I wonder, then, what the correct service is to get the cpu physical
address from a kernel virtual address returned from
dma_alloc_coherent()? I think this is correct as-is, since I think
dma_alloc_coherent() falls under the "directly mapped" addresses in the
virt_to_phys() prototype comment.
What do you think Roland?
On 1/30/2013 3:00 PM, Dan Carpenter wrote:
Hello Steve Wise,
The patch c6d7b26791a2: "RDMA/cxgb4: Support on-chip SQs" from Sep
13, 2010, leads to the following warning:
"drivers/infiniband/hw/cxgb4/qp.c:98 alloc_host_sq()
error: 'sq->queue' came from dma_alloc_coherent() so we can't
do virt_to_phys()"
drivers/infiniband/hw/cxgb4/qp.c
92 static int alloc_host_sq(struct c4iw_rdev *rdev, struct t4_sq *sq)
93 {
94 sq->queue = dma_alloc_coherent(&(rdev->lldi.pdev->dev),
sq->memsize,
95 &(sq->dma_addr), GFP_KERNEL);
96 if (!sq->queue)
97 return -ENOMEM;
98 sq->phys_addr = virt_to_phys(sq->queue);
99 pci_unmap_addr_set(sq, mapping, sq->dma_addr);
100 return 0;
101 }
This is a new Smatch check. I don't know the rules on virt_to_phys yet
but here is the relevant comment.
/**
* virt_to_phys - map virtual addresses to physical
* @address: address to remap
*
* The returned physical address is the physical (CPU) mapping for
* the memory address given. It is only valid to use this function on
* addresses directly mapped or allocated via kmalloc.
*
* This function does not give bus mappings for DMA transfers. In
* almost all conceivable cases a device driver should not be using
* this function
*/
regards,
dan carpenter
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