On 12/28/2011 01:12 AM, Xin Tong wrote: > QEMU does not exit and handle interrupt within translation blocks. it > only exits after the translation block is finished. Assuming a > translation block is very long, is it possible that QEMU could have > exceeded the interrupt's "timing window" and yields unexpected > behavior. > > The reason I ask is that I am searching for alternatives to QEMU > current way of handling interrupt (unlink translation blocks on > interrupt). However, an obvious approach - checking for interrupt in > every basic block, seems to be too heavy ( too many tb enters/exits > ). Maybe checking interrupt in a few basic blocks might be better, but > what is a good measure for the number of basic blocks to execute > before checking for interrupt ? >
It's possible to check for an interrupt before every instruction, without any overhead: - when a signal arrives, check the instruction pointer. If it points outside tcg code, set a flag and return. - consult a table indexed by the instruction pointer, that gives the number of bytes to the next guest instruction boundary - if nonzero, set a breakpoint at that boundary, and resume - remove the breakpoint (if set) - adjust the TB to return on the current instruction pointer - return -- error compiling committee.c: too many arguments to function
