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[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> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221103_083009_771386_FE782BE9 X-CRM114-Status: GOOD ( 22.75 ) 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: , Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel