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Tsirkin" , Peter Maydell , qemu-block@nongnu.org, Stefan Hajnoczi , Kevin Wolf , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= Subject: [PATCH 20/31] hw/net/tulip: skip automatic zero-init of large array Date: Tue, 10 Jun 2025 13:36:58 +0100 Message-ID: <20250610123709.835102-21-berrange@redhat.com> In-Reply-To: <20250610123709.835102-1-berrange@redhat.com> References: <20250610123709.835102-1-berrange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@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, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1749559186424116600 The 'tulip_setup_frame' method has a 4k byte array used for copynig DMA data from the device. Skip the automatic zero-init of this array to eliminate the performance overhead in the I/O hot path. The 'buf' array will be fully initialized when reading data from the device. Signed-off-by: Daniel P. Berrang=C3=A9 --- hw/net/tulip.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/hw/net/tulip.c b/hw/net/tulip.c index 63fe513458..319af906c8 100644 --- a/hw/net/tulip.c +++ b/hw/net/tulip.c @@ -629,7 +629,7 @@ static void tulip_setup_filter_addr(TULIPState *s, uint= 8_t *buf, int n) static void tulip_setup_frame(TULIPState *s, struct tulip_descriptor *desc) { - uint8_t buf[4096]; + QEMU_UNINITIALIZED uint8_t buf[4096]; int len =3D (desc->control >> TDES1_BUF1_SIZE_SHIFT) & TDES1_BUF1_SIZE= _MASK; int i; =20 --=20 2.49.0