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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E6158CEACF9 for ; Sat, 15 Nov 2025 00:47:01 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 264168E001A; Fri, 14 Nov 2025 19:47:01 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 213BD8E0005; Fri, 14 Nov 2025 19:47:01 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1033A8E001A; Fri, 14 Nov 2025 19:47:01 -0500 (EST) 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 EF2DF8E0005 for ; Fri, 14 Nov 2025 19:47:00 -0500 (EST) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 9543D896F6 for ; Sat, 15 Nov 2025 00:47:00 +0000 (UTC) X-FDA: 84111001800.27.A4139DA Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) by imf22.hostedemail.com (Postfix) with ESMTP id D7B40C000A for ; Sat, 15 Nov 2025 00:46:58 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=lnGdJA6T; spf=pass (imf22.hostedemail.com: domain of 3gc0XaQsKCMoqs0u71uE93ww44w1u.s421y3AD-220Bqs0.47w@flex--ackerleytng.bounces.google.com designates 209.85.216.74 as permitted sender) smtp.mailfrom=3gc0XaQsKCMoqs0u71uE93ww44w1u.s421y3AD-220Bqs0.47w@flex--ackerleytng.bounces.google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1763167618; 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=Mr/52DwIA8Vew8AuO0L8R6bm0vR8dQ+5A9WA+WG6t/s=; b=MzKhbl0GJgb2tKpswU5+fCQ2DOCQleTR9+tpmCn+j5tjIic4iwyXTCz3WM4t9YlXH4HdZw TuFmKNRiyPJKB8ht1bumvXPxSK2faB3B6u1UA3kW9SeQ3wpEPJh6wpNrFbQyDkfT/XAazO WwV1SNM2hij5u5RM5vRuWwD3KtAwiCQ= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1763167619; a=rsa-sha256; cv=none; b=lBudM9AXwRBpvVpQbrfG4bg+GXZw4ybw1hddd61FpjVhSzsqbUnc6eCOHeSBivWLW7PQ8o FVb20izLyNgY11ccL1MkySmeCNN2isghon6Cy7gr/wqk4b18MiiLR+IVXPYdch6UIlHYMh X2ewwXClEezWxbbpfRe5nwI8DnBfXtw= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=lnGdJA6T; spf=pass (imf22.hostedemail.com: domain of 3gc0XaQsKCMoqs0u71uE93ww44w1u.s421y3AD-220Bqs0.47w@flex--ackerleytng.bounces.google.com designates 209.85.216.74 as permitted sender) smtp.mailfrom=3gc0XaQsKCMoqs0u71uE93ww44w1u.s421y3AD-220Bqs0.47w@flex--ackerleytng.bounces.google.com; dmarc=pass (policy=reject) header.from=google.com Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-340bb1bf12aso6171740a91.1 for ; Fri, 14 Nov 2025 16:46:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1763167617; x=1763772417; darn=kvack.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=Mr/52DwIA8Vew8AuO0L8R6bm0vR8dQ+5A9WA+WG6t/s=; b=lnGdJA6TU8eKSKoGa+N80kcWIsNXtzsCB844jEh3HYbic+3LkuOC3TJWYMTMMnA+xN Wn/rdwnMGDG5OQt5+SlCqFlqMly8vJqVXNQ2QmTQSUG0hD/rlKjevBTePJ4aeDQpRbyj j65v1CH5QgdcPDFsPy6+6Jv97zFNPrh7pmmCb8RsaDg95BYCVH8LHGKgChA/YKjeBdeh iAJIX0wZQygkasQ4fsGxtgIWuGuvjFNA53CW1MfiUuErrKnUVdLYbHUemAkdoXdwfEpc QXjaEM25MYgL1MMuTL+CT1Y7/ELQG/8W+XoJM7BmdmdMM/hIpDPmDODHl0yz+nGjW70R Clcw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1763167617; x=1763772417; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Mr/52DwIA8Vew8AuO0L8R6bm0vR8dQ+5A9WA+WG6t/s=; b=UTZVqr7Dh5Y48D3GFiwj5SCCvX2u6WXRutE+67e0q6wu++rTT5Am0RDH/1OyMMFk/r /7tSXyNk22DjKJ+tARZv1cgB9tG52xCIhiIAsb61BO8GyiNx9p/FQKZlbtW5sNKc47QV 2oPskhdyzDkQYlhpAo/kSTmThO0ITBNMNIT7V617R979bATZWPnqjoFD+rB5qk6Gwfee cgGR8XJqlrqXVc3r0gWkFUfavavHuAmz6QjFd1w/dBKoIML+XMFJL9jBCBxue+aavAXg oJMOBuDYpzOo2BtXifsBZ/FX7E8oUhbgfyWKU0aqM9JRzXgISEXuAR/Hz9beULivL3Xk 95bw== X-Forwarded-Encrypted: