On 03/06/2012 02:30 PM, Aashish Mittal wrote: > I'm thinking of emulating the lwarx and stwcx instruction as follows > > 1) to emulate lwarx i will just do a load word instruction . > In order to emulate lwarx correctly, i will need to setup a global > reservation structure, which has a reservation entry for each CPU. > Upon making the lwarx, i will set the internal reserve bit, then setup a > snoop address. All writes to the memory block that the address is in > will destroy the reservation in this structure. > Since i'm not calling a direct lwarx instruction upon encountering a lwarx in > guest this will not leave a reservation when i'm returning to guest. > > 2) Upon encountering a stwcx instruction in guest i can match the > reservation address > as stored in my global reservation structure. If it matches then i can > fire a dummy lwarx > first in host and then fire the stwcx. Why bother with the dummy lwarx and stwcx? Just do an ordinary store. You'll want to use a mutex in KVM to protect from multiple vcpus accessing the region at once. Also check whether you're on a CPU that's supposed to clear reservations on interrupts. > Will that work ? It should, as long as you aren't sharing this memory with anything that can access it directly (no emulation) that will be writing to the reservation granule or using lwarx/stwcx itself. But why do you need this? -Scott -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
