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 74921C3ABB6 for ; Mon, 5 May 2025 23:18:03 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 537EA6B0083; Mon, 5 May 2025 19:18:02 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4E6516B0085; Mon, 5 May 2025 19:18:02 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3864E6B0088; Mon, 5 May 2025 19:18:02 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 1722B6B0083 for ; Mon, 5 May 2025 19:18:02 -0400 (EDT) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 48CC5160D02 for ; Mon, 5 May 2025 23:18:02 +0000 (UTC) X-FDA: 83410419204.30.2D3EDF1 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) by imf16.hostedemail.com (Postfix) with ESMTP id 80BF6180004 for ; Mon, 5 May 2025 23:18:00 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=qzN05G6e; spf=pass (imf16.hostedemail.com: domain of 3J0cZaAYKCGISEANJCGOOGLE.COMLINUX-MMKVACK.ORG@flex--seanjc.bounces.google.com designates 209.85.214.201 as permitted sender) smtp.mailfrom=3J0cZaAYKCGISEANJCGOOGLE.COMLINUX-MMKVACK.ORG@flex--seanjc.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=1746487080; 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=Tp3hEaccs5KLjus+u7lZyGvplQzD1hJyVDYNNOcIobc=; b=lp+18AZV+cj72QYKIk8/1wHt8c7N5joZRsrVhQ/oZ8skM8TdRir/jRKNRWvrYdiGXQNho2 5EzBExa33UAgrqagTVkt5gKDNcSSCvl9yTnnKvgv3gEZw8yTJc3scRMI+UkrKxhXe5USYp XpfKAAKP0GxkZDqeOqvX28lT6m9QKgs= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=qzN05G6e; spf=pass (imf16.hostedemail.com: domain of 3J0cZaAYKCGISEANJCGOOGLE.COMLINUX-MMKVACK.ORG@flex--seanjc.bounces.google.com designates 209.85.214.201 as permitted sender) smtp.mailfrom=3J0cZaAYKCGISEANJCGOOGLE.COMLINUX-MMKVACK.ORG@flex--seanjc.bounces.google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1746487080; a=rsa-sha256; cv=none; b=UUVHmFa7vZOCqnvJvgCCwqSMt61PKq/yRGfB6qJ0n+nmHhCIY4h6VylaVvZCv7VmO2npSJ 7igYA9YKJk1hgWU7wEv46QhMm50knUnl+IgiWRle33HEp/DKI8ZVREjylInMcdjOrcyBYw 65e7NjaNrJ4zPT+HDNe1tCAe4ZgBg04= Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-22e40e747a3so165795ad.0 for ; Mon, 05 May 2025 16:18:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1746487079; x=1747091879; 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=Tp3hEaccs5KLjus+u7lZyGvplQzD1hJyVDYNNOcIobc=; b=qzN05G6exVv00pYGJM/SInt7wPoLKsASdzJZIppN4CkjFXK3Oo/VyqGXbwK2FnFgxJ xFEvhO85ZyJHpQgPOIl63mcwn4PaGl96WQc6kFe/ObfgZL9hNLTQ87AvdFGW4XARGHo8 JzPHSGQrItDicaQJN6C0q2VrVxjhxGfJIyLJ0qSp2tX3Dm6Zpu8+U+sPS8iudcLswy8q Db447Q8jk1z5F5kbjt1gIB+Vh8TJ1N7zOW+WJfPUn2zkvGDFeaBkwJfGetuY3DLkY7+6 lAH6RWKZch6Xrr7Xe8s+5wnFTH8WvqRDhPXN3zIheBIsVVcJW27qI5LCD5MOe4w3yovJ uvdQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1746487079; x=1747091879; 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=Tp3hEaccs5KLjus+u7lZyGvplQzD1hJyVDYNNOcIobc=; b=sPDVmXqUlofnOLYcoNqBCtRLy+xSy0fkFDqp8XV8FwQIeE52AQ5bIWJQLvGqOxmE9T bsz9MuwvfYYpC/9le0VkJdNv17Z/qXzYWvJCc4g0GA7LI30HJlNO7bqDVXf/y2PmIuVA wu3NiVRWZKjc50txv/bfolmUjfKTknGqj/exBuoKx1DZaUQp1v+uUbf0t/E+QuQVmNOy MVMeV+9E3eOd8N26XGSMJOxScKuE5E5ACLqIARqxk8PP5ky75X5sG4d5cg50xdHsWQYx 5ZMWQjOOaFziqooaUrdLykMtrTMjzxLnaxZ1wGnDR2zcw2Y/+W50RKyGgN53XHqr0kbw 5sBA== X-Forwarded-Encrypted: i=1; AJvYcCV+ufZUVsfrDaRlHEPkMw+pTk1TlkmgTq4A1rBiB1c3TO1LkWeUHFowdHKSg+6vbthWglgx8SX/RA==@kvack.org X-Gm-Message-State: AOJu0YyrfzS1M9yHSzgS+BXdu5WMwYIpKPdgnCXzU3ODrfviP4JgBYSk Mvh/G7nVBoj7QKhb68cAwmhDermssp/6zyiJX/0KUPly1CHuRenfv6+Vv3vLnfoVQYgLc1rKzf9 5iA== X-Google-Smtp-Source: AGHT+IGhrX1MtCaIusgQgNQRAcx+0E6rNYmRwUcmQ9PrQBY1+RE7Ktib/G6MWTeo5oHjCygbMWb2/Z516S8= X-Received: from plv19.prod.google.com ([2002:a17:903:bd3:b0:220:cd24:457]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:e18b:b0:22e:39f8:61fa with SMTP id d9443c01a7336-22e39f864c8mr6120915ad.34.1746487079377; Mon, 05 May 2025 16:17:59 -0700 (PDT) Date: Mon, 5 May 2025 16:17:58 -0700 In-Reply-To: Mime-Version: 1.0 References: <386c1169-8292-43d1-846b-c50cbdc1bc65@redhat.com> <7e32aabe-c170-4cfc-99aa-f257d2a69364@redhat.com> Message-ID: Subject: Re: [PATCH v8 06/13] KVM: x86: Generalize private fault lookups to guest_memfd fault lookups From: Sean Christopherson To: Ackerley Tng Cc: David Hildenbrand , Fuad Tabba , kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, 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, 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 Content-Type: text/plain; charset="us-ascii" X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 80BF6180004 X-Stat-Signature: c9u4fc1qoce3zeqpnamq56a3an7oq6u9 X-HE-Tag: 1746487080-828163 X-HE-Meta: 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 nokpXbJ0 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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: On Mon, May 05, 2025, Ackerley Tng wrote: > > On 03.05.25 00:00, Ackerley Tng wrote: > > We want to disable large pages if (using 2M region as example) > > > > (a) Mixed memory attributes. If a PFN falls into a 2M region, and parts > > of that region are shared vs. private (mixed memory attributes -> > > KVM_LPAGE_MIXED_FLAG) > > > > -> With gmem-shared we could have mixed memory attributes, not a PFN > > fracturing. (PFNs don't depend on memory attributes) > > > > (b) page track: intercepting (mostly write) access to GFNs > > > > Could you explain more about page track case? KVM disallows hugepages when shadowing a gfn, because write-protecting a 2MiB (let alone a 1GiB) page would be insanely expensive, as KVM would need to intercept and emulate an absurd number of instructions that have nothing to do with the guest's page tables.