linux-kernel - Re: [PATCH 1/2] Revert "udmabuf: fix vmap

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Message-ID: <63297d3f-5e37-411e-8150-108a03a01a89@vivo.com>
Date: Wed, 23 Apr 2025 15:22:55 +0800
From: Huan Yang <link@...o.com>
To: "Kasireddy, Vivek" <vivek.kasireddy@...el.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 <bingbu.cao@...ux.intel.com>
Subject: Re: [PATCH 1/2] Revert "udmabuf: fix vmap_udmabuf error page set"

Hi Vivek,

Thanks for your ack.

在 2025/4/22 13:14, Kasireddy, Vivek 写道:
> Hi Huan,
>
>> Subject: [PATCH 1/2] Revert "udmabuf: fix vmap_udmabuf error page set"
>>
>> This reverts commit 18d7de823b7150344d242c3677e65d68c5271b04.
>>
>> This given a misuse of vmap_pfn, vmap_pfn only allow none-page based
>> user invoke, i.e. PCIe BARs and other.
> The commit message can be improved a little bit to briefly explain why vmap_pfn()
> would not work for this use-case.

OK, I will update patch direct in later reply.:)

Thanks,

Huan

>
> Acked-by: Vivek Kasireddy <vivek.kasireddy@...el.com>
>
> Thanks,
> Vivek
>
>> Signed-off-by: Huan Yang <link@...o.com>
>> Reported-by: Bingbu Cao <bingbu.cao@...ux.intel.com>
>> Closes: https://lore.kernel.org/dri-devel/eb7e0137-3508-4287-98c4-
>> 816c5fd98e10@...o.com/T/#mbda4f64a3532b32e061f4e8763bc8e307bea3ca
>> 8
>> ---
>>   drivers/dma-buf/Kconfig   |  1 -
>>   drivers/dma-buf/udmabuf.c | 22 +++++++---------------
>>   2 files changed, 7 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig
>> index fee04fdb0822..b46eb8a552d7 100644
>> --- a/drivers/dma-buf/Kconfig
>> +++ b/drivers/dma-buf/Kconfig
>> @@ -36,7 +36,6 @@ config UDMABUF
>>   	depends on DMA_SHARED_BUFFER
>>   	depends on MEMFD_CREATE || COMPILE_TEST
>>   	depends on MMU
>> -	select VMAP_PFN
>>   	help
>>   	  A driver to let userspace turn memfd regions into dma-bufs.
>>   	  Qemu can use this to create host dmabufs for guest framebuffers.
>> diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
>> index 7eee3eb47a8e..79845565089d 100644
>> --- a/drivers/dma-buf/udmabuf.c
>> +++ b/drivers/dma-buf/udmabuf.c
>> @@ -109,29 +109,21 @@ static int mmap_udmabuf(struct dma_buf *buf,
>> struct vm_area_struct *vma)
>>   static int vmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
>>   {
>>   	struct udmabuf *ubuf = buf->priv;
>> -	unsigned long *pfns;
>> +	struct page **pages;
>>   	void *vaddr;
>>   	pgoff_t pg;
>>
>>   	dma_resv_assert_held(buf->resv);
>>
>> -	/**
>> -	 * HVO may free tail pages, so just use pfn to map each folio
>> -	 * into vmalloc area.
>> -	 */
>> -	pfns = kvmalloc_array(ubuf->pagecount, sizeof(*pfns), GFP_KERNEL);
>> -	if (!pfns)
>> +	pages = kvmalloc_array(ubuf->pagecount, sizeof(*pages),
>> GFP_KERNEL);
>> +	if (!pages)
>>   		return -ENOMEM;
>>
>> -	for (pg = 0; pg < ubuf->pagecount; pg++) {
>> -		unsigned long pfn = folio_pfn(ubuf->folios[pg]);
>> -
>> -		pfn += ubuf->offsets[pg] >> PAGE_SHIFT;
>> -		pfns[pg] = pfn;
>> -	}
>> +	for (pg = 0; pg < ubuf->pagecount; pg++)
>> +		pages[pg] = &ubuf->folios[pg]->page;
>>
>> -	vaddr = vmap_pfn(pfns, ubuf->pagecount, PAGE_KERNEL);
>> -	kvfree(pfns);
>> +	vaddr = vm_map_ram(pages, ubuf->pagecount, -1);
>> +	kvfree(pages);
>>   	if (!vaddr)
>>   		return -EINVAL;
>>
>> --
>> 2.48.1