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accel/amdxdna: Support read-only user-pointer BO mappings

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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.

Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Max Zhen <max.zhen@amd.com>
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Link: https://patch.msgid.link/20260331172635.3275296-1-lizhi.hou@amd.com
This commit is contained in:
Max Zhen 2026-03-31 10:26:35 -07:00 committed by Lizhi Hou
parent 43c9a66ea1
commit f649e63d4a
1 changed files with 27 additions and 2 deletions
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29
drivers/accel/amdxdna/amdxdna_ubuf.c
View File

@ -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)) {