linux-kernel - Re: [PATCH 2/2] udmabuf: fix vmap missed offset page

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Message-ID: <70a4ae40-dbfe-a8ff-c4d7-a11c35490b3a@linux.intel.com>
Date: Fri, 25 Apr 2025 10:59:22 +0800
From: Bingbu Cao <bingbu.cao@...ux.intel.com>
To: "Kasireddy, Vivek" <vivek.kasireddy@...el.com>, Huan Yang
 <link@...o.com>, Sumit Semwal <sumit.semwal@...aro.org>,
 Christian König <christian.koenig@....com>,
 Gerd Hoffmann <kraxel@...hat.com>, Andrew Morton
 <akpm@...ux-foundation.org>, Dave Airlie <airlied@...hat.com>,
 "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
 "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
 "linaro-mm-sig@...ts.linaro.org" <linaro-mm-sig@...ts.linaro.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc: "opensource.kernel@...o.com" <opensource.kernel@...o.com>
Subject: Re: [PATCH 2/2] udmabuf: fix vmap missed offset page


On 4/22/25 1:22 PM, Kasireddy, Vivek wrote:
> Hi Huan,
> 
>> Subject: [PATCH 2/2] udmabuf: fix vmap missed offset page
>>
>> Before invoke vmap, we need offer a pages pointer array which each page
>> need to map in vmalloc area.
>>
>> But currently vmap_udmabuf only set each folio's head page into pages,
>> missed each offset pages when iter.
>>
>> This patch set the correctly offset page in each folio into array.
>>
>> Signed-off-by: Huan Yang <link@...o.com>
>> Fixes: 5e72b2b41a21 ("udmabuf: convert udmabuf driver to use folios")
>> ---
>>  drivers/dma-buf/udmabuf.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
>> index 79845565089d..af5200e360a6 100644
>> --- a/drivers/dma-buf/udmabuf.c
>> +++ b/drivers/dma-buf/udmabuf.c
>> @@ -120,7 +120,8 @@ static int vmap_udmabuf(struct dma_buf *buf, struct
>> iosys_map *map)
>>  		return -ENOMEM;
>>
>>  	for (pg = 0; pg < ubuf->pagecount; pg++)
>> -		pages[pg] = &ubuf->folios[pg]->page;
>> +		pages[pg] = folio_page(ubuf->folios[pg],
>> +				       ubuf->offsets[pg] >> PAGE_SHIFT);
> IIUC, it does not look like vm_map_ram() or the other functions it calls would
> write to these tail page pointers (struct page*), which should be safe even
> when HVO is enabled (based on your conversations with Muchun). However,
> I am wondering whether Bingbu can test this out with HVO enabled?

Sorry, I cannot test HVO enabled case. I was running my case with local
revert patch. :)

> 
> Regardless,
> Acked-by: Vivek Kasireddy <vivek.kasireddy@...el.com>
> 
> Thanks,
> Vivek
> 
>>
>>  	vaddr = vm_map_ram(pages, ubuf->pagecount, -1);
>>  	kvfree(pages);
>> --
>> 2.48.1
> 

-- 
Best regards,
Bingbu Cao