From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7A8E717BD3 for ; Wed, 21 May 2025 07:48:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747813731; cv=none; b=I4RU93739aEeiJlLCutpQdb96JdreETppFWrK7UqpfnF6g7wwUWLvKS+KsgQQphFSyhJhReMSfTYtoVNZt+V9MMaiCjXJtCI+xIw7fsiFA7RMnhW3iQDWEbK59pFa9qnhkUzd+jSWF5+OoUPg+KeQM+IzSXkku7C8BVEtG+O27g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747813731; c=relaxed/simple; bh=Dpy1obNg3DJawKTfV5amUEt0pWwh1Uj+CHxe44BgZGM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=R3mB0zis8Ty2FWGyHfDxAHNWvB+wA3m87MtBg5klC6pjOCwMOHsu7EYxwPCo7aOAStqKRJPashFpSVLcbujMKuwDkJIf8tDE9FSQzMIQo4Xv50Dlk9lXsk9QYWkmM1DCvVpLqJA6aYHNc78irRygDXvr8m6ZR8OqMzu/4wBTTsA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=P8BWr8n/; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="P8BWr8n/" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1747813728; h=from:from: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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=Ak0FpZpQGUq4r2jLBIWnnDK9APkUfaLBmd+ZS8A7nGU=; b=P8BWr8n/Zteu97BGv6pW/LbORIjpOo6crHzpS66b/K6II4nUyanfaYf5YjyUqa4cIVvZF5 reApzSiUkPfahZm/NT7mxKicrO7NOGkx45K4ArjP4J0WoBTOvrAHrafm8lkpujM7uO15on OGRsrSLPo4WbAY6gVbRxXCvq6CvVTrI= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-623-MdbjJkHfOpWpForgS-UENQ-1; Wed, 21 May 2025 03:48:46 -0400 X-MC-Unique: MdbjJkHfOpWpForgS-UENQ-1 X-Mimecast-MFC-AGG-ID: MdbjJkHfOpWpForgS-UENQ_1747813726 Received: by mail-wr1-f70.google.com with SMTP id ffacd0b85a97d-3a36bbfbd96so1598032f8f.0 for ; Wed, 21 May 2025 00:48:46 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1747813726; x=1748418526; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=Ak0FpZpQGUq4r2jLBIWnnDK9APkUfaLBmd+ZS8A7nGU=; b=MtBKNafI69TxC/JL4ibLwJUktafbL7s4dLhwPXZZ0UPbgbRe7wzj4trblp0ECZ3DWe IvVxT6qsh3trYTPARbKGl9HM/f7MP2WziUcD2Gyh2LoAX2ZauZL3ZoNQy2ZNrtTHisYa i73k6N6JB0/Np80gp90j01r6IwCX3uY5qUoIpYlUvkl0RnzE/aj1VxA5D+dcpHBgJCTB pHn5wC1wI9TqgdZgdgDpwf28vPYZ/XNnAbCXhV4WLi/foc/Wbm+6WPca+Gtv/9CUTdQ3 NL7uyGZFBFSm2VQ66rT2AVCspaj6RQV2tkx8I2tcvBD+mmZr/Hqa+72XApdKracQ0JdY Q00Q== X-Forwarded-Encrypted: i=1; AJvYcCU9smX3B/FFui4cVBPMt4JYKUiJjtdWOTVIBSI5+7eTFO/BBvWOwGcSGo19Lfx7FcLxGdlnZ0MeHF/geV/o@vger.kernel.org X-Gm-Message-State: AOJu0Yxv8huH9g/5zDJR8IWnlqDFp35/pnZMdOBFy8+1OMXwYfSRWLqd wJgcBDMNPjqyOD4njBWGsYORgy4eIhwaFCnuBx5r4NFyuiZKNk9qjz1UHGcQ/sFu2kSjqURIM25 gfvucM2yoYW3LXB6wxuN6IgDVeARDlvY7KSORL22yZkDUwTgBsHh/rwcuC4FI6PVlEEI= X-Gm-Gg: ASbGncuHZWKJaMtUWZD6fckxYdsci0/ubc+Z+AE/fvjHvHMyefqSCrLGY6Rg4dbmAnE qsLQtHlwui4XRQj1/O2E/fFVB9Cv7xo4F33AaqkzrhFn/fa1gMknti5bY3aU/G6ASn0MnhhKXoT Xg5vLs3NCfV8qZ8dOSaW00Ptv/6GhLKPAjdiY65uqrQv1zaXW+kzhBKbKilGMZgiQIcnxFUa+IM ntoDL6s0/gZXIqEqVux2g0KuOE+aBAG4cSpjXLvOxJn6fl0iq5wuZL9LfOIOP3+FIq1aO/SPXo0 /qLQm5WXvPt4WtOvmqgVH1nXTMdoA3N70JFLFUxpKc3NpIvWu/qMseIHuCbJnntbsWV/sF4DY6K tVLeM3SXdEDLUCd75E21AxvVc2stitJegNIqYzdc= X-Received: by 2002:a5d:5846:0:b0:3a3:77d7:b200 with SMTP id ffacd0b85a97d-3a377d7b217mr6057046f8f.17.1747813725528; Wed, 21 May 2025 00:48:45 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEpTN9e/ZWesBOJXUvFSgL0EPyX/uv1m4Z6LW50+xiHAoT/yoWtj3ovu6uQ/k6pLY3iXDGoKQ== X-Received: by 2002:a5d:5846:0:b0:3a3:77d7:b200 with SMTP id ffacd0b85a97d-3a377d7b217mr6057003f8f.17.1747813725052; Wed, 21 May 2025 00:48:45 -0700 (PDT) Received: from ?IPV6:2003:d8:2f25:9c00:e2c7:6eb5:8a51:1c60? (p200300d82f259c00e2c76eb58a511c60.dip0.t-ipconnect.de. [2003:d8:2f25:9c00:e2c7:6eb5:8a51:1c60]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a35ca88735sm19296243f8f.69.2025.05.21.00.48.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 21 May 2025 00:48:44 -0700 (PDT) Message-ID: Date: Wed, 21 May 2025 09:48:41 +0200 Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 09/17] KVM: x86/mmu: Handle guest page faults for guest_memfd with shared memory To: Fuad Tabba , kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org Cc: pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com, peterx@redhat.com, pankaj.gupta@amd.com, ira.weiny@intel.com References: <20250513163438.3942405-1-tabba@google.com> <20250513163438.3942405-10-tabba@google.