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

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Message-ID: <IA0PR11MB7185796FAA2A065CBE4EAB37F8BB2@IA0PR11MB7185.namprd11.prod.outlook.com>
Date: Tue, 22 Apr 2025 05:22:25 +0000
From: "Kasireddy, Vivek" <vivek.kasireddy@...el.com>
To: 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>,
	"bingbu.cao@...ux.intel.com" <bingbu.cao@...ux.intel.com>
Subject: RE: [PATCH 2/2] udmabuf: fix vmap missed offset page

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?

Regardless,
Acked-by: Vivek Kasireddy <vivek.kasireddy@...el.com>

Thanks,
Vivek

> 
>  	vaddr = vm_map_ram(pages, ubuf->pagecount, -1);
>  	kvfree(pages);
> --
> 2.48.1