diff mbox series

[v6,3/7] udmabuf: fix vmap_udmabuf error page set

Message ID 20240909091851.1165742-4-link@vivo.com (mailing list archive)
State New, archived
Headers show
Series udmabuf bug fix and some improvements | expand

Commit Message

Huan Yang Sept. 9, 2024, 9:18 a.m. UTC 
Currently vmap_udmabuf set page's array by each folio.
But, ubuf->folios is only contain's the folio's head page.

That mean we repeatedly mapped the folio head page to the vmalloc area.

Due to udmabuf can use hugetlb, if HVO enabled, tail page may not exist,
so, we can't use page array to map, instead, use pfn array.

By this, we removed page usage in udmabuf totally.

Suggested-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Signed-off-by: Huan Yang <link@vivo.com>
Acked-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
---
 drivers/dma-buf/Kconfig   |  1 +
 drivers/dma-buf/udmabuf.c | 22 +++++++++++++++-------
 2 files changed, 16 insertions(+), 7 deletions(-)

Comments

Kasireddy, Vivek Sept. 12, 2024, 10:37 p.m. UTC | #1 
Hi Huan,

> Subject: [PATCH v6 3/7] udmabuf: fix vmap_udmabuf error page set
> 
> Currently vmap_udmabuf set page's array by each folio.
> But, ubuf->folios is only contain's the folio's head page.
> 
> That mean we repeatedly mapped the folio head page to the vmalloc area.
> 
> Due to udmabuf can use hugetlb, if HVO enabled, tail page may not exist,
> so, we can't use page array to map, instead, use pfn array.
> 
> By this, we removed page usage in udmabuf totally.
> 
I think this would probably need a Fixes tag:
Fixes: 5e72b2b41a21 ("udmabuf: convert udmabuf driver to use folios")

