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[35.230.65.123]) by smtp.gmail.com with ESMTPSA id y1-20020a63ad41000000b003fae8a7e3e5sm4127465pgo.91.2022.06.17.13.52.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Jun 2022 13:52:18 -0700 (PDT) Date: Fri, 17 Jun 2022 20:52:15 +0000 From: Sean Christopherson 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 , 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: 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: <20220519153713.819591-5-chao.p.peng@linux.intel.com> ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1655499140; a=rsa-sha256; cv=none; b=LfPXfIiyLrZwQFnKpF4JAtX8ZU6liu5jWORcLrXBMlx0t1WVc7O7UHvWOR5thosrqbFbR1 VQ3Jl1n81wG/BgbXLmd1YfT9L9zJD4hinQDSLa0Akhkz5kHMV07QyjJ9Jf70sesSkAdKaz pWL2XuPzwnNSxQZKu3YfSV3tPeI0Ndo= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=Tm8fa78A; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf18.hostedemail.com: domain of seanjc@google.com designates 209.85.216.54 as permitted sender) smtp.mailfrom=seanjc@google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1655499140; h=from:from:sender: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=0gvTzgsYSiMbpMdNzx7QQ0trcTLfq0qz6qq+d/xtlqM=; b=fxtDYzVZmwVOpqbx2QfMmj41kjheK5AFOMm5xdyRi9Q6wbrieDzTyzdmfUqDgZt3xeEh+w MXcPIkcWCI+Ffpq6j4SyfKRHzBWq+8nIrQ6VfAS+gGQDwSVt61H4ZSg8ZRjgmN6TaXZbT+ PgZPPbbsZmvsgkQrtYA0z2sJFLV1Gxc= X-Rspamd-Queue-Id: B27841C008E X-Rspam-User: Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=Tm8fa78A; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf18.hostedemail.com: domain of seanjc@google.com designates 209.85.216.54 as permitted sender) smtp.mailfrom=seanjc@google.com X-Rspamd-Server: rspam06 X-Stat-Signature: 8bgaeds6jjpqapws68kw858e98zch6pb X-HE-Tag: 1655499140-840984 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 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. > #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. */ 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. 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 >