On Sun, Jul 8, 2012 at 4:56 PM, Andy Walls <[email protected]> wrote: > On Sun, 2012-07-08 at 15:28 -0400, Andy Walls wrote: >> On Sat, 2012-07-07 at 12:44 -0500, Robert Rust wrote: >> > After weeks of headaches trying to get my HVR-1600 to work, I finally >> > determined with help from this list that the H77 chipset on my >> > motherboard was the root of my problems, so I replaced the board. I >> > am now trying to set up my MythTV backend in a Xen domU after >> > verifying that it can capture outside of Xen and in the Xen dom0 host. >> >> What is the difference between Xen domain dom0 and domU (for a Xen newb >> like me)? >> >> > > Ah, found it: > http://wiki.xen.org/wiki/XenOverview#Introduction_to_Xen_Architecture > > "... Domain 0) is a specialized Virtual Machine that 0 has special > privileges like the capability to access the hardware directly, handles > all access to the system’s I/O functions ..." > > "... Xen [domU] guests are totally isolated from the hardware: in other > words, they have no privilege to access hardware or I/O functionality. > Thus, they are also called unprivileged domain (or DomU)." > >> > I can tune to channels and I get data when I cat /dev/video0 ... but >> > the data doesn't seem to be valid video. > > >> > Does anybody have input on how I can work towards a resolution on >> > this? > > This page looks helpful: > > http://wiki.xen.org/wiki/XenPCIpassthrough > > If your linux kernel panics because the cx18 driver asks for more DMA > buffer space than the SWIOTLB (Software IOMMU) in Linux can provide, you > can cut down on the number and size of buffers for CX23418 data streams > using cx18 module options. > > Also the Linux Software IOMMU requires copies of DMA buffres by the CPU, > so performance will stink, unless you have lots of excess horsepower. > > Please note that the CX23418 acts as a DMA master on the PCI bus. When > the cx18 driver tells the CX23418 about where the DMA buffers are, they > must be the correct PCI address-space addresses that the CX23418 chip > and firmware can actually DMA into. If you have a Linux kernel running > in any other Xen (dom0 or domU) guest, you should probably blacklist the > cx18 driver in that guest, so that instance of the cx18 driver doesn't > also load the CX23418 with DMA addresses to use or otherwise change the > CX23418's System Control Block (SCB) area. > > (In case you are interested, this is the function in the cx18 driver > where the driver tells the firmware about the DMA addresses of buffers: > > http://git.linuxtv.org/media_tree.git/blob/staging/for_v3.6:/drivers/media/video/cx18/cx18-queue.c#l277 > > and this is the function that initializes the SCB on driver probe: > > http://git.linuxtv.org/media_tree.git/blob/staging/for_v3.6:/drivers/media/video/cx18/cx18-scb.c#l27 > ) >
Would this preclude passing a second HVR-1600 to a different DomU ? DomU #2 sees the HVR-1600 and loads the cx18 module for it, but I can't capture valid video. If you're wondering why I don't pass it to DomU #1 (in which the first HVR-1600 works fine), I can't seem to get DomU #1 to see both cards at once. In DomU #2, I get messages like the following: Sep 23 16:23:59 merry kernel: [ 1131.227956] cx18-0: Skipped encoder MPEG, MDL 9, 62 times - it must have dropped out of rotation Thoughts? I'm also going to try pursuing why I can't pass both cards to one DomU. -Robert _______________________________________________ ivtv-users mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-users
