From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f200.google.com (mail-pf1-f200.google.com [209.85.210.200]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 23531274B46 for ; Wed, 12 Aug 2026 16:07:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.200 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786550847; cv=none; b=GXgWmeuwyJEkefrVLmmy2oF6qGbFzld7CMUSlHsylcQL7JTWrR36e1Ecj6Ih1owlqrPUEQjtbJASLd7zEcbG2CDRcMib1gAyE5D78Wb7l3E4mJKpEDVSHh917axZ4fJITp9+5uZzwe93pTTgiboHNcwod2BX6lghq1jamW+AEtI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786550847; c=relaxed/simple; bh=qhGw4WaAvR2D6BZq/c2SGM6eMLuDwIODKQW5IVkvny8=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=sz1Hs1Bvan8ZPR3jSm0dLY4fAAr1legcU6bjbhH7o1/AH6MUaxCpSdsiiVCMtSACJsp/6WNVQVr25E/NfbKALsrvc/cWy9andJhAsgElBpxZlVjsCW4ZSMmFdc8M4wC6qaavM0n/lMIYE/XpEWL8V1XjLs01Z4eFWpVa3NLINY4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=AsjY7yph; arc=none smtp.client-ip=209.85.210.200 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="AsjY7yph" Received: by mail-pf1-f200.google.com with SMTP id d2e1a72fcca58-8484f26852dso1244133b3a.1 for ; Wed, 12 Aug 2026 09:07:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1786550845; x=1787155645; darn=vger.kernel.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=AsjY7yphxaz7CsR3aAusLXJhUo5WKPYcNfcuuPQcmLBxADJohlA0qP2c65hBZgva9s Hl9i/qdD3Xi1MMvbcv/MisLUs0IKheFHfN8WhAK/FQk4Z/yFXb3ZIvjA+d/2TlF0qqRJ IMbjfX3HJH8KHSzi+A3PCVrosCw7d1MHhAcTbU3nCE8jB3zzSG26X8F7ATCKfLS9FeU3 MJtsEEkFLfGWW2ITgGPY75Ol7yy2VRgi+xGRh/eVjLPxP7zLFSt7yK6X0oseYMsQvHjc qqP1ChzrGg1W+BI6sJtS10prr48aTiIiju7BbScLbNSSMMlhnhnwzMv+yoS76ymK3Tbq lJyQ== 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=GPwX4DPMz52EdHYLNnSl5hjB2pQVUY/P5VJEAXG0jDSxSpCUbebsSGN/p+NwoAGczq 4/zURn8ZpO/AweWUKg1jZWcVtVsutguNvW2cm/nQL+LnxTIPc3HhW7uzBYb9jjMJr5Da vY0hPCf7NIJ+HxmyvlnW89IaO5vA3Ssw5oICbAaUpz25ZuZEt6lYApdPBY77+5vRNnq5 k89pFX3a8/MxzZlU0+zzybAEPpEpqqEAWrdIItuGvB4rSl9aFVS/i2IrAXTcMOM5rfn0 7anpfyBGEM02ysyroGckHPSxx1ChomBfP2iTaM0d1oweHnxdvlAhhXCcNB6Bf49EMbgT l/EA== X-Forwarded-Encrypted: i=1; AHgh+Rpgxd/JVXflGKdif1oS6iHTiI0VH1N0lYhrcfIYEcxLMLz19OZ1r7vNci0FBZ5UQkA5N6qua4T8oXmv/5k=@vger.kernel.org X-Gm-Message-State: AOJu0YzQbJQ3BLxv0pfFNUSWJjkYf/DmnNg+JkeT6miwPI5mDbX/bH// Nxvw67b9yti3JE6rSDc/2qX7ewdZQYBlAPgIRHCP0Vz7Ps0XfGSqcPvbrkAwWTmvPw75JJDRAEF wIieseQ== 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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.