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Tsirkin" , Christian Schoenebeck , =?UTF-8?q?Alex=20Benn=C3=A9e?= , qemu-block@nongnu.org, =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , Greg Kurz , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Subject: [PATCH v2 2/6] hw/virtio: Simplify virtio_access_is_big_endian() Date: Wed, 25 Feb 2026 05:19:43 +0100 Message-ID: <20260225041948.52929-3-philmd@linaro.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260225041948.52929-1-philmd@linaro.org> References: <20260225041948.52929-1-philmd@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable 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=2a00:1450:4864:20::336; envelope-from=philmd@linaro.org; helo=mail-wm1-x336.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=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: qemu development 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 @linaro.org) X-ZM-MESSAGEID: 1771993265372158500 From: Pierrick Bouvier Thanks to previous refactoring, we can see more easily it is strictly equivalent to always call virtio_vdev_is_big_endian. static inline bool virtio_vdev_is_big_endian(VirtIODevice *vdev) { if (virtio_vdev_is_legacy(vdev)) { assert(vdev->device_endian !=3D VIRTIO_DEVICE_ENDIAN_UNKNOWN); return vdev->device_endian =3D=3D VIRTIO_DEVICE_ENDIAN_BIG; } /* Devices conforming to VIRTIO 1.0 or later are always LE. */ return false; } The key is to understand that vdev->device_endian is initialized as expected. It always contains cpu endianness, and not device endianness, ignoring if device is legacy or not. By default, it's initialized to vdev->device_endian =3D virtio_default_endian(), which matches target default endianness. Then, on virtio_reset, it will be initialized with current_cpu endianness (if there is one current_cpu). void virtio_reset() { ... if (current_cpu) { /* Guest initiated reset */ vdev->device_endian =3D virtio_current_cpu_endian(); } else { /* System reset */ vdev->device_endian =3D virtio_default_endian(); } Now, we can see how existing virtio_access_is_big_endian is equivalent to virtio_vdev_is_big_endian. Let's break the existing function in its 3 variants, and compare that to virtio_vdev_is_big_endian. static inline bool virtio_access_is_big_endian(VirtIODevice *vdev) - #if defined(LEGACY_VIRTIO_IS_BIENDIAN) return virtio_vdev_is_big_endian(vdev); This is the exact replacement we did, so equivalent. - #elif TARGET_BIG_ENDIAN if (!virtio_vdev_is_legacy(vdev)) { return false; } return true; we know target_is_big_endian(), so vdev->device_endian =3D=3D VIRTIO_DEVICE_ENDIAN_BIG. if (virtio_vdev_is_legacy(vdev)) { return VIRTIO_DEVICE_ENDIAN_BIG =3D=3D VIRTIO_DEVICE_ENDIAN_BIG; } return false; It's written in opposite style compared to existing code (if legacy vs if modern), but it's strictly equivalent. - #else return false; we know !target_is_big_endian(), so vdev->device_endian =3D=3D VIRTIO_DEVICE_ENDIAN_LITTLE. if virtio_vdev_is_legacy(vdev) { return VIRTIO_DEVICE_ENDIAN_LITTLE =3D=3D VIRTIO_DEVICE_ENDIAN_BIG; } return false; So it always return false, as expected. Signed-off-by: Pierrick Bouvier Reviewed-by: Philippe Mathieu-Daud=C3=A9 Acked-by: Stefan Hajnoczi Signed-off-by: Philippe Mathieu-Daud=C3=A9 Reviewed-by: Richard Henderson --- include/hw/virtio/virtio-access.h | 14 -------------- 1 file changed, 14 deletions(-) diff --git a/include/hw/virtio/virtio-access.h b/include/hw/virtio/virtio-a= ccess.h index b8aa7a520f5..e3148c23881 100644 --- a/include/hw/virtio/virtio-access.h +++ b/include/hw/virtio/virtio-access.h @@ -21,23 +21,9 @@ #include "hw/virtio/virtio.h" #include "hw/virtio/virtio-bus.h" =20 -#if defined(TARGET_PPC64) || defined(TARGET_ARM) -#define LEGACY_VIRTIO_IS_BIENDIAN 1 -#endif - static inline bool virtio_access_is_big_endian(VirtIODevice *vdev) { -#if defined(LEGACY_VIRTIO_IS_BIENDIAN) return virtio_vdev_is_big_endian(vdev); -#elif TARGET_BIG_ENDIAN - if (!virtio_vdev_is_legacy(vdev)) { - /* Devices conforming to VIRTIO 1.0 or later are always LE. */ - return false; - } - return true; -#else - return false; -#endif } =20 static inline void virtio_stw_p(VirtIODevice *vdev, void *ptr, uint16_t v) --=20 2.52.0