From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 05379270551 for ; Tue, 23 Sep 2025 17:05:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758647158; cv=none; b=RO1Jfesxek910hDmPmb1XKXJnZD3yI5S7HhcJfP0/nev+hFRN5FhvgiNKe2LoXcLVECBSXwUNwcN0+vgMmm3stCWLmgq6D7qyejy/YoywOo6c8AEZBX2BuoRPPg7oWLGGIJHf09knBw/mv4sUYQ8VSrdemcK+7G70FPWLCBzKMM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758647158; c=relaxed/simple; bh=Si+gRDqfMlxuN0KqN3KFYYBkczK7pbhlc1HLNzDjYGg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ed3zpWPayXWIBpr1fxGwWEbgrddFGbH+rl0S0tzICGBVuuy/fwm6DErUJSxndW4DHn1IRhzStD+l4T+M7p7RimZd5eoAU4bYby1/Rg1dhNbiDvuA2Xor4ZIU3Sj7LiVYvZENrtYVg+OH+5y41nk9yDDDj126IvO1vLrAKwY1EBs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=DnXjNFVw; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="DnXjNFVw" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1758647155; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Si+gRDqfMlxuN0KqN3KFYYBkczK7pbhlc1HLNzDjYGg=; b=DnXjNFVwpzCm6XH0AOVNqDfBPmiyHV3ljem5nk9UqOse3WyhhQdhx9inDJ/NYrvDIfHlkr iYTcVW5kuNVjJVSNfyCaenJfGqI3H0NZniIgMAjEEmfCgUm8JZOvD5woGdBK0Co2QGTzIf A7qzrbcqXLh5Vil121x+PaEaP0xDFD8= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-456-r0ZRWA2iMGiiOTICcbLMBg-1; Tue, 23 Sep 2025 13:05:50 -0400 X-MC-Unique: r0ZRWA2iMGiiOTICcbLMBg-1 X-Mimecast-MFC-AGG-ID: r0ZRWA2iMGiiOTICcbLMBg_1758647148 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C7C0D1800372; Tue, 23 Sep 2025 17:05:47 +0000 (UTC) Received: from localhost (unknown [10.2.17.69]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id B878D19560B1; Tue, 23 Sep 2025 17:05:46 +0000 (UTC) Date: Tue, 23 Sep 2025 13:05:45 -0400 From: Stefan Hajnoczi To: Cong Wang Cc: linux-kernel@vger.kernel.org, pasha.tatashin@soleen.com, Cong Wang , Andrew Morton , Baoquan He , Alexander Graf , Mike Rapoport , Changyuan Lyu , kexec@lists.infradead.org, linux-mm@kvack.org, multikernel@lists.linux.dev Subject: Re: [RFC Patch 0/7] kernel: Introduce multikernel architecture support Message-ID: <20250923170545.GA509965@fedora> References: <20250918222607.186488-1-xiyou.wangcong@gmail.com> <20250919212650.GA275426@fedora> <20250922142831.GA351870@fedora> 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="fOWoD/rtAfxeWV+w" Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 --fOWoD/rtAfxeWV+w Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Sep 22, 2025 at 03:41:18PM -0700, Cong Wang wrote: > On Mon, Sep 22, 2025 at 7:28=E2=80=AFAM Stefan Hajnoczi wrote: > > > > On Sat, Sep 20, 2025 at 02:40:18PM -0700, Cong Wang wrote: > > > On Fri, Sep 19, 2025 at 2:27=E2=80=AFPM Stefan Hajnoczi wrote: > > > > > > > > On Thu, Sep 18, 2025 at 03:25:59PM -0700, Cong Wang wrote: > > > > > This patch series introduces multikernel architecture support, en= abling > > > > > multiple independent kernel instances to coexist and communicate = on a > > > > > single physical machine. Each kernel instance can run on dedicate= d CPU > > > > > cores while sharing the underlying hardware resources. > > > > > > > > > > The multikernel architecture provides several key benefits: > > > > > - Improved fault isolation between different workloads > > > > > - Enhanced security through kernel-level separation > > > > > > > > What level of isolation does this patch series provide? What stops > > > > kernel A from accessing kernel B's memory pages, sending interrupts= to > > > > its CPUs, etc? > > > > > > It is kernel-enforced isolation, therefore, the trust model here is s= till > > > based on kernel. Hence, a malicious kernel would be able to disrupt, > > > as you described. With memory encryption and IPI filtering, I think > > > that is solvable. > > > > I think solving this is key to the architecture, at least if fault > > isolation and security are goals. A cooperative architecture where > > nothing prevents kernels from interfering with each other simply doesn't > > offer fault isolation or security. >=20 > Kernel and kernel modules can be signed today, kexec also supports > kernel signing via kexec_file_load(). It migrates at least untrusted > kernels, although kernels can be still exploited via 0-day. Kernel signing also doesn't protect against bugs in one kernel interfering with another kernel. > > > > On CPU architectures that offer additional privilege modes it may be > > possible to run a supervisor on every CPU to restrict access to > > resources in the spawned kernel. Kernels would need to be modified to > > call into the supervisor instead of accessing certain resources > > directly. > > > > IOMMU and interrupt remapping control would need to be performed by the > > supervisor to prevent spawned kernels from affecting each other. >=20 > That's right, security vs performance. A lot of times we have to balance > between these two. This is why Kata Container today runs a container > inside a VM. >=20 > This largely depends on what users could compromise, there is no single > right answer here. >=20 > For example, in a fully-controlled private cloud, security exploits are > probably not even a concern. Sacrificing performance for a non-concern > is not reasonable. >=20 > > > > This seems to be the price of fault isolation and security. It ends up > > looking similar to a hypervisor, but maybe it wouldn't need to use > > virtualization extensions, depending on the capabilities of the CPU > > architecture. >=20 > Two more points: >=20 > 1) Security lockdown. Security lockdown transforms multikernel from > "0-day means total compromise" to "0-day means single workload > compromise with rapid recovery." This is still a significant improvement > over containers where a single kernel 0-day compromises everything > simultaneously. I don't follow. My understanding is that multikernel currently does not prevent spawned kernels from affecting each other, so a kernel 0-day in multikernel still compromises everything? >=20 > 2) Rapid kernel updates: A more practical way to eliminate 0-day > exploits is to update kernel more frequently, today the major blocker > is the downtime required by kernel reboot, which is what multikernel > aims to resolve. If kernel upgrades are the main use case for multikernel, then I guess isolation is not necessary. Two kernels would only run side-by-side for a limited period of time and they would have access to the same workloads. Stefan >=20 > I hope this helps. >=20 > Regards, > Cong Wang >=20 --fOWoD/rtAfxeWV+w Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmjS02kACgkQnKSrs4Gr c8gaLgf+LttcrIImZ/l3um6RUl/4dYace1hoDwxQJPCPksRImb0wzZW4C3r/6W8V dssJAEtVxaLcMnKlkA+usUipzCoHQqjOD6IVOe3gxnD28sSaIuE8v+RhftRbEMNI ytTI1l4AHyPwWr2nQG+FQZm2hf7LQUd2uItfnOjIS/sSelm7eOHr1m8zXvYDy1zT JXKNxZCk0PGTkYHCDZkmnZotwC/OEUD4htrk2s1V+xaGhXx8VS59XNacaileaplO rRPGU2lU6vXA/TRhs+FvZqPGFj0gffZrc+5H/pHCPVeod8Drolcf0YO+9WQ+b+n5 SLcZ7lhWe6O/QynTmIpd89aXu+L0tA== =KKCS -----END PGP SIGNATURE----- --fOWoD/rtAfxeWV+w--