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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=-1, RCVD_IN_MSPIKE_WL=-0.01, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 8/10/25 01:26, Richard Henderson wrote: > On 8/9/25 04:59, Paolo Bonzini wrote: >> +void tcg_kick_vcpu_thread(CPUState *cpu) >> +{ >> +    /* >> +     * Ensure cpu_exec will see the reason why the exit request was set. >> +     * FIXME: this is not always needed.  Other accelerators instead >> +     * read interrupt_request and set exit_request on demand from the >> +     * CPU thread; see kvm_arch_pre_run() for example. >> +     */ >> +    qatomic_store_release(&cpu->exit_request, 1); >> + >> +    /* Ensure cpu_exec will see the exit request after TCG has >> exited.  */ >> +    qatomic_store_release(&cpu->neg.icount_decr.u16.high, -1); >> +} > > So, now both cpu_exit and cpu_kick set exit_request. > > You ifdef this out again for user-only in patch 7, but this does suggest > that kick and exit are essentially interchangeable.  You rearrange > things a bit in patch 6, but it's still not clear to me what the > difference between the two should be.  There's certainly nothing at all > in include/hw/core/cpu.h to differentiate them. > > Should we instead eliminate one of kick or exit, unifying the paths? In cpu-exec.c terms, qemu_cpu_kick() *should* go out to cpu_handle_interrupt() whereas cpu_exit() *should* go out to cpu_handle_exception(). The difference matters for some accelerators where qemu_cpu_kick() tries not to take the BQL in the vCPU thread. Until now TCG's implementation of kick_vcpu_thread set both exit_request and interrupt_request, and I'm not changing that yet for system emulation. Patch 7 does that for user-mode emulation, because it's trivial: neither linux-user not bsd-user use qemu_cpu_kick() directly. Paolo