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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D75C3C46CA1 for ; Mon, 18 Sep 2023 16:03:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229778AbjIRQDK (ORCPT ); Mon, 18 Sep 2023 12:03:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229796AbjIRQDK (ORCPT ); Mon, 18 Sep 2023 12:03:10 -0400 Received: from mail-oi1-x24a.google.com (mail-oi1-x24a.google.com [IPv6:2607:f8b0:4864:20::24a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7A5C610EA for ; Mon, 18 Sep 2023 09:02:39 -0700 (PDT) Received: by mail-oi1-x24a.google.com with SMTP id 5614622812f47-3acfa8f8df3so5778543b6e.3 for ; Mon, 18 Sep 2023 09:02:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1695052762; x=1695657562; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=sNXD76U7haNeW91VMZlpdLB8TVqFEiovhx95zes76gg=; b=k72SlCfX3fQYm78wUXNTgG6ok+Pf1dFf32Z6j2EQS+QJX5NmS5eHFaupmDzthJWqb2 6Or7rhB3wQdE7sM6GbHVI4fYL+2IGXieBVw0yJPiEyraoSEvw+2h4go82gA0mAY/hp5V 1NreLFuza6P7XjGN+xzyD3ARsh/lnFg+4/8q0mqJ9Rn3B/dimRSKDqaADoLwcQfJsdaS NwbVRd+azySRzqe5E4yiOIs75QGp1wnTpWZIBwfuBeKvn4VKbGdFAfzWRoOmwHVrHnER HXUWTdiFG1xJirXuLNr3buDYAiKTKjK2IUy3/WaRCqA8WsTgan9LwmFVVDJemWcmbTQA OtfA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695052762; x=1695657562; h=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; bh=sNXD76U7haNeW91VMZlpdLB8TVqFEiovhx95zes76gg=; b=u7dG6qOvWCXjcpAeuMVidYFlX0TWFdlRd05vYCNX+B/Pm88G9c+qgLtgKpYPjqXNOJ 2bWmTFw5MNeVLATLzJUuEIXDqO0QRImSxfuZj05Vt/KlaNtY9g/CzwvPletoGIyDku0i MJQc7JLpb3gBsyd/VeKo2pNmWs+sS+Nb0bM0f8z3768/gCtU9Tfk4wsP77S4eCBD3pG1 zFflbxVz6jifCUV9ObnL7+Rm+riwflklpZPuZNaFz4Il1HVRdeKrpWwvhqjdGwB8gAoz 6b0BIjRJUhLdux5jVgH8ig1pfyVAb7L/hJySzcLM+1QfnXtll+gTYKS83OWAV0t5Kwux QYdA== X-Gm-Message-State: AOJu0YyIgBeuZ+/e5vdsx2nquLoEub645Yr3K9LbWpFIY/bLf1MWqhwT 9GIkaMefGH9veYQdJNB8Unim+dGn9I0= X-Google-Smtp-Source: AGHT+IE1DPoRp0N2nDleDeL+nMknRqhKzdJCPwHMJrwMUBjkYLBNjcfJz91+ASKxJdGzFGGlGgloaP/fXoU= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a25:2411:0:b0:d81:78ec:c403 with SMTP id k17-20020a252411000000b00d8178ecc403mr192905ybk.12.1695052199184; Mon, 18 Sep 2023 08:49:59 -0700 (PDT) Date: Mon, 18 Sep 2023 08:49:57 -0700 In-Reply-To: <20230918152110.GI13795@ziepe.ca> Mime-Version: 1.0 References: <20230916003118.2540661-1-seanjc@google.com> <20230916003118.2540661-6-seanjc@google.com> <20230918152110.GI13795@ziepe.ca> Message-ID: Subject: Re: [PATCH 05/26] vfio: KVM: Pass get/put helpers from KVM to VFIO, don't do circular lookup From: Sean Christopherson To: Jason Gunthorpe Cc: Catalin Marinas , Will Deacon , Marc Zyngier , Oliver Upton , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Peter Zijlstra , Arnaldo Carvalho de Melo , Paolo Bonzini , Tony Krowiak , Halil Pasic , Jason Herne , Harald Freudenberger , Alex Williamson , Andy Lutomirski , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, kvm@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Anish Ghulati , Venkatesh Srinivas , Andrew Thornton Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On Mon, Sep 18, 2023, Jason Gunthorpe wrote: > On Fri, Sep 15, 2023 at 05:30:57PM -0700, Sean Christopherson wrote: > > Explicitly pass KVM's get/put helpers to VFIO when attaching a VM to > > VFIO instead of having VFIO do a symbol lookup back into KVM. Having both > > KVM and VFIO do symbol lookups increases the overall complexity and places > > an unnecessary dependency on KVM (from VFIO) without adding any value. > > > > Signed-off-by: Sean Christopherson > > --- > > drivers/vfio/vfio.h | 2 ++ > > drivers/vfio/vfio_main.c | 74 +++++++++++++++++++--------------------- > > include/linux/vfio.h | 4 ++- > > virt/kvm/vfio.c | 9 +++-- > > 4 files changed, 47 insertions(+), 42 deletions(-) > > I don't mind this, but Christoph had disliked my prior attempt to do > this with function pointers.. > > The get can be inlined, IIRC, what about putting a pointer to the put > inside the kvm struct? That wouldn't allow us to achieve our goal, which is to hide the details of "struct kvm" from VFIO (and the rest of the kernel). What's the objection to handing VFIO a function pointer? > The the normal kvm get/put don't have to exported symbols at all? The export of kvm_get_kvm_safe() can go away (I forgot to do that in this series), but kvm_get_kvm() will hang around as it's needed by KVM sub-modules (PPC and x86), KVMGT (x86), and drivers/s390/crypto/vfio_ap_ops.c (no idea what to call that beast). Gah, KVMGT doesn't actually need to call get/put, that can be handled by kvm_page_track_register_notifier(). I am planning on making exports for sub-modules conditional on there actually being submodules, so that's 2 of the 3 gone, but tackling the s390 crypto driver is an entirely different story.