On Apr 28, 2005, at 4:11 PM, Christian Gan wrote:
Could this also related to this problem I posted a long time ago? I haven't had a chance to revisit things for a while...
I've just been talking about 2.6, so "long time ago" can't be that long :-) I have the updates to the exception handler so the PTEs get loaded correctly, that's on the way. I think 2.4 should be OK if anyone is using that.
The one that bothers me is this patch I've been sitting on for quite some time. It's not specific to Alchemy, it's a generic MIPS page table issue. The problem started when someone loaded very large modules which caused a new kernel page table to be allocated. For some reason I don't remember, the vmalloc_fault fixup didn't handle this, and the applications would crash the system because their pgd page didn't get updated to reflect this. The address must have been in the vmalloc space, but I no longer have the system for testing (but the code is running in a several thousand real products). The only way I could make this work is to test the fault address, the most significant bit anyway, in the TLB miss handler to see if it was a user or kernel address. If it was a kernel address, I loaded the init_mm pgd instead of the thread pgd. Just one test and a couple of instructions, but it was necessary. I'm still puzzling, but will remember :-)
Thanks.
-- Dan
