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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id j10sm3446794edj.97.2020.11.26.06.25.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 26 Nov 2020 06:25:03 -0800 (PST) Subject: Re: [PATCH v2 2/6] accel: accel_available() function To: Claudio Fontana , Eduardo Habkost References: <20201125205636.3305257-1-ehabkost@redhat.com> <20201125205636.3305257-3-ehabkost@redhat.com> <12f82771-9db9-8fcd-ea25-736428d2650a@suse.de> <20201126133645.GG2271382@habkost.net> <8d90d611-6545-a478-1316-542dc5424b92@suse.de> From: Paolo Bonzini Message-ID: Date: Thu, 26 Nov 2020 15:25:02 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <8d90d611-6545-a478-1316-542dc5424b92@suse.de> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.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, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=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: Thomas Huth , Gerd Hoffmann , Richard Henderson , qemu-devel@nongnu.org, Roman Bolshakov Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 26/11/20 15:13, Claudio Fontana wrote: > One option I see is simply to document the behavior where > accel_available() is declared in accel.h (ie do not use in fast > path), as well as in accel_find() actually, so that both accel_find() > and accel_available() are avoided in fast path and avoid being called > frequently at runtime. > > Another option could be to remove the allocation completely, and use > for example accel_find(ACCEL_CLASS_NAME("tcg")), or another option > again would be to remove the allocation and use either a fixed buffer > + snprintf, or alloca -like builtin code to use the stack, ... > > Not a big deal, but with a general utility and short name like > accel_available(name) it might be tempting to use this more in the > future? I think it's just that the usecase is not that common. "Is this accelerator compiled in the binary" is not something you need after startup (or if querying the monitor). Paolo