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 mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by smtp.lore.kernel.org (Postfix) with ESMTP id 97C81C43219 for ; Thu, 3 Nov 2022 15:30:07 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id EAFCD4B5F4; Thu, 3 Nov 2022 11:30:06 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Authentication-Results: mm01.cs.columbia.edu (amavisd-new); dkim=softfail (fail, message has been altered) header.i=@google.com Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Fqqrl+Z42J4y; Thu, 3 Nov 2022 11:30:05 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id C18E34B62D; Thu, 3 Nov 2022 11:30:05 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 5C7B84B269 for ; Thu, 3 Nov 2022 11:30:04 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id RZUd7YNdRVi6 for ; Thu, 3 Nov 2022 11:30:03 -0400 (EDT) Received: from mail-pf1-f179.google.com (mail-pf1-f179.google.com [209.85.210.179]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 38AE84B210 for ; Thu, 3 Nov 2022 11:30:03 -0400 (EDT) Received: by mail-pf1-f179.google.com with SMTP id b29so1907548pfp.13 for ; Thu, 03 Nov 2022 08:30:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=UyUe+HbRzSrTdJquQCMiaXWC2coZG28I37xguDaJaYg=; b=JxP3em5mMEo8M/seyYjwqQClKWueZhrkefM7iopEbtJ9U0ARhXsBBlBaHvB0YZ+mCq 7I2lDIbzgsTnUJXXFFd+Mf2MRkvMQ3d/mi120+0k+co+feliF2fGnlDGLipP3oo4jHIs yhCQnzB0LNdLsoCiyP2ThdGCDug/wevVBzx4ZCIoRVJzM62ULFanZrMyKnrfoLhgGw7L LE3NJVvLI80qGdb5QUdNBUYtcEfD6sTxNonp/rLGuh5no7R8ACiBwreWQkoFJnyoE1Nq joZ/uzznkWHqO7mwwbSR52gm1kYa+vf+hliw2Y9f1o05+cN6N5swUWJ7vJszMr5BEKoW HTcg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=UyUe+HbRzSrTdJquQCMiaXWC2coZG28I37xguDaJaYg=; b=WDrfsjs9muI1VY9sqiEag9Nj4uRF3UZy83DXSocnfA6E6H0dnEsljabidOI7FqkgZr bVhSYVB/7husId6rKtNnKS2vG+NmkYF66F7B0JHFCpM3UNpgbdasOFg170R7iFADLmu0 gsbbVeHYxctrBIYq2u4ZcH7ZA2LqH1/YnAbQZQKhPxkt8BaLXCSwAbRS9eT+m5oMgV4/ O1620m4YL5gXrl+um3oT8szb134bK2+gJM8F9tVBf08iO9cenZNvEE5gWjyC1Z4zSw4A sOSZFWDA0eowNGO+WlfvfSwtfe67KuoEbJTofhUBEIr7RdWlnkGRTu45lc4u0juFyirF el+A== X-Gm-Message-State: ACrzQf3eprpGtKAxG4IF9PqDbnsZhGJWW7+A04JSV3oGErqIIHiqB0lQ 7zOqF1pOGB8SEVzTupAI8j4HbQ== X-Google-Smtp-Source: AMsMyM6by5WQXi0G4lBZGaavWsGrxKC8DeWyAUbAtvZsM8BboB9ucyemIyMYLKoI4FadI1MlyxYOPw== X-Received: by 2002:a05:6a00:1996:b0:56d:a845:5789 with SMTP id d22-20020a056a00199600b0056da8455789mr17697890pfl.59.1667489402026; Thu, 03 Nov 2022 08:30:02 -0700 (PDT) Received: from google.com (7.104.168.34.bc.googleusercontent.com. [34.168.104.7]) by smtp.gmail.com with ESMTPSA id f3-20020a170902f38300b0017a018221e2sm835452ple.70.2022.11.03.08.30.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Nov 2022 08:30:01 -0700 (PDT) Date: Thu, 3 Nov 2022 15:29:58 +0000 From: Sean Christopherson To: Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= Subject: Re: [PATCH 17/44] KVM: arm64: Do arm/arch initialiation without bouncing through kvm_init() Message-ID: References: <20221102231911.3107438-1-seanjc@google.com> <20221102231911.3107438-18-seanjc@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Cc: Matthew Rosato , David Hildenbrand , Yuan Yao , Paul Walmsley , linux-kernel@vger.kernel.org, Michael Ellerman , linux-riscv@lists.infradead.org, Claudio Imbrenda , kvmarm@lists.cs.columbia.edu, linux-s390@vger.kernel.org, Janosch Frank , Marc Zyngier , Huacai Chen , Aleksandar Markovic , Christian Borntraeger , Chao Gao , Eric Farman , Albert Ou , kvm@vger.kernel.org, Atish Patra , kvmarm@lists.linux.dev, Thomas Gleixner , linux-arm-kernel@lists.infradead.org, Isaku Yamahata , Fabiano Rosas , linux-mips@vger.kernel.org, Palmer Dabbelt , kvm-riscv@lists.infradead.org, Paolo Bonzini , Vitaly Kuznetsov , linuxppc-dev@lists.ozlabs.