define __KVM_HAVE_ARCH_VCPU_DEBUGFS > > +#define __KVM_HAVE_ARCH_SET_MEMORY_ATTRIBUTES > > > > #define KVM_MAX_VCPUS 1024 > > > > @@ -1011,6 +1012,13 @@ struct kvm_vcpu_arch { > > #endif > > }; > > > > +/* > > + * Use a bit in disallow_lpage to indicate private/shared pages mixed at the > > + * level. The remaining bits are used as a reference count. > > + */ > > +#define KVM_LPAGE_PRIVATE_SHARED_MIXED (1U << 31) > > +#define KVM_LPAGE_COUNT_MAX ((1U << 31) - 1) > > + > > struct kvm_lpage_info { > > int disallow_lpage; > > }; > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > > index e2c70b5afa3e..2190fd8c95c0 100644 > > --- a/arch/x86/kvm/mmu/mmu.c > > +++ b/arch/x86/kvm/mmu/mmu.c > > @@ -763,11 +763,16 @@ static void update_gfn_disallow_lpage_count(const struct kvm_memory_slot *slot, > > { > > struct kvm_lpage_info *linfo; > > int i; > > + int disallow_count; > > > > for (i = PG_LEVEL_2M; i <= KVM_MAX_HUGEPAGE_LEVEL; ++i) { > > linfo = lpage_info_slot(gfn, slot, i); > > + > > + disallow_count = linfo->disallow_lpage & KVM_LPAGE_COUNT_MAX; > > + WARN_ON(disallow_count + count < 0 || > > + disallow_count > KVM_LPAGE_COUNT_MAX - count); > > + > > linfo->disallow_lpage += count; > > - WARN_ON(linfo->disallow_lpage < 0); > > } > > } > > > > @@ -6986,3 +6991,130 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm) > > if (kvm->arch.nx_huge_page_recovery_thread) > > kthread_stop(kvm->arch.nx_huge_page_recovery_thread); > > } > > + > > +static bool linfo_is_mixed(struct kvm_lpage_info *linfo) > > +{ > > + return linfo->disallow_lpage & KVM_LPAGE_PRIVATE_SHARED_MIXED; > > +} > > + > > +static void linfo_set_mixed(gfn_t gfn, struct kvm_memory_slot *slot, > > + int level, bool mixed) > > +{ > > + struct kvm_lpage_info *linfo = lpage_info_slot(gfn, slot, level); > > + > > + if (mixed) > > + linfo->disallow_lpage |= KVM_LPAGE_PRIVATE_SHARED_MIXED; > > + else > > + linfo->disallow_lpage &= ~KVM_LPAGE_PRIVATE_SHARED_MIXED; > > +} > > + > > +static bool is_expected_attr_entry(void *entry, unsigned long expected_attrs) > > +{ > > + bool expect_private = expected_attrs & KVM_MEMORY_ATTRIBUTE_PRIVATE; > > + > > + if (xa_to_value(entry) & KVM_MEMORY_ATTRIBUTE_PRIVATE) { > > + if (!expect_private) > > + return false; > > + } else if (expect_private) > > + return false; > > + > > + return true; > > +} > > + > > +static bool mem_attrs_mixed_2m(struct kvm *kvm, unsigned long attrs, > > + gfn_t start, gfn_t end) > > +{ > > + XA_STATE(xas, &kvm->mem_attr_array, start); > > + gfn_t gfn = start; > > + void *entry; > > + bool mixed = false; > > + > > + rcu_read_lock(); > > + entry = xas_load(&xas); > > + while (gfn < end) { > > + if (xas_retry(&xas, entry)) > > + continue; > > + > > + KVM_BUG_ON(gfn != xas.xa_index, kvm); > > + > > + if (!is_expected_attr_entry(entry, attrs)) { > > + mixed = true; > > + break; > > + } > > + > > + entry = xas_next(&xas); > > + gfn++; > > + } > > + > > + rcu_read_unlock(); > > + return mixed; > > +} > > + > > +static bool mem_attrs_mixed(struct kvm *kvm, struct kvm_memory_slot *slot, > > + int level, unsigned long attrs, > > + gfn_t start, gfn_t end) > > +{ > > + unsigned long gfn; > > + > > + if (level == PG_LEVEL_2M) > > + return mem_attrs_mixed_2m(kvm, attrs, start, end); > > + > > + for (gfn = start; gfn < end; gfn += KVM_PAGES_PER_HPAGE(level - 1)) > > + if (linfo_is_mixed(lpage_info_slot(gfn, slot, level - 1)) || > > + !is_expected_attr_entry(xa_load(&kvm->mem_attr_array, gfn), > > + attrs)) > > + return true; > > + return false; > > +} > > + > > +static void kvm_update_lpage_private_shared_mixed(struct kvm *kvm, > > + struct kvm_memory_slot *slot, > > + unsigned long attrs, > > + gfn_t start, gfn_t end) > > +{ > > + unsigned long pages, mask; > > + gfn_t gfn, gfn_end, first, last; > > + int level; > > + bool mixed; > > + > > + /* > > + * The sequence matters here: we set the higher level basing on the > > + * lower level's scanning result. > > + */ > > + for (level = PG_LEVEL_2M; level <= KVM_MAX_HUGEPAGE_LEVEL; level++) { > > + pages = KVM_PAGES_PER_HPAGE(level); > > + mask = ~(pages - 1); > > + first = start & mask; > > + last = (end - 1) & mask; > > + > > + /* > > + * We only need to scan the head and tail page, for middle pages > > + * we know they will not be mixed. > > + */ > > + gfn = max(first, slot->base_gfn); > > + gfn_end = min(first + pages, slot->base_gfn + slot->npages); > > + mixed = mem_attrs_mixed(kvm, slot, level, attrs, gfn, gfn_end); > > + linfo_set_mixed(gfn, slot, level, mixed); > > + > > + if (first == last) > > + return; > > > continue. Ya! > > > + > > + for (gfn = first + pages; gfn < last; gfn += pages) > > + linfo_set_mixed(gfn, slot, level, false); > > + > > + gfn = last; > > + gfn_end = min(last + pages, slot->base_gfn + slot->npages); > > if (gfn == gfn_end) continue. Do you see a case where gfn can equal to gfn_end? Though it does not hurt to add a check. > > > > + mixed = mem_attrs_mixed(kvm, slot, level, attrs, gfn, gfn_end); > > + linfo_set_mixed(gfn, slot, level, mixed); > > + } > > +} > > + > > +void kvm_arch_set_memory_attributes(struct kvm *kvm, > > + struct kvm_memory_slot *slot, > > + unsigned long attrs, > > + gfn_t start, gfn_t end) > > +{ > > + if (kvm_slot_can_be_private(slot)) > > + kvm_update_lpage_private_shared_mixed(kvm, slot, attrs, > > + start, end); > > +} > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > index 9a07380f8d3c..5aefcff614d2 100644 > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -12362,6 +12362,8 @@ static int kvm_alloc_memslot_metadata(struct kvm *kvm, > > if ((slot->base_gfn + npages) & (KVM_PAGES_PER_HPAGE(level) - 1)) > > linfo[lpages - 1].disallow_lpage = 1; > > ugfn = slot->userspace_addr >> PAGE_SHIFT; > > + if (kvm_slot_can_be_private(slot)) > > + ugfn |= slot->restricted_offset >> PAGE_SHIFT; > > Is there any alignment restriction? If no, It should be +=. > In practice, alignment will hold though. All we need here is checking whether both userspace_addr and restricted_offset are aligned to HPAGE_SIZE or not. '+=' actually can yield wrong value in cases when userspace_addr + restricted_offset is aligned to HPAGE_SIZE but individually they may not align to HPAGE_SIZE. Thanks, Chao > > Thanks, > > > /* > > * If the gfn and userspace address are not aligned wrt each > > * other, disable large page support for this slot. > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index 3331c0c92838..25099c94e770 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -592,6 +592,11 @@ struct kvm_memory_slot { > > struct restrictedmem_notifier notifier; > > }; > > > > +static inline bool kvm_slot_can_be_private(const struct kvm_memory_slot *slot) > > +{ > > + return slot && (slot->flags & KVM_MEM_PRIVATE); > > +} > > + > > static inline bool kvm_slot_dirty_track_enabled(const struct kvm_memory_slot *slot) > > { > > return slot->flags & KVM_MEM_LOG_DIRTY_PAGES; > > @@ -2316,4 +2321,18 @@ static inline void kvm_account_pgtable_pages(void *virt, int nr) > > /* Max number of entries allowed for each kvm dirty ring */ > > #define KVM_DIRTY_RING_MAX_ENTRIES 65536 > > > > +#ifdef __KVM_HAVE_ARCH_SET_MEMORY_ATTRIBUTES > > +void kvm_arch_set_memory_attributes(struct kvm *kvm, > > + struct kvm_memory_slot *slot, > > + unsigned long attrs, > > + gfn_t start, gfn_t end); > > +#else > > +static inline void kvm_arch_set_memory_attributes(struct kvm *kvm, > > + struct kvm_memory_slot *slot, > > + unsigned long attrs, > > + gfn_t start, gfn_t end) > > +{ > > +} > > +#endif /* __KVM_HAVE_ARCH_SET_MEMORY_ATTRIBUTES */ > > + > > #endif > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > > index 4e1e1e113bf0..e107afea32f0 100644 > > --- a/virt/kvm/kvm_main.c > > +++ b/virt/kvm/kvm_main.c > > @@ -2354,7 +2354,8 @@ 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) > > +static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end, > > + unsigned long attrs) > > { > > struct kvm_gfn_range gfn_range; > > struct kvm_memory_slot *slot; > > @@ -2378,6 +2379,10 @@ static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end) > > gfn_range.slot = slot; > > > > r |= kvm_unmap_gfn_range(kvm, &gfn_range); > > + > > + kvm_arch_set_memory_attributes(kvm, slot, attrs, > > + gfn_range.start, > > + gfn_range.end); > > } > > } > > > > @@ -2427,7 +2432,7 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm, > > idx = srcu_read_lock(&kvm->srcu); > > KVM_MMU_LOCK(kvm); > > if (i > start) > > - kvm_unmap_mem_range(kvm, start, i); > > + kvm_unmap_mem_range(kvm, start, i, attrs->attributes); > > kvm_mmu_invalidate_end(kvm); > > KVM_MMU_UNLOCK(kvm); > > srcu_read_unlock(&kvm->srcu, idx); > > -- > > 2.25.1 > > > > -- > Isaku Yamahata