On Wed, Sep 19, 2012 at 2:32 PM, Edgar E. Iglesias <edgar.igles...@gmail.com> wrote: > On Wed, Sep 19, 2012 at 02:25:48PM +1000, Peter Crosthwaite wrote: >> Ping for PMM, >> >> This is the root case of your block on the SDHCI series - this is a >> discussion on resolution to bogus infinite looping DMA. For current >> participants in this discussion, heres our thread on the same topic >> over in SD land: >> >> http://lists.gnu.org/archive/html/qemu-devel/2012-08/msg01017.html >> >> With the findings here and acknowledgement that this is a general >> problem, we either need to declare this issue of scope for SDHCI, or >> work with these guys (in the immediate future) on the DMA infinite >> loop problem flagged here. I dont mind if SDHCI+ADMA is the guinea pig >> here, but can we get a decisive plan for going forward with this issue >> if it is going to continue to block SDHCI. >> >> Thanks to Igor for identifying the overlap between these discussions. > > Hi, > > A couple of dumb questions. > > What is the reason for the blocker? that possible guest dos is worse > than no functionality at all? > > Can't you put the DMA/IO processing into the background?
I dont know a way do do asynchronous DMA unless I am missing something here. So what happens is we have a device that walks a SG list synchronously while holding all the locks and stuff being discussed here. If that SG list infinite loops then crash. > > what's the diff between setup of bad descriptors and writing a > while (1) loop in the guest CPU? > While(1) in guest doesnt freeze all of QEMU (monitor still works and stuff), wheras the DMA ops going in circles does, as locks are taken by an infinite loop. Regards, peter > Cheers, > E
