linux-kernel - Re: [PATCH v2 7/7] accel/rocket: Add IOCTLs for synchronizing memory accesses

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Message-ID: <6cf7d790-57a8-40b9-b5b0-dedfce78d074@quicinc.com>
Date: Fri, 21 Mar 2025 10:15:25 -0600
From: Jeffrey Hugo <quic_jhugo@...cinc.com>
To: Tomeu Vizoso <tomeu@...euvizoso.net>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, Heiko Stuebner <heiko@...ech.de>,
        Oded Gabbay <ogabbay@...nel.org>, Jonathan
 Corbet <corbet@....net>,
        Maarten Lankhorst
	<maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        Sebastian
 Reichel <sebastian.reichel@...labora.com>
CC: <devicetree@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <linux-rockchip@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>, <linux-doc@...r.kernel.org>,
        <linux-media@...r.kernel.org>, <linaro-mm-sig@...ts.linaro.org>
Subject: Re: [PATCH v2 7/7] accel/rocket: Add IOCTLs for synchronizing memory
 accesses

On 2/25/2025 12:55 AM, Tomeu Vizoso wrote:
> +int rocket_ioctl_fini_bo(struct drm_device *dev, void *data, struct drm_file *file)
> +{
> +	struct drm_rocket_fini_bo *args = data;
> +	struct drm_gem_object *gem_obj;
> +	struct rocket_gem_object *rkt_obj;
> +	struct drm_gem_shmem_object *shmem_obj;
> +	struct rocket_device *rdev = to_rocket_device(dev);
> +
> +	gem_obj = drm_gem_object_lookup(file, args->handle);
> +	if (!gem_obj)
> +		return -ENOENT;
> +
> +	rkt_obj = to_rocket_bo(gem_obj);
> +	shmem_obj = &rkt_obj->base;
> +
> +	WARN_ON(rkt_obj->last_cpu_prep_op == 0);
> +
> +	for (unsigned int core = 1; core < rdev->num_cores; core++) {
> +		dma_sync_sgtable_for_device(rdev->cores[core].dev, shmem_obj->sgt,
> +					    rocket_op_to_dma_dir(rkt_obj->last_cpu_prep_op));
> +	}
> +
> +	rkt_obj->last_cpu_prep_op = 0;
> +
> +	drm_gem_object_put(gem_obj);
> +
> +	return 0;
> +}

flags must be 0, and you must check that here. You do not appear to be 
doing that. Otherwise, userspace may put a value in flags, which is 
ignored now, but later when you define flags for a purpose, existing 
userspace will be broken - a uapi violation.