i=1; AJvYcCVDLFKXymu3T4CS4ttISiSFSUflOUEgUsz8LBNW+ph8diHQ4bJGuA7nBEl4SkMvgp0//sFuwDulMg==@kvack.org X-Gm-Message-State: AOJu0YwlK3ISeggYDFt3nkGUQMaJq/wYulxA0rACzot2QII/HEI48Hvg 8VjJcnWO8TJ9iOesrXb8DrGIpC7eYg9zOZ1BKnMH8d7MLAuNW/NlNuQazST7x26C5OTong9GzZv O2ylJnsgYfAloJW9zeY2AnPHGPQ== X-Google-Smtp-Source: AGHT+IHPDsoGUhVWbmh0UerKKIaGr6kr4KuHT3qBmIvhj2MnXtnNCORQphwRQGqEcjJQnhvfFDaRm0g88w6S7pk3mw== X-Received: from pjbdb8.prod.google.com ([2002:a17:90a:d648:b0:343:5c2:dd74]) (user=ackerleytng job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:1dc9:b0:340:29a1:1b0c with SMTP id 98e67ed59e1d1-343f9e93781mr5917746a91.7.1763167617416; Fri, 14 Nov 2025 16:46:57 -0800 (PST) Date: Fri, 14 Nov 2025 16:46:56 -0800 In-Reply-To: Mime-Version: 1.0 References: <5a4dfc265a46959953e6c24730d22584972b1179.1760731772.git.ackerleytng@google.com> Message-ID: Subject: Re: [RFC PATCH v1 11/37] KVM: guest_memfd: Add support for KVM_SET_MEMORY_ATTRIBUTES From: Ackerley Tng To: Yan Zhao Cc: cgroups@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, x86@kernel.org, akpm@linux-foundation.org, binbin.wu@linux.intel.com, bp@alien8.de, brauner@kernel.org, chao.p.peng@intel.com, chenhuacai@kernel.org, corbet@lwn.net, dave.hansen@intel.com, dave.hansen@linux.intel.com, david@redhat.com, dmatlack@google.com, erdemaktas@google.com, fan.du@intel.com, fvdl@google.com, haibo1.xu@intel.com, hannes@cmpxchg.org, hch@infradead.org, hpa@zytor.com, hughd@google.com, ira.weiny@intel.com, isaku.yamahata@intel.com, jack@suse.cz, james.morse@arm.com, jarkko@kernel.org, jgg@ziepe.ca, jgowans@amazon.com, jhubbard@nvidia.com, jroedel@suse.de, jthoughton@google.com, jun.miao@intel.com, kai.huang@intel.com, keirf@google.com, kent.overstreet@linux.dev, liam.merwick@oracle.com, maciej.wieczor-retman@intel.com, mail@maciej.szmigiero.name, maobibo@loongson.cn, mathieu.desnoyers@efficios.com, maz@kernel.org, mhiramat@kernel.org, mhocko@kernel.org, mic@digikod.net, michael.roth@amd.com, mingo@redhat.com, mlevitsk@redhat.com, mpe@ellerman.id.au, muchun.song@linux.dev, nikunj@amd.com, nsaenz@amazon.es, oliver.upton@linux.dev, palmer@dabbelt.com, pankaj.gupta@amd.com, paul.walmsley@sifive.com, pbonzini@redhat.com, peterx@redhat.com, pgonda@google.com, prsampat@amd.com, pvorel@suse.cz, qperret@google.com, richard.weiyang@gmail.com, rick.p.edgecombe@intel.com, rientjes@google.com, rostedt@goodmis.org, roypat@amazon.co.uk, rppt@kernel.org, seanjc@google.com, shakeel.butt@linux.dev, shuah@kernel.org, steven.price@arm.com, steven.sistare@oracle.com, suzuki.poulose@arm.com, tabba@google.com, tglx@linutronix.de, thomas.lendacky@amd.com, vannapurve@google.com, vbabka@suse.cz, viro@zeniv.linux.org.uk, vkuznets@redhat.com, wei.w.wang@intel.com, will@kernel.org, willy@infradead.org, wyihan@google.com, xiaoyao.li@intel.com, yilun.xu@intel.com, yuzenghui@huawei.com, zhiquan1.li@intel.com Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: mrjn4uutt5wyefqt5utgk7uwibhxadup X-Rspam-User: X-Rspamd-Queue-Id: D7B40C000A X-Rspamd-Server: rspam01 X-HE-Tag: 1763167618-165821 X-HE-Meta: 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 VmH+LfyP 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 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: List-Subscribe: List-Unsubscribe: Yan Zhao writes: > On Fri, Oct 17, 2025 at 01:11:52PM -0700, Ackerley Tng wrote: >> For shared to