* [bug report] video: hyperv: hyperv_fb: Use physical memory for fb on HyperV Gen 1 VMs.
@ 2020-02-05 5:43 Dan Carpenter
2020-02-05 7:21 ` Wei Hu
0 siblings, 1 reply; 4+ messages in thread
From: Dan Carpenter @ 2020-02-05 5:43 UTC (permalink / raw)
To: weh; +Cc: linux-hyperv
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.
992 }
993
994 return paddr;
995 }
regards,
dan carpenter
^ permalink raw reply [flat|nested] 4+ messages in thread* RE: [bug report] video: hyperv: hyperv_fb: Use physical memory for fb on HyperV Gen 1 VMs.
2020-02-05 5:43 [bug report] video: hyperv: hyperv_fb: Use physical memory for fb on HyperV Gen 1 VMs Dan Carpenter
@ 2020-02-05 7:21 ` Wei Hu
2020-02-05 8:07 ` Dan Carpenter
0 siblings, 1 reply; 4+ messages in thread
From: Wei Hu @ 2020-02-05 7:21 UTC (permalink / raw)
To: Dan Carpenter; +Cc: linux-hyperv
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.
Thanks,
Wei
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [bug report] video: hyperv: hyperv_fb: Use physical memory for fb on HyperV Gen 1 VMs.
2020-02-05 7:21 ` Wei Hu
@ 2020-02-05 8:07 ` Dan Carpenter
2020-02-05 11:33 ` Wei Hu
0 siblings, 1 reply; 4+ messages in thread
From: Dan Carpenter @ 2020-02-05 8:07 UTC (permalink / raw)
To: Wei Hu; +Cc: linux-hyperv
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
^ permalink raw reply [flat|nested] 4+ messages in thread* RE: [bug report] video: hyperv: hyperv_fb: Use physical memory for fb on HyperV Gen 1 VMs.
2020-02-05 8:07 ` Dan Carpenter
@ 2020-02-05 11:33 ` Wei Hu
0 siblings, 0 replies; 4+ messages in thread
From: Wei Hu @ 2020-02-05 11:33 UTC (permalink / raw)
To: Dan Carpenter; +Cc: linux-hyperv
> -----Original Message-----
> > 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://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Flkml.or
> g%2Flkml%2F2019%2F6%2F17%2F155&data=02%7C01%7Cweh%40micro
> soft.com%7Cff5687dc7bb648623d3708d7aa127a4b%7C72f988bf86f141af91a
> b2d7cd011db47%7C1%7C0%7C637164868648450097&sdata=0%2B8Jwe
> 1A%2FtOW0LqF8t2hqymWuzZjVtUxBIKgMyOQdFc%3D&reserved=0
>
I see. This is virtual frame buffer device on Hyper-V. It would not get address from
vmap or ioremap. On the other hand, if dma_alloc_coherent() returns address without
page backing, this driver will blow even without calling virt_to_phys.
Dma_alloc_coherent() is the recommended interface to allocate large contiguous
physical memory, in which case this call is doing so. I think you can ignore this
in your check.
Thanks,
Wei
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-02-05 11:33 UTC | newest]
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2020-02-05 5:43 [bug report] video: hyperv: hyperv_fb: Use physical memory for fb on HyperV Gen 1 VMs Dan Carpenter
2020-02-05 7:21 ` Wei Hu
2020-02-05 8:07 ` Dan Carpenter
2020-02-05 11:33 ` Wei Hu
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