Hi, On Mon, Oct 12, 2009 at 10:51 PM, Swapnil Pimpale <swapnil.p...@gmail.com> wrote: > Actually we are doing an academic project in which we need to have two cores > of Intel Core 2 Duo, running inside the GRUB simultaneously. For that we > need to send an IPI from primary core to the secondary core. Can you > suggest any pointers to implement this? Has someone done anything similar to > this before?
Is there any sane reason for this? None of GRUB's code is designed for multiple CPUs, and I'd assume that no firmware is designed to handle multiple CPUs either (I know that "PC BIOS" isn't), and I expect that if you wasted your time and got multiple CPUs running inside GRUB then one of the CPUs would do everything while any extra CPU/s would do nothing (until an OS is started and you need to shut down the "do nothing" CPU/s). The method for starting extra CPUs (for 80x86 only) is: - find the ACPI "APIC" table and get the address of the local APIC and the APIC ID for the CPU/s you want to start - if there's no ACPI, use the "Multi-Processor Specification" tables to find the address of the local APIC and the APIC ID for the CPU/s you want to start (you shouldn't need to do this on modern systems) - get the local APIC version (from either ACPI, MP spec or directly from the BSP's local APIC) and determine what type of APIC it is - (for "xAPIC" only) send an INIT IPI - (for "xAPIC" only) wait 10 ms - (for "xAPIC" only) send a SIPI IPI - (for "xAPIC" only) wait for up to 200 us for the other CPU to set a "I started" flag - (for "xAPIC" only) if the "I started" flag wasn't set in time, send another SIPI IPI - (for "xAPIC" only) if the "I started" flag wasn't set in time, wait for a while (at least 200 s, but typically several seconds for the other CPU to set a "I started" flag The SIPI IPI includes the address that you want the other CPU to start executing. This needs to be on a page boundary and must be below 0x00100000. The other CPU will start in real mode, and one of the first things it should do is set some sort of "I started" flag (to tell the first CPU that it can stop waiting and that there hasn't been some sort of "CPU failed to start" error). For different types of local APIC there's variations, but you probably don't need to care about the old 82489DX local APICs (only used on 80486 and early Pentium); and the new "x2APIC" is compatible with the "xAPIC" (unless there's a very large number of CPUs present and the APIC ID for the CPU/s you want to start is above 0x000000FF). For reference materials, see Intel's System Programming Guide, Intel's Multi-Processor Specification (even if you're using ACPI), the ACPI specification, and generic OS development resources (e.g. http://www.osdev.org/, the #osdev IRC channel, etc). Cheers, Brendan _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org http://lists.gnu.org/mailman/listinfo/grub-devel