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Thu, Nov 03, 2022, Philippe Mathieu-Daud=E9 wrote: > Hi Sean, > = > On 3/11/22 00:18, Sean Christopherson wrote: > > Move arm/arch specific initialization directly in arm's module_init(), > > now called kvm_arm_init(), instead of bouncing through kvm_init() to > > reach kvm_arch_init(). Invoking kvm_arch_init() is the very first acti= on > > performed by kvm_init(), i.e. this is a glorified nop. > > = > > Making kvm_arch_init() a nop will allow dropping it entirely once all > > other architectures follow suit. > > = > > No functional change intended. > > = > > Signed-off-by: Sean Christopherson > > --- > > arch/arm64/kvm/arm.c | 25 ++++++++++++++++--------- > > 1 file changed, 16 insertions(+), 9 deletions(-) > = > > /* NOP: Compiling as a module not supported */ > > void kvm_arch_exit(void) > > { > > - kvm_unregister_perf_callbacks(); > = > Doesn't this belong to the previous patch? No, but the above changelog is a lie, there is very much a functional chang= e here. The goal of the previous patch is to fix the error paths in kvm_arch_init()= , a.k.a. kvm_arm_init(). After fixing kvm_arch_init(), there are still bugs in the = sequence as a whole because kvm_arch_exit() doesn't unwind other state, e.g. kvm_arc= h_exit() should really look something like: void kvm_arch_exit(void) { teardown_subsystems(); if (!is_kernel_in_hyp_mode()) teardown_hyp_mode(); kvm_arm_vmid_alloc_free(); if (is_protected_kvm_enabled()) ??? = } Becuase although the comment "NOP: Compiling as a module not supported" is = correct about KVM ARM always having to be built into the kernel, kvm_arch_exit() ca= n still be called if a later stage of kvm_init() fails. But rather than add a patch to fix kvm_arch_exit(), I chose to fix the bug = by moving code out of kvm_arch_init() so that the unwind sequence established = in the previous patch could be reused. Except I managed to forget those details when writing the changelog. The c= hangelog should instead be: KVM: arm64: Do arm/arch initialization without bouncing through kvm_init() = Do arm/arch specific initialization directly in arm's module_init(), now called kvm_arm_init(), instead of bouncing through kvm_init() to reach kvm_arch_init(). Invoking kvm_arch_init() is the very first action performed by kvm_init(), so from a initialization perspective this is a glorified nop. = Avoiding kvm_arch_init() also fixes a mostly benign bug as kvm_arch_exit() doesn't properly unwind if a later stage of kvm_init() fails. While the soon-to-be-deleted comment about compiling as a module being unsupported is correct, kvm_arch_exit() can still be called by kvm_init() if any step after the call to kvm_arch_init() succeeds. Add a FIXME to call out that pKVM initialization isn't unwound if kvm_init() fails, which is a pre-existing problem inherited from kvm_arch_exit(). Making kvm_arch_init() a nop will also allow dropping kvm_arch_init() and kvm_arch_exit() entirely once all other architectures follow suit. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f177.google.com (mail-pf1-f177.google.com [209.85.210.177]) (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 CDB167492 for ; Thu, 3 Nov 2022 15:30:02 +0000 (UTC) Received: by mail-pf1-f177.google.com with SMTP id g62so1920012pfb.10 for ; Thu, 03 Nov 2022 08:30:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=UyUe+HbRzSrTdJquQCMiaXWC2coZG28I37xguDaJaYg=; b=JxP3em5mMEo8M/seyYjwqQClKWueZhrkefM7iopEbtJ9U0ARhXsBBlBaHvB0YZ+mCq 7I2lDIbzgsTnUJXXFFd+Mf2MRkvMQ3d/mi120+0k+co+feliF2fGnlDGLipP3oo4jHIs yhCQnzB0LNdLsoCiyP2ThdGCDug/wevVBzx4ZCIoRVJzM62ULFanZrMyKnrfoLhgGw7L LE3NJVvLI80qGdb5QUdNBUYtcEfD6sTxNonp/rLGuh5no7R8ACiBwreWQkoFJnyoE1Nq joZ/uzznkWHqO7mwwbSR52gm1kYa+vf+hliw2Y9f1o05+cN6N5swUWJ7vJszMr5BEKoW HTcg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=UyUe+HbRzSrTdJquQCMiaXWC2coZG28I37xguDaJaYg=; b=6YGJTGgoCOOjV0D2ckyjUzZnwBF0nJJFhEn9QzTuIr2XXXTmtng8uUk3uWenc4OFiW QsUNJf0G8Q/uH4PxiY6FLmFs65lyCsFS4wQHHrOmJqDvTtRcnFZonJRND8GNVtpBSfgP b1KDdedgq0QrAHZO1iQcmMW43qmAA4NAWStrbOVLSuog5L+khqiEYCZlyW6l85jwe0i+ hl/R44U6CYY7sGOazRrFoKFfzgYS4QiT5zvtmCYkTPGsSFyTzNF58NoR6px5IfMP6AHM 81VCwmRpnRd+7oSw13OlrYpPm32tNFfIj87TWR9ZS/iDLQAvlzTz/xCV+7RCO+hWcrVP 2qVA== X-Gm-Message-State: ACrzQf0o755SMKWs4RysAnK4d4KqxNsO16fpJ1eGdvnb+93UBL1VqnsI 6Rs9i55eEajnK313bq8ho0hndw== X-Google-Smtp-Source: AMsMyM6by5WQXi0G4lBZGaavWsGrxKC8DeWyAUbAtvZsM8BboB9ucyemIyMYLKoI4FadI1MlyxYOPw== X-Received: by 2002:a05:6a00:1996:b0:56d:a845:5789 with SMTP id d22-20020a056a00199600b0056da8455789mr17697890pfl.59.1667489402026; Thu, 03 Nov 2022 08:30:02 -0700 (PDT) Received: from google.com (7.104.168.34.bc.googleusercontent.com. [34.168.104.7]) by smtp.gmail.com with ESMTPSA id f3-20020a170902f38300b0017a018221e2sm835452ple.70.2022.11.03.08.30.