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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id F1157C43334 for ; Mon, 20 Jun 2022 14:12:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3F8EF6B0071; Mon, 20 Jun 2022 10:12:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3A7326B0073; Mon, 20 Jun 2022 10:12:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 26F0B8E0001; Mon, 20 Jun 2022 10:12:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 1339A6B0071 for ; Mon, 20 Jun 2022 10:12:18 -0400 (EDT) Received: from smtpin18.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id D2F9B33DB4 for ; Mon, 20 Jun 2022 14:12:17 +0000 (UTC) X-FDA: 79598803914.18.E6458A2 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by imf19.hostedemail.com (Postfix) with ESMTP id A1FF61A0015 for ; Mon, 20 Jun 2022 14:12:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1655734335; x=1687270335; h=date:from:to:cc:subject:message-id:reply-to:references: mime-version:in-reply-to; bh=K/d62gPSVg4NmMutWFje50dPhFVYB3cepmG67K0wcUc=; b=h4nAmSujLEpQjxEWsnpIULJ2zadKscX3TGtSs/EWY+5RHFbnsx4Orjdd I2qIaZ13o6g+zOFSM/Io6MSB7qPizibcL/DesYJRz/XMQZ3P8+qam4JaY 4BsYmfM6Wt25ELBAI0VXA5NnRRI3sbZd2i5I2RGGmuiQ7WUFAnJMWmY5D ksm9qdXlV07YgkIX5qa2AXxDFl0JNz3aiAfw6reLFYmliiRYYT811teGO 8Bj4W9LhwH+wfTypJ/ONpNbf/vClHyiqvmfDSFSkvRDYWtG6eayZVCDRo K/vRX4kOWA99HBlWdD0CpvkO3lJWyVSmsQn7mtUQYjZIGprB5WLKI5NY0 Q==; X-IronPort-AV: E=McAfee;i="6400,9594,10380"; a="343897074" X-IronPort-AV: E=Sophos;i="5.92,306,1650956400"; d="scan'208";a="343897074" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Jun 2022 07:12:12 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.92,306,1650956400"; d="scan'208";a="584911886" Received: from chaop.bj.intel.com (HELO localhost) ([10.240.192.101]) by orsmga007.jf.intel.com with ESMTP; 20 Jun 2022 07:12:02 -0700 Date: Mon, 20 Jun 2022 22:08:41 +0800 From: Chao Peng To: Sean Christopherson 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 , 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 , 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 Subject: Re: [PATCH v6 4/8] KVM: Extend the memslot to support fd-based private memory Message-ID: <20220620140841.GA2016793@chaop.bj.intel.com> Reply-To: Chao Peng References: <20220519153713.819591-1-chao.p.peng@linux.intel.com> <20220519153713.819591-5-chao.p.peng@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=h4nAmSuj; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf19.hostedemail.com: domain of chao.p.peng@linux.intel.com has no SPF policy when checking 134.134.136.100) smtp.mailfrom=chao.p.peng@linux.intel.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1655734336; h=from:from:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=s1NQgRPepO1kegZ1T3S3go1FVn0nVzgQYQcHZacq9dA=; b=Nue4ZmXNvehn/SbqTJaX89vFxZRR/Ts/EfRQrTX4f11SgBdwbvuMDP9IWAlSQbWJrLPnTz EB1RhMgNnp6+4rEgiLERjltObnMgisK8xyaR90csxeGqSKefNUsBhLx4XM+FsOssQQNYOR nnA/2kAMv4qOkzR1ax0ekeCZJScsHIU= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1655734336; a=rsa-sha256; cv=none; b=5UtasvY3DDMM0mq6u8bzUj/DCivxsDM7ox6imq7aZsj6ZeHOE1Qn/NRXSAzdzmt7riyE1K 2Lmn2bOIb235kmnSaurqXPahU2OHwQJXqlMJZynp1p5Y6hKTAmuXDtvxgxjcv4HH/NDX0U gREwRyJMneHeaDWDJ+fQnf8UPdlYp1E= X-Rspamd-Queue-Id: A1FF61A0015 Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=h4nAmSuj; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf19.hostedemail.com: domain of chao.p.peng@linux.intel.com has no SPF policy when checking 