Il 09/08/2016 00:21, Luca dariz ha scritto: > Il 30/07/2016 03:47, Olaf Buddenhagen ha scritto: >> On Fri, Jul 29, 2016 at 06:30:09PM +0000, Luca wrote: >> >>> I need a way to translate logical addresses to physical, >> >> Is this for DMA or something along these lines? If so, the interface for >> allocating "contiguous memory" that was added for the purpose of DDE >> should work here as well I'd presume. >> >> (I didn't like how the original interface was designed specifically, and >> I don't know whether in has been improved since -- but regardless, it >> should get the job done...) >> >> If it doesn't cut it, or this is about something else entirely, could >> you elaborate please? >> > > The contiguous memory allocation interface is not enough. I mean, at > least in the virtio ld driver, there are some addresses that must be > translated which are not allocated with vm_allocate_contiguous. However > I did not investigate in detail why this is needed.
I investigated a bit more, and it seems that these addresses correspond to buffers in the netbsd block cache, so this is the reason for not being allocated with vm_allocate_contiguous().. Also these buffers are used to read and write data. I think the virtio driver uses DMA however I can read and write to the underlying device apparently without problems.. Here's a simple test to show what I'm doing: uint8_t *buf=malloc(size); memset(buf, 0x5a, size); fd = rump_sys_open(("/dev/ld0d", RUMP_O_RDWR); rump_sys_write(fd, buf, size); rump_sys_lseek(fd, 0, SEEK_SET); memset(buf, 0, size); rump_sys_read(fd, buf, size); ... check that I read the same that I wrote ... rump_sys-close(fd); Could it be that I'm just lucky to not have a page boundary in the middle of a block cache buffer? I'd expect to see some hole reading back the data.. Cheers Luca
Description: OpenPGP digital signature