From mboxrd@z Thu Jan  1 00:00:00 1970
From: Aashish Mittal <aashish.mittal4u@gmail.com>
Date: Thu, 25 Aug 2011 09:31:53 +0000
Subject: Re: Emulating LWZU Instruction for e500 powerpc
Message-Id: <loom.20110825T112251-213@post.gmane.org>
List-Id: <kvm-ppc.vger.kernel.org>
References: <loom.20110819T134401-946@post.gmane.org>
In-Reply-To: <loom.20110819T134401-946@post.gmane.org>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
To: kvm-ppc@vger.kernel.org

Alexander Graf <agraf <at> suse.de> writes:

> 
> 
> 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, wantu703268, limit&2144
> > 
> > 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 . 

Thanks for you help
Aashish Mittal