134.134.136.100) smtp.mailfrom=chao.p.peng@linux.intel.com X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: p9u7z1at43nrk1ntys7gbqhopasnkmrs X-HE-Tag: 1655734335-475049 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Jun 17, 2022 at 08:52:15PM +0000, Sean Christopherson wrote: > On Thu, May 19, 2022, Chao Peng wrote: > > @@ -653,12 +662,12 @@ struct kvm_irq_routing_table { > > }; > > #endif > > > > -#ifndef KVM_PRIVATE_MEM_SLOTS > > -#define KVM_PRIVATE_MEM_SLOTS 0 > > +#ifndef KVM_INTERNAL_MEM_SLOTS > > +#define KVM_INTERNAL_MEM_SLOTS 0 > > #endif > > This rename belongs in a separate patch. Will separate it out, thanks. > > > #define KVM_MEM_SLOTS_NUM SHRT_MAX > > -#define KVM_USER_MEM_SLOTS (KVM_MEM_SLOTS_NUM - KVM_PRIVATE_MEM_SLOTS) > > +#define KVM_USER_MEM_SLOTS (KVM_MEM_SLOTS_NUM - KVM_INTERNAL_MEM_SLOTS) > > > > #ifndef __KVM_VCPU_MULTIPLE_ADDRESS_SPACE > > static inline int kvm_arch_vcpu_memslots_id(struct kvm_vcpu *vcpu) > > @@ -1087,9 +1096,9 @@ enum kvm_mr_change { > > }; > > > > int kvm_set_memory_region(struct kvm *kvm, > > - const struct kvm_userspace_memory_region *mem); > > + const struct kvm_user_mem_region *mem); > > int __kvm_set_memory_region(struct kvm *kvm, > > - const struct kvm_userspace_memory_region *mem); > > + const struct kvm_user_mem_region *mem); > > void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot); > > void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen); > > int kvm_arch_prepare_memory_region(struct kvm *kvm, > > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > > index e10d131edd80..28cacd3656d4 100644 > > --- a/include/uapi/linux/kvm.h > > +++ b/include/uapi/linux/kvm.h > > @@ -103,6 +103,29 @@ struct kvm_userspace_memory_region { > > __u64 userspace_addr; /* start of the userspace allocated memory */ > > }; > > > > +struct kvm_userspace_memory_region_ext { > > + struct kvm_userspace_memory_region region; > > + __u64 private_offset; > > + __u32 private_fd; > > + __u32 pad1; > > + __u64 pad2[14]; > > +}; > > + > > +#ifdef __KERNEL__ > > +/* Internal helper, the layout must match above user visible structures */ > > It's worth explicity calling out which structureso this aliases. And rather than > add a comment about the layout needing to match that, enforce it in code. I > personally wouldn't bother with an expolicit comment about the layout, IMO that's > a fairly obvious implication of aliasing. > > /* > * kvm_user_mem_region is a kernel-only alias of kvm_userspace_memory_region_ext > * that "unpacks" kvm_userspace_memory_region so that KVM can directly access > * all fields from the top-level "extended" region. > */ > Thanks. > > And I think it's in this patch that you missed a conversion to the alias, in the > prototype for check_memory_region_flags() (looks like it gets fixed up later in > the series). > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 0f81bf0407be..8765b334477d 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -1466,7 +1466,7 @@ static void kvm_replace_memslot(struct kvm *kvm, > } > } > > -static int check_memory_region_flags(const struct kvm_userspace_memory_region *mem) > +static int check_memory_region_flags(const struct kvm_user_mem_region *mem) > { > u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES; > > @@ -4514,6 +4514,33 @@ static int kvm_vm_ioctl_get_stats_fd(struct kvm *kvm) > return fd; > } > > +#define SANITY_CHECK_MEM_REGION_FIELD(field) \ > +do { \ > + BUILD_BUG_ON(offsetof(struct kvm_user_mem_region, field) != \ > + offsetof(struct