On 25.08.2011, at 04:30, Aashish Mittal wrote: > > On Thu, Aug 25, 2011 at 4:04 AM, Alexander Graf <agraf@xxxxxxx> wrote: > > On 19.08.2011, at 06:45, Aashish Mittal wrote: > > > Hi > > I'm trying to emulate the lwzu instruction in e500 powerpc kvm for my project . > > I've removed the read and write privileges from the tlb entries of guest's > > certain pages . So when i'm trying to emulate lwzu instruction i'm getting a > > kernel panic while mounting the guest filesystem while booting . > > > > attempt to access beyond end of device > > ram0: rw=0, want=75703268, limit=262144 > > > > To make sure that the emulation is faulty what i'm trying to do now is at the > > time of DATA STORAGE exit on a marked page by an lwzu instruction i'm patching > > the next instruction with an instruction which will raise an INTERRUPT PROGRAM > > EXCEPTION and will get trapped in kvm and then i'm reverting the old read and > > write privileges of this page and resuming the guest so that this LWZU > > instruction can run natively . I'm expecting the immediate next instruction to > > raise the INTERRUPT PROGRAM EXCEPTION but all i'm getting are DATA STORAGE Exits > > at other pages marked by me and DTLB and ITLB misses on other addresses . > > > > I've made sure to flush the icache after i patch using the instruction > > flush_icache_range . > > > > Error Log : > > Emulating a lwzu instruction on pc 0xc00161ac && eaddr 0xc05742f0 > > Original Instruction is 0x90e60004 at pc: 0xc00161b0 > > Modified Instruction is 0x7ce000a6 at pc: 0xc00161b0 > > Exit : Interrupt DATA STORAGE at pc 0xc000f210 on eaddr:0xc000f228 instruction: > > 0x8085001c > > > > Why i'm not getting any INTERRUPT PROGRAM EXCEPTION immediately in the next > > instruction ? > > Hrm. Are you sure you're actually modifying the instruction? This looks like you're running Linux, so you could try and just put a "b ." instruction right after the instruction you're trying to patch up and examine memory from Qemu :) > > > Alex > > I checked the memory by reading the guest page at the modified instruction and it is the modified instruction . I think the reason i'm not getting the EXIT is because the icache is not getting flushed properly. > I'm trying to to flush the icache entries of the guest while i'm inside the host kvm . I'm trying to use flush_icache_range(pc , pc+ 4 ) where this pc is the guest pc eaddr where i'm modifying the instruction . > > Do you have any idea how to flush the guest entries while i'm inside the host os given the guest eaddr of the address where i'm trying to patch the instruction . You need to do the icache flush on the effective address you were writing to, not the guest effective address :) Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
