From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753082AbeAFUAx (ORCPT + 1 other); Sat, 6 Jan 2018 15:00:53 -0500 Received: from mail-wm0-f66.google.com ([74.125.82.66]:37275 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752166AbeAFUAw (ORCPT ); Sat, 6 Jan 2018 15:00:52 -0500 X-Google-Smtp-Source: ACJfBouJGtN8a+6ROvSbYSTHrOI/7n3yAOpiotqwfr5xC1XYy4+6XGNAST04SNnvKpaq3n5a/8JIsw== Subject: Re: [PATCH] vboxvideo: Fix incorrect type in assignment sparse warning To: Alexander Kapshuk Cc: Greg KH , michael.thayer@oracle.com, dri-devel@lists.freedesktop.org, peda@axentia.se, Daniel Vetter , =?UTF-8?Q?Cihangir_Akt=c3=bcrk?= , Sean Paul , linux-kernel References: <6f4de025-b126-9819-d789-ef611c9f82d9@redhat.com> From: Hans de Goede Message-ID: <8ab17864-c94f-5dd8-defe-3cda42f862b9@redhat.com> Date: Sat, 6 Jan 2018 21:00:49 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: Hi, On 06-01-18 20:56, Alexander Kapshuk wrote: > On Sat, Jan 6, 2018 at 9:43 PM, Hans de Goede wrote: >> HI, >> >> >> On 06-01-18 20:30, Alexander Kapshuk wrote: >>> >>> On Sat, Jan 6, 2018 at 6:00 PM, Hans de Goede wrote: >>>> >>>> Hi, >>>> >>>> >>>> On 06-01-18 15:20, Alexander Kapshuk wrote: >>>>> >>>>> >>>>> On Mon, Dec 25, 2017 at 04:42:59PM +0200, Alexander Kapshuk wrote: >>>>>> >>>>>> >>>>>> Sparse emitted the following warning: >>>>>> ../drivers/staging/vboxvideo/vbox_fb.c:173:27: warning: incorrect type >>>>>> in >>>>>> assignment (different address spaces) >>>>>> ../drivers/staging/vboxvideo/vbox_fb.c:173:27: expected char >>>>>> [noderef] >>>>>> *screen_base >>>>>> ../drivers/staging/vboxvideo/vbox_fb.c:173:27: got void *virtual >>>>>> >>>>>> The vbox_bo buffer object kernel mapping is handled by a call >>>>>> to ttm_bo_kmap() prior to the assignment of bo->kmap.virtual to >>>>>> info->screen_base of type char __iomem*. >>>>>> Casting bo->kmap.virtual to char __iomem* in this assignment fixes >>>>>> the warning. >>>>>> >>>>>> vboxvideo: Fix address space of expression removal sparse warning >>>>>> >>>>>> Sparse emitted the following warning: >>>>>> ../drivers/staging/vboxvideo/vbox_main.c:64:25: warning: cast removes >>>>>> address space of expression >>>>>> >>>>>> vbox->vbva_buffers iomapping is handled by calling vbox_accel_init() >>>>>> from vbox_hw_init(). >>>>>> __force attribute is used in assignment to vbva to fix the warning. >>>>>> >>>>>> Signed-off-by: Alexander Kapshuk >>>>>> --- >>>>>> drivers/staging/vboxvideo/vbox_fb.c | 2 +- >>>>>> drivers/staging/vboxvideo/vbox_main.c | 2 +- >>>>>> 2 files changed, 2 insertions(+), 2 deletions(-) >>>>>> >>>>>> diff --git a/drivers/staging/vboxvideo/vbox_fb.c >>>>>> b/drivers/staging/vboxvideo/vbox_fb.c >>>>>> index 8aed248db6e2..43c39eca4ae1 100644 >>>>>> --- a/drivers/staging/vboxvideo/vbox_fb.c >>>>>> +++ b/drivers/staging/vboxvideo/vbox_fb.c >>>>>> @@ -170,7 +170,7 @@ static int vboxfb_create(struct drm_fb_helper >>>>>> *helper, >>>>>> drm_fb_helper_fill_var(info, &fbdev->helper, sizes->fb_width, >>>>>> sizes->fb_height); >>>>>> >>>>>> - info->screen_base = bo->kmap.virtual; >>>>>> + info->screen_base = (char __iomem *)bo->kmap.virtual; >>>>>> info->screen_size = size; >>>>>> >>>>>> #ifdef CONFIG_DRM_KMS_FB_HELPER >>>> >>>> >>>> >>>> This fix looks good to me. >>>> >>>>>> diff --git a/drivers/staging/vboxvideo/vbox_main.c >>>>>> b/drivers/staging/vboxvideo/vbox_main.c >>>>>> index 80bd039fa08e..973b3bcc04b1 100644 >>>>>> --- a/drivers/staging/vboxvideo/vbox_main.c >>>>>> +++ b/drivers/staging/vboxvideo/vbox_main.c >>>>>> @@ -61,7 +61,7 @@ void vbox_enable_accel(struct vbox_private *vbox) >>>>>> if (vbox->vbva_info[i].vbva) >>>>>> continue; >>>>>> >>>>>> - vbva = (void *)vbox->vbva_buffers + i * >>>>>> VBVA_MIN_BUFFER_SIZE; >>>>>> + vbva = (void __force *)vbox->vbva_buffers + i * >>>>>> VBVA_MIN_BUFFER_SIZE; >>>>>> if (!vbva_enable(&vbox->vbva_info[i], >>>>>> vbox->guest_pool, vbva, i)) { >>>>>> /* very old host or driver error. */ >>>> >>>> >>>> >>>> Hmm, isn't there a cleaner way to fix this ? Maybe make vbva_enable's >>>> argument (and the local vbva variable) of type u8 __iomem * too ? >>>> >>>> Regards, >>>> >>>> Hans >>> >>> >>> Hi Hans, >>> >>> Thanks for your prompt response. >>> >>> I had a good look at the vbva_enable() function's definition and to >>> the best of my knowledge, changing vbva's type from 'struct >>> vbva_buffer *' to 'u8 __iomem *' wouldn't work. >>> vbva_enable() relies on vbva's type being a pointer to 'struct >>> vbva_buffer': >>> vbva's memory gets set to zero; >>> some of vbva's members are initialised to particular values; >>> vbva_ctx->vbva expects vbva to be a pointer to 'struct vbva_buffer' as >>> well; >>> >>> Or am I misreading this? >> >> >> No your not misreading this I did not check the function myself before >> commenting myself, my bad. > > Thanks for confirming my understanding of this. > >> >>> What are your thoughts on this? >> >> >> Lets just move ahead with your original fix: > > Did you want me to resend the patch, or is someone going to pull the > original one I sent into their tree? > Thanks. I expect Greg to pick it up without a resend. But with all the Spectre stuff going on right now he might miss it, so I would say give it 14 days and if he has not picked it up by then, resend it with my reviewed-by added. Regards, Hans