kvm_userspace_memory_region, field)); \ > + BUILD_BUG_ON(sizeof_field(struct kvm_user_mem_region, field) != \ > + sizeof_field(struct kvm_userspace_memory_region, field)); \ > +} while (0) > + > +#define SANITY_CHECK_MEM_REGION_EXT_FIELD(field) \ > +do { \ > + BUILD_BUG_ON(offsetof(struct kvm_user_mem_region, field) != \ > + offsetof(struct kvm_userspace_memory_region_ext, field)); \ > + BUILD_BUG_ON(sizeof_field(struct kvm_user_mem_region, field) != \ > + sizeof_field(struct kvm_userspace_memory_region_ext, field)); \ > +} while (0) > + > +static void kvm_sanity_check_user_mem_region_alias(void) > +{ > + SANITY_CHECK_MEM_REGION_FIELD(slot); > + SANITY_CHECK_MEM_REGION_FIELD(flags); > + SANITY_CHECK_MEM_REGION_FIELD(guest_phys_addr); > + SANITY_CHECK_MEM_REGION_FIELD(memory_size); > + SANITY_CHECK_MEM_REGION_FIELD(userspace_addr); > + SANITY_CHECK_MEM_REGION_EXT_FIELD(private_offset); > + SANITY_CHECK_MEM_REGION_EXT_FIELD(private_fd); > +} > + > static long kvm_vm_ioctl(struct file *filp, > unsigned int ioctl, unsigned long arg) > { > @@ -4541,6 +4568,8 @@ static long kvm_vm_ioctl(struct file *filp, > unsigned long size; > u32 flags; > > + kvm_sanity_check_user_mem_region_alias(); > + > memset(&mem, 0, sizeof(mem)); > > r = -EFAULT; > > > +struct kvm_user_mem_region { > > + __u32 slot; > > + __u32 flags; > > + __u64 guest_phys_addr; > > + __u64 memory_size; > > + __u64 userspace_addr; > > + __u64 private_offset; > > + __u32 private_fd; > > + __u32 pad1; > > + __u64 pad2[14]; > > +}; > > +#endif > > + > > /* > > * The bit 0 ~ bit 15 of kvm_memory_region::flags are visible for userspace, > > * other bits are reserved for kvm internal use which are defined in > > @@ -110,6 +133,7 @@ struct kvm_userspace_memory_region { > > */ > > #define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0) > > #define KVM_MEM_READONLY (1UL << 1) > > +#define KVM_MEM_PRIVATE (1UL << 2) > > Hmm, KVM_MEM_PRIVATE is technically wrong now that a "private" memslot maps private > and/or shared memory. Strictly speaking, we don't actually need a new flag. Valid > file descriptors must be >=0, so the logic for specifying a memslot that can be > converted between private and shared could be that "(int)private_fd < 0" means > "not convertible", i.e. derive the flag from private_fd. I think a flag is still needed, the problem is private_fd can be safely accessed only when this flag is set, e.g. without this flag, we can't copy_from_user these new fields since they don't exist for previous kvm_userspace_memory_region callers. > > And looking at the two KVM consumers of the flag, via kvm_slot_is_private(), they're > both wrong. Both kvm_faultin_pfn() and kvm_mmu_max_mapping_level() should operate > on the _fault_, not the slot. So it would actually be a positive to not have an easy > way to query if a slot supports conversion. > > > /* for KVM_IRQ_LINE */ > > struct kvm_irq_level { > > ... > > > + if (flags & KVM_MEM_PRIVATE) { > > An added bonus of dropping KVM_MEM_PRIVATE is that these checks go away. > > > + r = -EINVAL; > > + goto out; > > + } > > + > > + size = sizeof(struct kvm_userspace_memory_region); > > + > > + if (copy_from_user(&mem, argp, size)) > > + goto out; > > + > > + r = -EINVAL; > > + if ((flags ^ mem.flags) & KVM_MEM_PRIVATE) > > goto out; > > > > - r = kvm_vm_ioctl_set_memory_region(kvm, &kvm_userspace_mem); > > + r = kvm_vm_ioctl_set_memory_region(kvm, &mem); > > break; > > } > > case KVM_GET_DIRTY_LOG: { > > -- > > 2.25.1 > >