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Nov 2022 08:30:01 -0700 (PDT) Date: Thu, 3 Nov 2022 15:29:58 +0000 From: Sean Christopherson To: Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= Cc: Paolo Bonzini , Marc Zyngier , Huacai Chen , Aleksandar Markovic , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Matthew Rosato , Eric Farman , Vitaly Kuznetsov , James Morse , Alexandru Elisei , Suzuki K Poulose , Oliver Upton , Atish Patra , David Hildenbrand , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, linux-mips@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, Isaku Yamahata , Fabiano Rosas , Michael Ellerman , Chao Gao , Thomas Gleixner , Yuan Yao Subject: Re: [PATCH 17/44] KVM: arm64: Do arm/arch initialiation without bouncing through kvm_init() Message-ID: References: <20221102231911.3107438-1-seanjc@google.com> <20221102231911.3107438-18-seanjc@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Message-ID: <20221103152958.9np9OIStbdfycz1h6R7xJOXl4fY-AZRDpXckMpIPDnE@z> On Thu, Nov 03, 2022, Philippe Mathieu-Daudé wrote: > Hi Sean, > > On 3/11/22 00:18, Sean Christopherson wrote: > > Move arm/arch specific initialization directly in arm's module_init(), > > now called kvm_arm_init(), instead of bouncing through kvm_init() to > > reach kvm_arch_init(). Invoking kvm_arch_init() is the very first action > > performed by kvm_init(), i.e. this is a glorified nop. > > > > Making kvm_arch_init() a nop will allow dropping it entirely once all > > other architectures follow suit. > > > > No functional change intended. > > > > Signed-off-by: Sean Christopherson > > --- > > arch/arm64/kvm/arm.c | 25 ++++++++++++++++--------- > > 1 file changed, 16 insertions(+), 9 deletions(-) > > > /* NOP: Compiling as a module not supported */ > > void kvm_arch_exit(void) > > { > > - kvm_unregister_perf_callbacks(); > > Doesn't this belong to the previous patch? No, but the above changelog is a lie, there is very much a functional change here. The goal of the previous patch is to fix the error paths in kvm_arch_init(), a.k.a. kvm_arm_init(). After fixing kvm_arch_init(), there are still bugs in the sequence as a whole because kvm_arch_exit() doesn't unwind other state, e.g. kvm_arch_exit() should really look something like: void kvm_arch_exit(void) { teardown_subsystems(); if (!is_kernel_in_hyp_mode()) teardown_hyp_mode(); kvm_arm_vmid_alloc_free(); if (is_protected_kvm_enabled()) ??? } Becuase although the comment "NOP: Compiling as a module not supported" is correct about KVM ARM always having to be built into the kernel, kvm_arch_exit() can still be called if a later stage of kvm_init() fails. But rather than add a patch to fix kvm_arch_exit(), I chose to fix the bug by moving code out of kvm_arch_init() so that the unwind sequence established in the previous patch could be reused. Except I managed to forget those details when writing the changelog. The changelog should instead be: KVM: arm64: Do arm/arch initialization without bouncing through kvm_init() Do arm/arch specific initialization directly in arm's module_init(), now called kvm_arm_init(), instead of bouncing through kvm_init() to reach kvm_arch_init(). Invoking kvm_arch_init() is the very first action performed by kvm_init(), so from a initialization perspective this is a glorified nop. Avoiding kvm_arch_init() also fixes a mostly benign bug as kvm_arch_exit() doesn't properly unwind if a later stage of kvm_init() fails. While the soon-to-be-deleted comment about compiling as a module being unsupported is correct, kvm_arch_exit() can still be called by kvm_init() if any step after the call to kvm_arch_init() succeeds. Add a FIXME to call out that pKVM initialization isn't unwound if kvm_init() fails, which is a pre-existing problem inherited from kvm_arch_exit(). Making kvm_arch_init() a nop will also allow dropping kvm_arch_init() and kvm_arch_exit() entirely once all other architectures follow suit.