Re: [PATCH 1/2] Revert "udmabuf: fix vmap_udmabuf error page set"

[Huan Yang]

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.kasire...@intel.com>

Thanks,
Vivek

Signed-off-by: Huan Yang <l...@vivo.com>
Reported-by: Bingbu Cao <bingbu....@linux.intel.com>
Closes: https://lore.kernel.org/dri-devel/eb7e0137-3508-4287-98c4-
816c5fd98...@vivo.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