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 3E293C5B572 for ; Wed, 12 Aug 2026 16:07:30 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id EA1BE6B0143; Wed, 12 Aug 2026 12:07:28 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E53126B0146; Wed, 12 Aug 2026 12:07:28 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D41DA6B0148; Wed, 12 Aug 2026 12:07:28 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id AA2F76B0143 for ; Wed, 12 Aug 2026 12:07:28 -0400 (EDT) Received: from smtpin06.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 40A39803FB for ; Wed, 12 Aug 2026 16:07:28 +0000 (UTC) X-FDA: 85093097376.06.A38180F Received: from mail-pf1-f199.google.com (mail-pf1-f199.google.com [209.85.210.199]) by imf31.hostedemail.com (Postfix) with ESMTP id 76DEE2000E for ; Wed, 12 Aug 2026 16:07:26 +0000 (UTC) Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=google.com header.s=20251104 header.b=UO1PGqdR; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf31.hostedemail.com: domain of 3PJp8agYKCL0vhdqmfjrrjoh.frpolqx0-ppnydfn.ruj@flex--seanjc.bounces.google.com designates 209.85.210.199 as permitted sender) smtp.mailfrom=3PJp8agYKCL0vhdqmfjrrjoh.frpolqx0-ppnydfn.ruj@flex--seanjc.bounces.google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1786550846; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=qhGw4WaAvR2D6BZq/c2SGM6eMLuDwIODKQW5IVkvny8=; b=NTW/PvPUs0RKlo29vveAyYQIpuwQI5V2uJHwZnv/H9rmZ8AosUubBM4+PyzE3j8Ac6CRX7 u9U842Y5+QdKSYzvyVZbGlUoRtyYLYD4lPFxNyh/Pz0Bo5yTOjd1TsA/xvqu+BunwzzGJX /NXKfRnhXktCPoQ4iCRRga+lNjaDnLA= ARC-Authentication-Results: i=1; imf31.hostedemail.com; dkim=pass header.d=google.com header.s=20251104 header.b=UO1PGqdR; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf31.hostedemail.com: domain of 3PJp8agYKCL0vhdqmfjrrjoh.frpolqx0-ppnydfn.ruj@flex--seanjc.bounces.google.com designates 209.85.210.199 as permitted sender) smtp.mailfrom=3PJp8agYKCL0vhdqmfjrrjoh.frpolqx0-ppnydfn.ruj@flex--seanjc.bounces.google.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1786550846; b=10XWDSG5ZbAU53Yj90Jk8JfBkL1jqJSQJCY3w5cSc2gbVh8TEr0dATNuPZ4P1TkVLafW11 +0oXIlwAnB6xXDgMqYksqfdJK8qSxPYChoD7xQYddwcPLb37nvAmPQmqM71D3nWbwCPpao T0cfBS9hdDBwlO0ktlN5TN4dA3JGB/0= Received: by mail-pf1-f199.google.com with SMTP id d2e1a72fcca58-848544a8496so1333377b3a.0 for ; Wed, 12 Aug 2026 09:07:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1786550845; x=1787155645; darn=kvack.org; h=content-transfer-encoding:content-type:cc:to:from:subject :message-id:references:mime-version:in-reply-to:date:from:to:cc :subject:date:message-id:reply-to:content-type; bh=qhGw4WaAvR2D6BZq/c2SGM6eMLuDwIODKQW5IVkvny8=; b=UO1PGqdRsBFGsFa6pX0tqzgWh41Q6BQAlFMQdFe3l9VwO+k+J889XXTJdgOclNvYf1 OgnXcQ8ExWiomOF1yO5FS1CefAT5AwrxX31eiKwSC7Md4PgkhqoMkZpAOGHDnvuXhxo2 0+Ss+VzDAVJ+SwU5zHKIB68pctEJY+WQjVfnmM6+UQWWuuhqeZmqWOkTEH/4/Ga0fHrN OaOc/Uuj2f0VWw6hABFTPWRezEzARGqoNInD/jsNuyi57Z4uKqDvhBWcfSaPOoxVO8xV uTOmM0JUVU82Pj3W7xu7jQcA8Q1Nzd3M0sXDIsQZormUxhH7kZUr74inx/D4ba5cUFGq 8VlA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786550845; x=1787155645; h=content-transfer-encoding:content-type: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 :content-type; bh=qhGw4WaAvR2D6BZq/c2SGM6eMLuDwIODKQW5IVkvny8=; b=jWcoh6ybQHExDmzKcuX49eF5Li3NqqUehtyr84nFQKhm0femB30H6w4Ba4KBxQVsWK DS94bwySG/xz2HRS0KOwtRoQUohIK4P6cmvWraxdjyV5rAB+u6cSWYUSXyoiKL7BTNM9 