On 3/31/26 12:26, Lizhi Hou wrote:
From: Max Zhen <[email protected]> Update the amdxdna user-pointer (ubuf) BO path to support creating buffer objects from read-only user mappings. Detect read-only VMAs by checking VMA permissions across all user virtual address ranges associated with the BO. When all entries are read-only, pin user pages without FOLL_WRITE and export the resulting dmabuf as read-only (O_RDONLY). This allows userptr BOs backed by read-only mappings to be safely imported and used without requiring write access, which was previously rejected due to unconditional FOLL_WRITE usage. Signed-off-by: Max Zhen <[email protected]> Signed-off-by: Lizhi Hou <[email protected]> --- drivers/accel/amdxdna/amdxdna_ubuf.c | 29 ++++++++++++++++++++++++++-- 1 file changed, 27 insertions(+), 2 deletions(-)
Reviewed-by: Mario Limonciello (AMD) <[email protected]>
diff --git a/drivers/accel/amdxdna/amdxdna_ubuf.c b/drivers/accel/amdxdna/amdxdna_ubuf.c index 4c0647057759..3769210c55cc 100644 --- a/drivers/accel/amdxdna/amdxdna_ubuf.c +++ b/drivers/accel/amdxdna/amdxdna_ubuf.c @@ -125,6 +125,26 @@ static const struct dma_buf_ops amdxdna_ubuf_dmabuf_ops = { .vunmap = amdxdna_ubuf_vunmap, };+static int readonly_va_entry(struct amdxdna_drm_va_entry *va_ent)+{ + struct mm_struct *mm = current->mm; + struct vm_area_struct *vma; + int ret; + + mmap_read_lock(mm); + + vma = find_vma(mm, va_ent->vaddr); + if (!vma || + vma->vm_start > va_ent->vaddr || + vma->vm_end - va_ent->vaddr < va_ent->len) + ret = -ENOENT; + else + ret = vma->vm_flags & VM_WRITE ? 0 : 1; + + mmap_read_unlock(mm); + return ret; +} + struct dma_buf *amdxdna_get_ubuf(struct drm_device *dev, u32 num_entries, void __user *va_entries) { @@ -134,6 +154,7 @@ struct dma_buf *amdxdna_get_ubuf(struct drm_device *dev, struct amdxdna_ubuf_priv *ubuf; u32 npages, start = 0; struct dma_buf *dbuf; + bool readonly = true; int i, ret; DEFINE_DMA_BUF_EXPORT_INFO(exp_info);@@ -172,6 +193,10 @@ struct dma_buf *amdxdna_get_ubuf(struct drm_device *dev,ret = -EINVAL; goto free_ent; } + + /* Pin pages as writable as long as not all entries are read-only. */ + if (readonly && readonly_va_entry(&va_ent[i]) != 1) + readonly = false; }ubuf->nr_pages = exp_info.size >> PAGE_SHIFT;@@ -194,7 +219,7 @@ struct dma_buf *amdxdna_get_ubuf(struct drm_device *dev, npages = va_ent[i].len >> PAGE_SHIFT;ret = pin_user_pages_fast(va_ent[i].vaddr, npages,- FOLL_WRITE | FOLL_LONGTERM, + (readonly ? 0 : FOLL_WRITE) | FOLL_LONGTERM, &ubuf->pages[start]); if (ret >= 0) { start += ret; @@ -211,7 +236,7 @@ struct dma_buf *amdxdna_get_ubuf(struct drm_device *dev,exp_info.ops = &amdxdna_ubuf_dmabuf_ops;exp_info.priv = ubuf; - exp_info.flags = O_RDWR | O_CLOEXEC; + exp_info.flags = (readonly ? O_RDONLY : O_RDWR) | O_CLOEXEC;dbuf = dma_buf_export(&exp_info);if (IS_ERR(dbuf)) {
