Hi,
I allocate a big chunck of memory from user space with :
#define MEM_SIZE_DMA (128*1024*1024)
// allocate 128MB of memory
void *_pVirtualMem = memalign(sysconf(_SC_PAGESIZE), MEM_SIZE_DMA);
// Reserve memory
memset(_pVirtualMem, 0, MEM_SIZE_DMA);
// Lock memory
if (!mlock(_pVirtualMem, MEM_SIZE_DMA ))
{
free(_pVirtualMem);
return false;
}
Then I call an IOCTL from my driver (DmaMapDescrpImg) to create a DMA
scatter gather list.
This solution works when I have 1GB of memory. If I put 2GB of memory,
it won't work because I can't resolve the physical address of my User
memory area.
My configuration is a Redhat enterprise 3.3 SMP on Xeon 3.2GHz.
The kernel is configured for 64GB support.
So the kernel only have access to LOW part of memory.
How can I force my User allocation in LOW part, or how can I replace
map_user_from_kiobuf() to support this memory ?
With kiobuf, I make DMA scatter gather list at the opening of the card
and then I use it to perform DMA transfer. With get_user_pages(), I must
make a scatter gather list for each transfer, and make pages dirty after
each transfer ?
I am not sure that get_user_pages() is the good solution.
Is there another method to perform my DMA transfer.
I must allocate my memory in user space, and I can't copy it from kernel
to user because I'll have a big overhead.
Regards.
Sebastien
Kernel IOCTL :
int DmaMapDescrpImg (int board_num, u32 arg)
{
struct kiobuf *iobuf;
// get parameters
get_user ( ... );
// Create kiovec into decriptor pointer registers
// Map kiovec into descriptor pointer register
result = alloc_kiovec(1, &iobuf);
if (result)
{
TRACE_ERR("alloc_kiovec failed\n");
return 1;
}
result = map_user_kiobuf(READ,
iobuf, // struct kiobuf
arg, // user addr (buffer passed from user)
iSize);// size
if (result)
{
TRACE_ERR("map_user_kiobuf failed\n");
free_kiovec(1, &iobuf);
return 1;
}
// ************************* Build descriptors
transfer = &(pdx[board_num].ReadTransfer);
// Number of descriptor needed
nbDescrpImg = iSize/PAGE_SIZE + ((iSize%PAGE_SIZE) ? 1 : 0);
// Index of the first descriptor in transfer->Descript[]
idxDescrpImg = nImage * nbDescrpImg;
transfer->image[nImage].Descript = &(transfer->Descript[idxDescrpImg]);
transfer->imageInfo->flag[nImage] = IMG_UNUSED; //IMG_UNLOCK;
for(i=idxDescrpImg, idxIobuf = 0 ; i < idxDescrpImg + nbDescrpImg - 1
; i++, idxIobuf++)
{
transfer->Descript[i].size = PAGE_SIZE;
transfer->Descript[i].pciaddr = (ULONG)
virt_to_phys(page_address(iobuf->maplist[idxIobuf]));
transfer->Descript[i].localaddr = localaddr;
transfer->Descript[i].next = (ULONG)
virt_to_phys(&(transfer->Descript[i+1])) | PLX_PCI | PLX_READ;
}
// End Of Chain
transfer->Descript[i].size = PAGE_SIZE;
transfer->Descript[i].pciaddr = (ULONG)
virt_to_phys(page_address(iobuf->maplist[idxIobuf]));
transfer->Descript[i].localaddr = localaddr;
transfer->Descript[i].next = PLX_PCI | (bRead ? PLX_READ :
PLX_WRITE)
| PLX_EOC;
// ******************************************
// unmap and free kiobuf
unmap_kiobuf(iobuf);
free_kiovec(1, &iobuf);
return 0;
}
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