private conversions, if refcounts on any of the folios >> within the range are elevated, fail the conversion with -EAGAIN. >> >> At the point of shared to private conversion, all folios in range are >> also unmapped. The filemap_invalidate_lock() is held, so no faulting >> can occur. Hence, from that point on, only transient refcounts can be >> taken on the folios associated with that guest_memfd. >> >> Hence, it is safe to do the conversion from shared to private. >> >> After conversion is complete, refcounts may become elevated, but that >> is fine since users of transient refcounts don't actually access >> memory. >> >> For private to shared conversions, there are no refcount checks. any >> transient refcounts are expected to drop their refcounts soon. The >> conversion process will spin waiting for these transient refcounts to >> go away. > Where's the code to spin? > Thanks, I will fix the commit message for the next revision. >> +/* >> + * Preallocate memory for attributes to be stored on a maple tree, pointed to >> + * by mas. Adjacent ranges with attributes identical to the new attributes >> + * will be merged. Also sets mas's bounds up for storing attributes. >> + * >> + * This maintains the invariant that ranges with the same attributes will >> + * always be merged. >> + */ >> +static int kvm_gmem_mas_preallocate(struct ma_state *mas, u64 attributes, >> + pgoff_t start, size_t nr_pages) >> +{ >> + pgoff_t end = start + nr_pages; >> + pgoff_t last = end - 1; >> + void *entry; >> + >> + /* Try extending range. entry is NULL on overflow/wrap-around. */ >> + mas_set_range(mas, end, end); >> + entry = mas_find(mas, end); >> + if (entry && xa_to_value(entry) == attributes) >> + last = mas->last; >> + >> + mas_set_range(mas, start - 1, start - 1); > Check start == 0 ? > Thanks! >> + entry = mas_find(mas, start - 1); >> + if (entry && xa_to_value(entry) == attributes) >> + start = mas->index; >> + >> + mas_set_range(mas, start, last); >> + return mas_preallocate(mas, xa_mk_value(attributes), GFP_KERNEL); >> +} > ... > >> +static long kvm_gmem_set_attributes(struct file *file, void __user *argp) >> +{ >> + struct gmem_file *f = file->private_data; >> + struct inode *inode = file_inode(file); >> + struct kvm_memory_attributes2 attrs; >> + pgoff_t err_index; >> + size_t nr_pages; >> + pgoff_t index; >> + int r; >> + >> + if (copy_from_user(&attrs, argp, sizeof(attrs))) >> + return -EFAULT; >> + >> + if (attrs.flags) >> + return -EINVAL; >> + if (attrs.attributes & ~kvm_supported_mem_attributes(f->kvm)) >> + return -EINVAL; >> + if (attrs.size == 0 || attrs.offset + attrs.size < attrs.offset) >> + return -EINVAL; >> + if (!PAGE_ALIGNED(attrs.offset) || !PAGE_ALIGNED(attrs.offset)) > Should be > if (!PAGE_ALIGNED(attrs.offset) || !PAGE_ALIGNED(attrs.size)) > ? > Thanks! >> + return -EINVAL; >> + >> + if (attrs.offset > inode->i_size || > Should be > if (attrs.offset >= inode->i_size || > ? Thanks! >> + attrs.offset + attrs.size > inode->i_size) >> + return -EINVAL; >> + >> + nr_pages = attrs.size >> PAGE_SHIFT; >> + index = attrs.offset >> PAGE_SHIFT; >> + r = __kvm_gmem_set_attributes(inode, index, nr_pages, attrs.attributes, >> + &err_index); >> + if (r) { >> + attrs.error_offset = err_index << PAGE_SHIFT; >> + >> + if (copy_to_user(argp, &attrs, sizeof(attrs))) >> + return -EFAULT; >> + } >> + >> + return r; >> +}