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(unknown [109.252.117.89]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: dmitry.osipenko) by madras.collabora.co.uk (Postfix) with ESMTPSA id 2A553660220B; Mon, 6 Mar 2023 14:33:05 +0000 (GMT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1678113186; bh=gJrshKNUaitWNWbqYmQJvTDpbgAcQ7xq5COOHL06j48=; h=From:To:Cc:Subject:Date:From; b=VGYL25Nk+XguA0di2RClfj+YaJ7Z/yUfecAaaKgHQlu2cWiveT+N/ZkiXqQZ7ZBfv 66hnylM0mBMgus89gmzTNnWbJ5fzRbSOwmj3OvyO+r0TaunD8uhDqxKjtiKU8aSCfL 84WVBND/GmoitV0965ylpRG9ZH5dUyvGdMHljXxFK0eFR6FeKjlR8VrZm9R5KcWZD5 rwv5qfVlh7YdYgOVpo7N9mKKcxS18BDm4NUikrXb0kcpjV0XCmu9hNesHp+si7H06b xdi+mkCoOcffTEpKjTRORXPfUkLg5RgpVmdShpmTICo5TdD2fa/lvWmSEjPneOFf9t bnDfiWFXi1A1A== From: Dmitry Osipenko To: Gerd Hoffmann , Rob Clark Cc: Gurchetan Singh , Chia-I Wu , Ryan Neph , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Javier Martinez Canillas , David Airlie , kernel@collabora.com, virtualization@lists.linux-foundation.org Subject: [PATCH v2] drm/virtio: Fix handling CONFIG_DRM_VIRTIO_GPU_KMS option Date: Mon, 6 Mar 2023 17:32:34 +0300 Message-Id: <20230306143234.1561759-1-dmitry.osipenko@collabora.com> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1759629816736230056?= X-GMAIL-MSGID: =?utf-8?q?1759629816736230056?= VirtIO-GPU got a new config option for disabling KMS. There were two problems left unnoticed during review when the new option was added: 1. The IS_ENABLED(CONFIG_DRM_VIRTIO_GPU_KMS) check in the code was inverted, hence KMS was disabled when it should be enabled and vice versa. 2. The disabled KMS crashed kernel with a NULL dereference in drm_kms_helper_hotplug_event(), which shall not be invoked with a disabled KMS. Fix the inverted config option check in the code and skip handling the VIRTIO_GPU_EVENT_DISPLAY sent by host when KMS is disabled in guest to fix the crash. Fixes: 72122c69d717 ("drm/virtio: Add option to disable KMS support") Signed-off-by: Dmitry Osipenko Acked-by: Gerd Hoffmann --- Changelog: v2: - Moved the "has_edid" under the "num_scanouts" condition, like was suggested by Gerd Hoffmann. drivers/gpu/drm/virtio/virtgpu_kms.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/virtio/virtgpu_kms.c b/drivers/gpu/drm/virtio/virtgpu_kms.c index 874ad6c2621a..15f2519988e7 100644 --- a/drivers/gpu/drm/virtio/virtgpu_kms.c +++ b/drivers/gpu/drm/virtio/virtgpu_kms.c @@ -43,11 +43,13 @@ static void virtio_gpu_config_changed_work_func(struct work_struct *work) virtio_cread_le(vgdev->vdev, struct virtio_gpu_config, events_read, &events_read); if (events_read & VIRTIO_GPU_EVENT_DISPLAY) { - if (vgdev->has_edid) - virtio_gpu_cmd_get_edids(vgdev); - virtio_gpu_cmd_get_display_info(vgdev); - virtio_gpu_notify(vgdev); - drm_helper_hpd_irq_event(vgdev->ddev); + if (vgdev->num_scanouts) { + if (vgdev->has_edid) + virtio_gpu_cmd_get_edids(vgdev); + virtio_gpu_cmd_get_display_info(vgdev); + virtio_gpu_notify(vgdev); + drm_helper_hpd_irq_event(vgdev->ddev); + } events_clear |= VIRTIO_GPU_EVENT_DISPLAY; } virtio_cwrite_le(vgdev->vdev, struct virtio_gpu_config, @@ -224,7 +226,7 @@ int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev) vgdev->num_scanouts = min_t(uint32_t, num_scanouts, VIRTIO_GPU_MAX_SCANOUTS); - if (IS_ENABLED(CONFIG_DRM_VIRTIO_GPU_KMS) || !vgdev->num_scanouts) { + if (!IS_ENABLED(CONFIG_DRM_VIRTIO_GPU_KMS) || !vgdev->num_scanouts) { DRM_INFO("KMS disabled\n"); vgdev->num_scanouts = 0; vgdev->has_edid = false;