On Wed, Feb 05, 2020 at 07:21:31AM +0000, Wei Hu wrote:
> Hello Dan,
>
> > -----Original Message----->
> > Hello Wei Hu,
> >
> > The patch 3a6fb6c4255c: "video: hyperv: hyperv_fb: Use physical memory for
> > fb on HyperV Gen 1 VMs." from Dec 9, 2019, leads to the following static
> > checker warning:
> >
> > drivers/video/fbdev/hyperv_fb.c:991 hvfb_get_phymem()
> > error: 'vmem' came from dma_alloc_coherent() so we can't do
> > virt_to_phys()
> >
> > drivers/video/fbdev/hyperv_fb.c
> > 960 static phys_addr_t hvfb_get_phymem(struct hv_device *hdev,
> > 961 unsigned int request_size)
> > 962 {
> > 963 struct page *page = NULL;
> > 964 dma_addr_t dma_handle;
> > 965 void *vmem;
> > 966 phys_addr_t paddr = 0;
> > 967 unsigned int order = get_order(request_size);
> > 968
> > 969 if (request_size == 0)
> > 970 return -1;
> > 971
> > 972 if (order < MAX_ORDER) {
> > 973 /* Call alloc_pages if the size is less than 2^MAX_ORDER */
> > 974 page = alloc_pages(GFP_KERNEL | __GFP_ZERO, order);
> > 975 if (!page)
> > 976 return -1;
> > 977
> > 978 paddr = (page_to_pfn(page) << PAGE_SHIFT);
> > 979 } else {
> > 980 /* Allocate from CMA */
> > 981 hdev->device.coherent_dma_mask = DMA_BIT_MASK(64);
> > 982
> > 983 vmem = dma_alloc_coherent(&hdev->device,
> > 984 round_up(request_size, PAGE_SIZE),
> > 985 &dma_handle,
> > 986 GFP_KERNEL | __GFP_NOWARN);
> > 987
> > 988 if (!vmem)
> > 989 return -1;
> > 990
> > 991 paddr = virt_to_phys(vmem);
> >
> > Pretty straight forward that the static checker is right but I can't give you any
> > hints how to fix it.
> >
>
> Thanks for reporting this. Would you let me know how I can reproduce this warning or
> Error message? The build on my side runs fine without such message.
Hm... Sorry, I never publish this Smatch check. I should do that.
Anyway HCH explains the rules a bit in this email:
https://lkml.org/lkml/2019/6/17/155
regards,
dan carpenter
