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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8D7F9C61DD3 for ; Wed, 2 Sep 2026 00:39:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:Cc:To:From: Subject:Message-ID:References:Mime-Version:In-Reply-To:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=FaTmFFkWvtpI1wxK9lbUH5Q49TqxcdmMs9wtskLlSB4=; b=poM4Hsqb2XvEICgsMW6tYbhfRZ 4KLfuXmZNVcP8qDLB0OnuTw5RVM7g/E8VjLWyWB9kddYjSc7t6BFELZ/s+gto4KjmvXIscYnOVIdx jAVFtrsCku8cnqAWyEcgSt0lutC2kcAALlX/fIMZ3dRGZTQhN7aTS224Z7hF5lWV1zXV1jNMHQF2N 5B1XZEkoSKyU+kNOQQvyb8SYHLwBsUfw90lQQdsCJ28vxkvlKAG1NpcigbbH2ocuW1wCQDLJOK0KC 7Qa0FZRx8Aao9VTfOyYD3NfXNOaM+Qubsp2AtSlhawVD4qdfPIDe+lxBTbHRDyi1VAkm9eQAagZuB dPxG1RNw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x1Z0E-0000000Dafs-26pX; Wed, 02 Sep 2026 00:38:58 +0000 Received: from mail-pl1-x647.google.com ([2607:f8b0:4864:20::647]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x1Z0C-0000000DafV-05NX for linux-arm-kernel@lists.infradead.org; Wed, 02 Sep 2026 00:38:57 +0000 Received: by mail-pl1-x647.google.com with SMTP id d9443c01a7336-2d6f80c76e6so6440725ad.3 for ; Tue, 01 Sep 2026 17:38:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1788309534; x=1788914334; darn=lists.infradead.org; h=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=FaTmFFkWvtpI1wxK9lbUH5Q49TqxcdmMs9wtskLlSB4=; b=GDlBmLmFd9zKUYI6ESZlRU47LCkhklO1k/R/jDXM1HhM94rAmlyxJdMKt+Hi8FScDV PPtxDyBvHJ4PmjypZ1mIJksHLjzd/b/EBvemIyRz0aHma3OgvLYFpieh158y22//FlZ6 a/ibJh2Duj70afxDRHza+lMmrSZqaqawTOgCOiMjrYd7kcwFUipcaqfCdn6vJeXyUJCX jxsdrv/fDkBco+s1Ru4tQO8P6I8p5J5zJkt3XeGvBk71yLp+IydCdh1Djed7eaT9Eqzk 2kVvq89Qi2tQqqh1+ndcE8KapqisT2MNblK/y5DexdFsMob+e8V0QxsFA0m0nqHMzcdJ AtZg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1788309534; x=1788914334; h=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=FaTmFFkWvtpI1wxK9lbUH5Q49TqxcdmMs9wtskLlSB4=; b=LVF68sCk5AuASFBMH8RbVkCGlXR6YS2El5me/ZzS19lu6yXVaqNXybdriUfyZGfl5D yxUVjLi6fVRdwRBXarDzOXIX0+rbGV/Ora+RXYtQjd0sk5wCaKnECuwPuqOqAWak89xW cgCad21AKn11tPEze0CcQyJj0xj1mzaC4d60+Tig95NKe+WeSYUBsBVYH4s3cRZH1oMl Kg/4+D7wjNY6wrUyahDxvNkAbeDFkIIyibkKYqU63DAGzOSQPSc0AtJfGq/zVEFn7Ei1 Dh9iJus4i/60M5+TmwC22CZ2COZUqurZD46aMh9Cr/WGFXdUtnrlvnNQo5amsxHVxyCP RnEg== X-Forwarded-Encrypted: i=1; AKwUvBzvPMbwFPXWJhCkjlGB2FfOpnAx27RDpPKn6jzFhkw6x3kApCKfRY7M37EW0bfnt9jWMkKzdA5jAMp7iovOzP93@lists.infradead.org X-Gm-Message-State: AFuF++kqwRoC0zrUH4nywoe73Py5laQDfbfSWty/jLunC8tsnZQxlTYT ZbyxQ+vXmo4nxyYyGmpu3aTQcpKq8GK9YgJdaBfzvBEyUE4fLe2vQSq3AnlZjaqVwX7kv5dj/9d bEZj0FA== X-Received: from plgf7.prod.google.com ([2002:a17:902:ce87:b0:2cc:6063:a658]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:26c6:b0:2d8:d4cc:be67 with SMTP id d9443c01a7336-2daec73f1d2mr14199535ad.20.1788309534336; Tue, 01 Sep 2026 17:38:54 -0700 (PDT) Date: Tue, 1 Sep 2026 17:38:53 -0700 In-Reply-To: <20260831144802.834315-4-seiden@linux.ibm.com> Mime-Version: 1.0 References: <20260831144802.834315-1-seiden@linux.ibm.com> <20260831144802.834315-4-seiden@linux.ibm.com> Message-ID: Subject: Re: [PATCH v7 03/23] KVM: Allow KVM implementations to switch off MMIO independent of Kconfig From: Sean Christopherson To: Steffen Eiden Cc: kvm@vger.kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, Alexander Gordeev , Andreas Grapentin , Arnd Bergmann , Catalin Marinas , Christian Borntraeger , Claudio Imbrenda , David Hildenbrand , Friedrich Welter , Fuad Tabba , Gautam Gala , Hariharan Mari , Heiko Carstens , Hendrik Brueckner , Ilya Leoshkevich , Janosch Frank , Joey Gouly , Marc Zyngier , Nico Boehr , Nina Schoetterl-Glausch , Oliver Upton , Paolo Bonzini , Suzuki K Poulose , Sven Schnelle , Ulrich Weigand , Vasily Gorbik , Will Deacon , Zenghui Yu Content-Type: text/plain; charset="us-ascii" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260901_173856_061321_2D2AECA1 X-CRM114-Status: GOOD ( 11.79 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Aug 31, 2026, Steffen Eiden wrote: > Only defining KVM_MMIO is not flexible enough for multi-KVM systems > where one KVM implements MMIO but others do not. Solve this by > additionally testing for the non-existence of KVM_NO_MMIO before > including MMIO code to KVM. Ewwwww. IIUC, s390 ends up with two KVM modules, i.e. there really are two different KVMs being built. Rather than have a KVM_MMIO and NO_KVM_MMIO, I vote very strongly to drop CONFIG_KVM_MMIO entirely and replace it with __KVM_HAVE_ARCH_MMIO, a la __KVM_HAVE_ARCH_VM_FREE and others. Tracking two separate macros is going to be annoying to maintain, and will definitely be confusing for non-s390 people. It'll mean linking in an emtpy coalesced_mmio.o on s390 when building without arm64 support, but I'm guessing that won't be at all common for s390 builds.