N+ILPYxPRqe61yBpfLRSahGp+x6c01GekK0B1kzSWHMTus5lM0cAEIgsQFMt98rvZCxH GxHFcUPi6CHpG8pZlwppXa7PUK72r6xRSnCVsQHm7PdZBnpFl+xrIcSPL9kfmWIYaeEx QTY6r5FTaG80VjZc50z34gkNtmDEcCxH9nZv+R//JxSNoO7tgSzcCiDXjMM8sgC+5LHs e/dA== X-Forwarded-Encrypted: i=1; AHgh+RrvFUDy3oVt7uiAnJB+FVP44b4wRKI/Ck3cNy8ZoUISx/ieT2lFROLrcvtNrcbxewmjJlnT8u/kNw==@kvack.org X-Gm-Message-State: AOJu0YxQwMEXhHAaLqYG+JYX4KrqJyFKHwsW4vbOBywhsLhrS4kRUqRk JxbGgU8SbhB5Bw8xtfvztgtD2s0MblmN+aY3fY18I4qQ00A3o56DV4gNTqa/u9uvz2o6miN9wl5 ecFhdJg== X-Received: from pfiu19.prod.google.com ([2002:a05:6a00:1253:b0:84e:5c66:796c]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:1311:b0:847:9c3a:b77f with SMTP id d2e1a72fcca58-84fb55806bamr5778881b3a.35.1786550844921; Wed, 12 Aug 2026 09:07:24 -0700 (PDT) Date: Wed, 12 Aug 2026 09:07:24 -0700 In-Reply-To: <824a27d101d5b2e2a8a53fb81f5e4ecf15140a1f.camel@infradead.org> Mime-Version: 1.0 References: <20260811162423.GL544626@ziepe.ca> <20260811172627.GN544626@ziepe.ca> <20260811181915.GO544626@ziepe.ca> <27f2326dc66d6341174c0e510aa518a1297b66ae.camel@infradead.org> <824a27d101d5b2e2a8a53fb81f5e4ecf15140a1f.camel@infradead.org> Message-ID: Subject: Re: [PATCH] mm/mmu_notifier: Remove non_block_start/end() from notifier invocation From: Sean Christopherson To: David Woodhouse Cc: Fred Griffoul , Paolo Bonzini , Jason Gunthorpe , akpm@linux-foundation.org, david@kernel.org, mhocko@suse.com, rostedt@goodmis.org, bigeasy@linutronix.de, simona.vetter@ffwll.ch, jglisse@redhat.com, christian.koenig@amd.com, paulmck@kernel.org, linux-mm@kvack.org, kvm@vger.kernel.org, linux-rt-devel@lists.linux.dev, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Stat-Signature: 3jhix3w156e6n9wd4msz6zpx458aw1zp X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 76DEE2000E X-HE-Tag: 1786550846-495191 X-HE-Meta: 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 QrLM7roF 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Aug 12, 2026, David Woodhouse wrote: > On Tue, 2026-08-11 at 15:58 -0700, Sean Christopherson wrote: > > On Tue, Aug 11, 2026, David Woodhouse wrote: > > > On Tue, 2026-08-11 at 22:21 +0200, Paolo Bonzini wrote: > > > >=20 > > > > for_each_present_cpu(cpu) > > > > =C2=A0=C2=A0=C2=A0 if (per_cpu(kvm_gpc_reader, cpu) =3D=3D gpc) > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 cpumask_set_cpu(cpu, gpc= _readers); > > > > __kvm_kick_many_cpus(cpus, wait); > > >=20 > > >=20 > > > I'm literally sitting here watching you reinvent what SRCU already do= es. > >=20 > > The problem, for me at least, is that SRCU does this and a _lot_ more. > >=20 > > > Which, again, is *fine* given the behaviour of *these* read-side sect= ions. > >=20 > > Well, yeah.=C2=A0 Why use a nailgun to put a nail into the wall to hang= a picture > > frame? (other than the indisputable fact that power tools are fun).=C2= =A0 >=20 > It's not a nailgun, it's a drill. And in this analogy, my observation > that it works absolutely fine for us with *these* SRCU read-side users > ... is equivalent to finding the torque setting that lets you put it > into screwdriver mode. Yeah, but my concern is that there are KVM users out there that will put th= e drill into hammer drill mode, likely unknowingly, and then complain that "w= e" put a hole in their wall. What I want is a strong guarantee that the user can't configure bad torque/= mode settings, even unintentionally.