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[83.42.66.122]) by smtp.gmail.com with ESMTPSA id e6sm5249829wme.28.2021.07.23.07.14.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 23 Jul 2021 07:14:23 -0700 (PDT) Subject: Re: [PATCH v2 1/1] modules: Improve error message when module is not found To: Claudio Fontana , "Jose R. Ziviani" References: <20210722220952.17444-1-jziviani@suse.de> <20210722220952.17444-2-jziviani@suse.de> <1dec44e9-3587-ff96-f8c4-81399f689e58@suse.de> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: <7eb0823b-289f-90af-7b68-bf3607127ac3@redhat.com> Date: Fri, 23 Jul 2021 16:14:22 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <1dec44e9-3587-ff96-f8c4-81399f689e58@suse.de> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=philmd@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=philmd@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -44 X-Spam_score: -4.5 X-Spam_bar: ---- X-Spam_report: (-4.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.472, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.203, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: pbonzini@redhat.com, richard.henderson@linaro.org, qemu-devel@nongnu.org, Gerd Hoffmann Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 7/23/21 4:02 PM, Claudio Fontana wrote: > On 7/23/21 3:50 PM, Jose R. Ziviani wrote: >> On Fri, Jul 23, 2021 at 11:41:19AM +0200, Claudio Fontana wrote: >>> On 7/23/21 12:09 AM, Jose R. Ziviani wrote: >>>> When a module is not found, specially accelerators, QEMU displays >>>> a error message that not easy to understand[1]. This patch improves >>>> the readability by offering a user-friendly message[2]. >>>> >>>> This patch also moves the accelerator ops check to runtine (instead >>>> of the original g_assert) because it works better with dynamic >>>> modules. >>>> >>>> [1] qemu-system-x86_64 -accel tcg >>>> ERROR:../accel/accel-softmmu.c:82:accel_init_ops_interfaces: assertion failed: >>>> (ops != NULL) >>>> Bail out! ERROR:../accel/accel-softmmu.c:82:accel_init_ops_interfaces: >>>> assertion failed: (ops != NULL) >>>> 31964 IOT instruction (core dumped) ./qemu-system-x86_64 ... >>>> >>>> [2] qemu-system-x86_64 -accel tcg >>>> accel-tcg-x86_64 module is missing, install the package or config the library path correctly. >>>> >>>> Signed-off-by: Jose R. Ziviani >>>> --- >>>> accel/accel-softmmu.c | 5 ++++- >>>> util/module.c | 14 ++++++++------ >>>> 2 files changed, 12 insertions(+), 7 deletions(-) >>>> >>>> diff --git a/accel/accel-softmmu.c b/accel/accel-softmmu.c >>>> index 67276e4f52..52449ac2d0 100644 >>>> --- a/accel/accel-softmmu.c >>>> +++ b/accel/accel-softmmu.c >>>> @@ -79,7 +79,10 @@ void accel_init_ops_interfaces(AccelClass *ac) >>>> * all accelerators need to define ops, providing at least a mandatory >>>> * non-NULL create_vcpu_thread operation. >>>> */ >>>> - g_assert(ops != NULL); >>>> + if (ops == NULL) { >>>> + exit(1); >>>> + } >>>> + >>> >>> >>> Ah, again, why? >>> This change looks wrong to me, >>> >>> the ops code should be present when ops interfaces are initialized: >>> it should be a code level assertion, as it has to do with the proper order of initializations in QEMU, >>> >>> why would we want to do anything else but to assert here? >>> >>> Am I blind to something obvious? >> >> Hello! >> >> Thank you for reviewing it! >> >> The problem is that if your TCG module is not installed and you start >> QEMU like: >> >> ./qemu-system-x86_64 -accel tcg >> >> You'll get the error message + a crash with a core dump: >> >> accel-tcg-x86_64 module is missing, install the package or config the library path correctly. >> ** >> ERROR:../accel/accel-softmmu.c:82:accel_init_ops_interfaces: assertion failed: (ops != NULL) >> Bail out! ERROR:../accel/accel-softmmu.c:82:accel_init_ops_interfaces: assertion failed: (ops != NULL) >> [1] 5740 IOT instruction (core dumped) ./qemu-system-x86_64 -accel tcg >> >> I was digging a little bit more in order to move this responsibility to >> module.c but there isn't enough information there to safely exit() in >> all situations that a module may be loaded. As Gerd mentioned, more work >> is needed in order to achieve that. >> >> However, it's not nice to have a crash due to an optional module missing. >> It's specially confusing because TCG has always been native. Considering >> also that we're already in hard freeze for 6.1, I thought to have this >> simpler check instead. >> >> What do you think if we have something like: >> >> /* FIXME: this isn't the right place to handle a missing module and >> must be reverted when the module refactoring is completely done */ >> #ifdef CONFIG_MODULES >> if (ops == NULL) { >> exit(1); >> } >> #else >> g_assert(ops != NULL); >> #endif >> >> Regards! > > > For the normal builds (without modular tcg), this issue does not appear right? > So maybe there is no pressure to change anything for 6.1, and we can work on the right solution on master? > > Not sure how we consider this feature for 6.1, I guess it is still not a supported option, > (is there any CI for this? Probably not right?), > > so I would consider building modular tcg in 6.1 as "experimental", and we can proceed to do the right thing on master? +1 as I don't see this feature ready.