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Thu, 17 Dec 2020 12:15:49 -0800 (PST) MIME-Version: 1.0 References: <20201211100908.19696-1-cfontana@suse.de> <20201211100908.19696-8-cfontana@suse.de> In-Reply-To: From: Peter Maydell Date: Thu, 17 Dec 2020 20:15:38 +0000 Message-ID: Subject: Re: dangers of current NEED_CPU_H, CONFIG_SOFTMMU, CONFIG_USER_ONLY (was: [PATCH v11 7/7] cpu: introduce cpu_accel_instance_init) To: Claudio Fontana Content-Type: text/plain; charset="UTF-8" Received-SPF: pass client-ip=2a00:1450:4864:20::632; envelope-from=peter.maydell@linaro.org; helo=mail-ej1-x632.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, 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: Eduardo Habkost , =?UTF-8?Q?Philippe_Mathieu=2DDaud=C3=A9?= , Richard Henderson , QEMU Developers , =?UTF-8?B?TWFyYy1BbmRyw6kgTHVyZWF1?= , Paolo Bonzini , Alex Bennee Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, 17 Dec 2020 at 19:46, Claudio Fontana wrote: > > Hi, > > I would like to highlight the current dangerous state of NEED_CPU_H / CONFIG_SOFTMMU / CONFIG_USER_ONLY. > So our struct TcgCpuOperations in include/hw/core/cpu.h, > which contains after this series: > > #ifndef CONFIG_USER_ONLY > /** > * @do_transaction_failed: Callback for handling failed memory transactions > * (ie bus faults or external aborts; not MMU faults) > */ > void (*do_transaction_failed)(CPUState *cpu, hwaddr physaddr, vaddr addr, > unsigned size, MMUAccessType access_type, > int mmu_idx, MemTxAttrs attrs, > MemTxResult response, uintptr_t retaddr); > /** > * @do_unaligned_access: Callback for unaligned access handling > */ > void (*do_unaligned_access)(CPUState *cpu, vaddr addr, > MMUAccessType access_type, > int mmu_idx, uintptr_t retaddr); > #endif /* !CONFIG_USER_ONLY */ Yeah, don't try to ifdef out struct fields in common-compiled code... > Note that include/hw/core/cpu.h already uses CONFIG_USER_ONLY in other parts of the header file, and we might have hidden problems as a result we (or at least I) don't know about, > because code is being compiled in for linux-user which explicitly should not be compiled there. The other CONFIG_USER_ONLY checks in that file are only ifdeffing out prototypes for functions that exist only in the softmmu build, or providing do-nothing stubs for functions that are softmmu only. I think they're safe. > There are multiple workarounds / fixes possible for my short term problem, > but would it not be a good idea to fix this problem at its root once and for all? What's your proposal for fixing things ? Incidentally, this should not be a problem for CONFIG_SOFTMMU, because that is listed in include/exec/poison.h so trying to use it in a common (not compiled-per-target) file will give you a compile error. (So in theory we could make CONFIG_USER_ONLY a poisoned identifier but that will require some work to adjust places where we currently use it in "safe" ways...) thanks -- PMM