Hi Huan, > Subject: Re: [PATCH 1/2] Revert "udmabuf: fix vmap_udmabuf error page set" > > From 38aa11d92f209e7529736f3e11e08dfc804bdfae Mon Sep 17 00:00:00 > 2001 > From: Huan Yang <l...@vivo.com> > Date: Tue, 15 Apr 2025 10:04:18 +0800 > 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 give a !pfn_valid check > to avoid user miss use it. This API design to only for none-page struct > based user invoke, i.e. PCIe BARs and other. So any page based will > inject by !pfn_valid check. > > udmabuf used shmem or hugetlb as folio src, hence, page/folio based, > can't use it. Please consider having a commit message like below and resend both patches: "We cannot use vmap_pfn() in vmap_udmabuf() as it would fail the pfn_valid() check in vmap_pfn_apply(). This is because vmap_pfn() is intended to be used for mapping non-struct-page memory such as PCIe BARs. Since, udmabuf mostly works with pages/folios backed by shmem/hugetlbfs/THP, vmap_pfn() is not the right tool or API to invoke for implementing vmap."
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 > Acked-by: Vivek Kasireddy <vivek.kasire...@intel.com> > --- > 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 >
