From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 7BD4654768; Fri, 1 May 2026 02:11:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777601477; cv=none; b=jYmT8H9SKmAbvXdZbivEmwd2R60j3D+8iQATJgsyCaZCrfyCcDp5N3AzgN3SsIPaswpdR+OjdpA5AIf4Ju7z0jHok8uTXvCnRiVMZoMkdx6lqE05DXaaJAbt+ZY33PHClf5TKOYNI86dLwOkw59UCyF5J4uwcTiBv2BHNICOEuY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777601477; c=relaxed/simple; bh=9QR0cnUgXF6rP+G/fgL1ZOPWMm8v63S58EfEC1IYVzQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OHEWWJGvM5+6YcI/22U2P26dQfVWruzteqmNgT/tOabSX8XnN5BpyjYfMA5FUnnPNfA5rGZu8txwnrHJ83Eg95Sm7Xc4HjLSNq7dw9C06s+YlENuzPoUqXKnho9eVFtFFf/bf56HC7eLmk/+/rJqFPesIC9iVjFZ3T6FE6AXMOc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=uRa3t4sD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="uRa3t4sD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EA878C2BCB3; Fri, 1 May 2026 02:11:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777601477; bh=9QR0cnUgXF6rP+G/fgL1ZOPWMm8v63S58EfEC1IYVzQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=uRa3t4sDDbQpv7M6lTSaoochov6MAYzb6y7riWmPgQGz26Fxvq1g0V6HxcEVB4OOZ dDm6eFhIZRdVv31oRZYaYzcM7dzco1gJXHNAbV9z2w6ENGowfGEpvZjgqb+1Ow3lsx 9gYSbxshRf5euC1t6Eq4JDevvKjmwWKRicLObAiTsLAHsFzXK7MlcdnWyBzJwVVYBM OXGarWvtRJ0/zcrnZPCMdqlgy6S/nsKNYM2bX5T6wASoFB/USX7PPs2/5lDpaeNa5f sIQhDVq9nGKrvIyg/x9pS/ik1r8n0Pn28IWUnGTQvJqAD8FFrt8N5nUDZyBahPQGnu zC9DTSnlxWZGA== Received: by finisterre.sirena.org.uk (Postfix, from userid 1000) id 94D0A1AC5863; Fri, 01 May 2026 03:11:14 +0100 (BST) Date: Fri, 1 May 2026 11:11:14 +0900 From: Mark Brown To: Marc Zyngier Cc: Leonardo Bras , Catalin Marinas , Will Deacon , Oliver Upton , Joey Gouly , Suzuki K Poulose , Zenghui Yu , "Rafael J. Wysocki" , Len Brown , Saket Dumbre , Paolo Bonzini , Chengwen Feng , Jonathan Cameron , Kees Cook , =?utf-8?Q?Miko=C5=82aj?= Lenczewski , Ryan Roberts , Yang Shi , Thomas Huth , mrigendrachaubey , Yeoreum Yun , Kevin Brodsky , James Clark , Ard Biesheuvel , Fuad Tabba , Raghavendra Rao Ananta , Nathan Chancellor , Vincent Donnefort , Lorenzo Pieralisi , Sascha Bischoff , Anshuman Khandual , Tian Zheng , Wei-Lin Chang , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-acpi@vger.kernel.org, acpica-devel@lists.linux.dev, kvm@vger.kernel.org Subject: Re: [PATCH v1 00/12] KVM Dirty-bit cleaning accelerator (HACDBS) Message-ID: References: <20260430111424.3479613-2-leo.bras@arm.com> <86bjf0zj2p.wl-maz@kernel.org> <86a4ukzel3.wl-maz@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="ssT59TgwkbIJmTw+" Content-Disposition: inline In-Reply-To: <86a4ukzel3.wl-maz@kernel.org> X-Cookie: 667: --ssT59TgwkbIJmTw+ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Apr 30, 2026 at 03:51:20PM +0100, Marc Zyngier wrote: > Leonardo Bras wrote: > > There is no enablement needed on VMM side. > > Yes, I have created a VM on upstream qemu with --enable-kvm and migrate= d it=20 > > on the same host. (Inside a model) > > That was the first test I used, but then I found out that kvm selftests= =20 > > stress up multiple scenarios in an easier way. > Except when they don't. In my experience, the selftests are only there > to give the CI people the fuzzy feeling that they are doing something > useful. I have a collection of examples indicating that what these > things test is not representative of the bugs we have in KVM. There's a bit of a circular thing there - if things are working well then the selftests really shouldn't be representitive of the problems that turn up since people ought to have seen any issues they show during development. If you could share your list that'd be helpful. TBH the various stress style tests like the dirty bit ones in the KVM selftests are actually a bit of a pain for CI IME. Since they all control their runtimes by iteration counts rather than time there's scaling issues, the performance is such that on lower end systems they're often on the edge of generating timeouts leading to unstable results. They also interact so poorly with the fast models that the run time blows up spectacularly which is it's own problem trying to run them, that's partly on the model side of course. These performance and/or stress tests really aren't idiomatic for kselftest so there's always going to be some tension with trying to run them in that framework. --ssT59TgwkbIJmTw+ Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmn0C8EACgkQJNaLcl1U h9CS4gf6A7/M0j4C+bjIv3MUjhE/mp8ttmFweM6NFGjW71XsY5UMxrlSOLPo8FsA dc18jjcaPaGl6ozZGbZnEdt4/olC2ZeZCW+itSIOMNCTlcUpK7MRkAu6/L0/NRyF hUup3657nGbemC0awUnJgdPtnRl2cUej+eLw6rLa6LUpC2VNQixM1GputtDlcbMB xtTncUwiuypXtPjVfGwx6NasjoOux+XHXF3s2tdeFX8crXdtFojI6aGqNZ0+abxH RT/GD1WIOVZwmAQ0PYhC8XkPYyL8wQ92yjVZGjw5vXDPNlS/CesakgrnLJcL5pfq wxdoTRitTAuP8hoREPUgw/vN5C7QQA== =FWnL -----END PGP SIGNATURE----- --ssT59TgwkbIJmTw+--