On 01.07.2011, at 16:59, Fabien Chouteau wrote: > On 01/07/2011 00:38, Alexander Graf wrote: >> >> On 01.07.2011, at 00:32, Scott Wood wrote: >> >>> On Fri, 1 Jul 2011 00:28:19 +0200 >>> Alexander Graf <ag...@suse.de> wrote: >>> >>>> >>>> On 01.07.2011, at 00:23, Scott Wood wrote: >>>> >>>>> On Fri, 1 Jul 2011 00:18:22 +0200 >>>>> Alexander Graf <ag...@suse.de> wrote: >>>>> >>>>>> >>>>>> On 01.07.2011, at 00:11, Scott Wood wrote: >>>>>> >>>>>>> Almost, but what if we have write permission but not read? >>>>>> >>>>>> How would you write back data from a cache line when you haven't read it >>>>>> earlier? >>>>> >>>>> The CPU can read it. The program can't. >>>> >>>> Hrm. We can always just call the check manually and trigger the respective >>>> interrupt :). >>> >>> Yep. A little trickier, but doable. >>> >>>>>>> but what about a race with DMA from the I/O thread? >>>>>> >>>>>> That'd simply be broken, but I don't quite see how it wouldn't with real >>>>>> hardware either :). >>>>> >>>>> Real hardware doesn't generate a load/store sequence that the program >>>>> didn't >>>>> ask for -- where's the breakage? >>>> >>>> Real hardware flushes whatever contents are in that cache line to RAM, no? >>>> So it would collide with the DMA just as much. Or am I missing something? >>> >>> If the DMA happens after the cache line is fetched, it'll be flushed, >>> whether locked or not. But that's different from losing some of what the >>> device wrote. >> >> Ah, so DMA flushes even locked cache lines? Then it makes sense. Well, I >> guess the best choice here really is to merely do a manual storage >> protection check and be done with it. >> > > Well, this is far beyond the scope of my knowledge of e500 and the current > patch is sufficient for me, so I will let you implement this if you want to...
Well, all it needs is to call mmubooke206_get_physical_address on the address (or each page of the destination) with access_type set to write and check for the result. If it's protected, inject a DSI (see cpu_ppc_handle_mmu_fault). But yeah, I can try and see if I get around to implementing it. No promises though. Do you have a test case I can verify this against? Alex
