Hi Wei Liu,
Please do not pick up this patch, because actually MMIO VRAM can not work
with fb_deferred_io.
Previously I didn't test Xorg -- sorry. As soon as I tested it, I got the below
warning and the Xorg program ternimated immediately:
[ 28.148432] WARNING: CPU: 19 PID: 1410 at mm/vmalloc.c:383 vmalloc_to_page+0x14b/0x150
...
[ 28.192959] CPU: 19 PID: 1410 Comm: Xorg Tainted: G E 5.10.0-rc1+ #4
...
[ 28.208720] RIP: 0010:vmalloc_to_page+0x14b/0x150
...
[ 28.299231] Call Trace:
[ 28.301428] fb_deferred_io_fault+0x3a/0xa0
[ 28.305276] __do_fault+0x36/0x120
[ 28.308276] handle_mm_fault+0x1144/0x1950
[ 28.311963] exc_page_fault+0x290/0x510
[ 28.315551] ? asm_exc_page_fault+0x8/0x30
[ 28.319186] asm_exc_page_fault+0x1e/0x30
[ 28.322969] RIP: 0033:0x7fbeda3ec2f5
The issue is that fb_deferred_io_page() requires that the PFN be backed by a
struct page, but it looks the MMIO address does not have the struct page backed.
So I have to drop this patch.
Thanks Wei Hu and Michael for pointing this out!
FYI: drivers/video/fbdev/core/fb_defio.c:
static struct page *fb_deferred_io_page(struct fb_info *info, unsigned long offs)
{
void *screen_base = (void __force *) info->screen_base;
struct page *page;
if (is_vmalloc_addr(screen_base + offs))
page = vmalloc_to_page(screen_base + offs);
else
page = pfn_to_page((info->fix.smem_start + offs) >> PAGE_SHIFT);
return page;
}
/* this is to find and return the vmalloc-ed fb pages */
static vm_fault_t fb_deferred_io_fault(struct vm_fault *vmf)
{
unsigned long offset;
struct page *page;
struct fb_info *info = vmf->vma->vm_private_data;
offset = vmf->pgoff << PAGE_SHIFT;
if (offset >= info->fix.smem_len)
return VM_FAULT_SIGBUS;
page = fb_deferred_io_page(info, offset);
if (!page)
return VM_FAULT_SIGBUS;
Thanks,
-- Dexuan
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