Thanks,
Vivek

> Suggested-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
> Signed-off-by: Huan Yang <link@vivo.com>
> Acked-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
> ---
>  drivers/dma-buf/Kconfig   |  1 +
>  drivers/dma-buf/udmabuf.c | 22 +++++++++++++++-------
>  2 files changed, 16 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig
> index b46eb8a552d7..fee04fdb0822 100644
> --- a/drivers/dma-buf/Kconfig
> +++ b/drivers/dma-buf/Kconfig
> @@ -36,6 +36,7 @@ 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 ba9dbc7caf71..aa182a9dcdfa 100644
> --- a/drivers/dma-buf/udmabuf.c
> +++ b/drivers/dma-buf/udmabuf.c
> @@ -103,21 +103,29 @@ 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;
> -	struct page **pages;
> +	unsigned long *pfns;
>  	void *vaddr;
>  	pgoff_t pg;
> 
>  	dma_resv_assert_held(buf->resv);
> 
> -	pages = kvmalloc_array(ubuf->pagecount, sizeof(*pages),
> GFP_KERNEL);
> -	if (!pages)
> +	/**
> +	 * 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)
>  		return -ENOMEM;
> 
> -	for (pg = 0; pg < ubuf->pagecount; pg++)
> -		pages[pg] = &ubuf->folios[pg]->page;
> +	for (pg = 0; pg < ubuf->pagecount; pg++) {
> +		unsigned long pfn = folio_pfn(ubuf->folios[pg]);
> 
> -	vaddr = vm_map_ram(pages, ubuf->pagecount, -1);
> -	kvfree(pages);
> +		pfn += ubuf->offsets[pg] >> PAGE_SHIFT;
> +		pfns[pg] = pfn;
> +	}
> +
> +	vaddr = vmap_pfn(pfns, ubuf->pagecount, PAGE_KERNEL);
> +	kvfree(pfns);
>  	if (!vaddr)
>  		return -EINVAL;
> 
> --
> 2.45.2
Huan Yang Sept. 13, 2024, 6:31 a.m. UTC | #2 
在 2024/9/13 6:37, Kasireddy, Vivek 写道:
> Hi Huan,
>
>> Subject: [PATCH v6 3/7] udmabuf: fix vmap_udmabuf error page set
>>
>> Currently vmap_udmabuf set page's array by each folio.
>> But, ubuf->folios is only contain's the folio's head page.
>>
>> That mean we repeatedly mapped the folio head page to the vmalloc area.
>>
>> Due to udmabuf can use hugetlb, if HVO enabled, tail page may not exist,
>> so, we can't use page array to map, instead, use pfn array.
>>
>> By this, we removed page usage in udmabuf totally.
>>
> I think this would probably need a Fixes tag:
> Fixes: 5e72b2b41a21 ("udmabuf: convert udmabuf driver to use folios")
OK, I'll update it
>
> Thanks,
> Vivek
>
>> Suggested-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
>> Signed-off-by: Huan Yang <link@vivo.com>
>> Acked-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
>> ---
>>   drivers/dma-buf/Kconfig   |  1 +
>>   drivers/dma-buf/udmabuf.c | 22 +++++++++++++++-------
>>   2 files changed, 16 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig
>> index b46eb8a552d7..fee04fdb0822 100644
>> --- a/drivers/dma-buf/Kconfig
>> +++ b/drivers/dma-buf/Kconfig
>> @@ -36,6 +36,7 @@ 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 ba9dbc7caf71..aa182a9dcdfa 100644
>> --- a/drivers/dma-buf/udmabuf.c
>> +++ b/drivers/dma-buf/udmabuf.c
>> @@ -103,21 +103,29 @@ 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;
>> -	struct page **pages;
>> +	unsigned long *pfns;
>>   	void *vaddr;
>>   	pgoff_t pg;
>>
>>   	dma_resv_assert_held(buf->resv);
>>
>> -	pages = kvmalloc_array(ubuf->pagecount, sizeof(*pages),
>> GFP_KERNEL);
>> -	if (!pages)
>> +	/**
>> +	 * 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)
>>   		return -ENOMEM;
>>
>> -	for (pg = 0; pg < ubuf->pagecount; pg++)
>> -		pages[pg] = &ubuf->folios[pg]->page;
>> +	for (pg = 0; pg < ubuf->pagecount; pg++) {
>> +		unsigned long pfn = folio_pfn(ubuf->folios[pg]);
>>
>> -	vaddr = vm_map_ram(pages, ubuf->pagecount, -1);
>> -	kvfree(pages);
>> +		pfn += ubuf->offsets[pg] >> PAGE_SHIFT;
>> +		pfns[pg] = pfn;
>> +	}
>> +
>> +	vaddr = vmap_pfn(pfns, ubuf->pagecount, PAGE_KERNEL);
>> +	kvfree(pfns);
>>   	if (!vaddr)
>>   		return -EINVAL;
>>
>> --
>> 2.45.2
diff mbox series

Patch

diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig
index b46eb8a552d7..fee04fdb0822 100644
--- a/drivers/dma-buf/Kconfig
+++ b/drivers/dma-buf/Kconfig
@@ -36,6 +36,7 @@  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 ba9dbc7caf71..aa182a9dcdfa 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -103,21 +103,29 @@  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;
-	struct page **pages;
+	unsigned long *pfns;
 	void *vaddr;
 	pgoff_t pg;
 
 	dma_resv_assert_held(buf->resv);
 
-	pages = kvmalloc_array(ubuf->pagecount, sizeof(*pages), GFP_KERNEL);
-	if (!pages)
+	/**
+	 * 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)
 		return -ENOMEM;
 
-	for (pg = 0; pg < ubuf->pagecount; pg++)
-		pages[pg] = &ubuf->folios[pg]->page;
+	for (pg = 0; pg < ubuf->pagecount; pg++) {
+		unsigned long pfn = folio_pfn(ubuf->folios[pg]);
 
-	vaddr = vm_map_ram(pages, ubuf->pagecount, -1);
-	kvfree(pages);
+		pfn += ubuf->offsets[pg] >> PAGE_SHIFT;
+		pfns[pg] = pfn;
+	}
+
+	vaddr = vmap_pfn(pfns, ubuf->pagecount, PAGE_KERNEL);
+	kvfree(pfns);
 	if (!vaddr)
 		return -EINVAL;