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <20250513163438.3942405-10-tabba@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 13.05.25 18:34, Fuad Tabba wrote: > From: Ackerley Tng > > For memslots backed by guest_memfd with shared mem support, the KVM MMU > always faults-in pages from guest_memfd, and not from the userspace_addr. > Towards this end, this patch also introduces a new guest_memfd flag, > GUEST_MEMFD_FLAG_SUPPORT_SHARED, which indicates that the guest_memfd > instance supports in-place shared memory. > > This flag is only supported if the VM creating the guest_memfd instance > belongs to certain types determined by architecture. Only non-CoCo VMs > are permitted to use guest_memfd with shared mem, for now. > > Function names have also been updated for accuracy - > kvm_mem_is_private() returns true only when the current private/shared > state (in the CoCo sense) of the memory is private, and returns false if > the current state is shared explicitly or impicitly, e.g., belongs to a > non-CoCo VM. > > kvm_mmu_faultin_pfn_gmem() is updated to indicate that it can be used > to fault in not just private memory, but more generally, from > guest_memfd. > > Co-developed-by: Fuad Tabba > Signed-off-by: Fuad Tabba > Co-developed-by: David Hildenbrand > Signed-off-by: David Hildenbrand > Signed-off-by: Ackerley Tng > --- [...] > + > #ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES > static inline unsigned long kvm_get_memory_attributes(struct kvm *kvm, gfn_t gfn) > { > @@ -2515,10 +2524,30 @@ bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm, > bool kvm_arch_post_set_memory_attributes(struct kvm *kvm, > struct kvm_gfn_range *range); > > +/* > + * Returns true if the given gfn's private/shared status (in the CoCo sense) is > + * private. > + * > + * A return value of false indicates that the gfn is explicitly or implicity s/implicity/implicitly/ > + * shared (i.e., non-CoCo VMs). > + */ > static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) > { > - return IS_ENABLED(CONFIG_KVM_GMEM) && > - kvm_get_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE; > + struct kvm_memory_slot *slot; > + > + if (!IS_ENABLED(CONFIG_KVM_GMEM)) > + return false; > + > + slot = gfn_to_memslot(kvm, gfn); > + if (kvm_slot_has_gmem(slot) && kvm_gmem_memslot_supports_shared(slot)) { > + /* > + * For now, memslots only support in-place shared memory if the > + * host is allowed to mmap memory (i.e., non-Coco VMs). > + */ Not accurate: there is no in-place conversion support in this series, because there is no such itnerface. So the reason is that all memory is shared for there VM types? > + return false; > + } > + > + return kvm_get_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE; > } > #else > static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > index 2f499021df66..fe0245335c96 100644 > --- a/virt/kvm/guest_memfd.c > +++ b/virt/kvm/guest_memfd.c > @@ -388,6 +388,23 @@ static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma) > > return 0; > } > + > +bool kvm_gmem_memslot_supports_shared(const struct kvm_memory_slot *slot) > +{ > + struct file *file; > + bool ret; > + > + file = kvm_gmem_get_file((struct kvm_memory_slot *)slot); > + if (!file) > + return false; > + > + ret = kvm_gmem_supports_shared(file_inode(file)); > + > + fput(file); > + return ret; Would it make sense to cache that information in the memslot, to avoid the get/put? We could simply cache when creating the memslot I guess. As an alternative ... could we simple get/put when managing the memslot? -- Cheers, David / dhildenb