Hi, I would like to understand certain aspects of dynamic translation which Qemu employs to run the guest OS. I have read the qemu paper and this query is beyond that.
My understanding is as follows: 1. Qemu slices the guest os binary into blocks and then asks the Host OS to execute it and return the result 2. In the above, without the accelerator module, Qemu does dynamic translation of guest_asm -> c_func -> host_asm. With the accelerator this conversion doesn't happen as the guest_asm and host_asm are the same. 3. Now before a block is executed the cpu_clock_ticks is updated in main_loop_wait and after the block is executed the cpu_clock_ticks is again updated based on the number of ticks that have gone by in the host_os during the execution. Is my understanding correct ? I think the qemu system works like this because qemu is still a process under the host os and hence cannot guarantee to the guest os how long it will take for qemu to execute guest_os instructions. One simple scenario could be the user in the host os suspends the qemu process for a while... 4. The interesting part happens when qemu encourters an already translated block. I understand that for efficiency qemu caches block based on some kind of signature and when the same block appears qemu simply uses the translated binary instead of re-translating it I have two questions here. a. How does qemu slice the guest binary into blocks ? any rational or rule of thumb here ? b. Once a block is generated some ID should be assigned to it right ? in which src file it is stored ? c. The next time a src block with the same signature is encountered the cached host binary is used right ? -- How does qemu detect that is the same guest block ? md5sum or other fingerprinting methods ? d. Does this caching happen even with accelerator module running ? I understand my questions are deep into the design of qemu itself. Can I request Fabrice or the core team to help me out here ? regards, Krishnan _______________________________________________ Qemu-devel mailing list Qemu-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/qemu-devel
