Hi Aashish,
Following is an example of the linux code where it uses lwarx and stcwx.
1: lwarx %0,0,%3 # atomic_add\n\
add %0,%2,%0\n"
PPC405_ERR77(0,%3)
" stwcx. %0,0,%3 \n\
bne- 1b"
As you would notice after stcwx it checks for equal bit in the cr register. So I think in your code
you should also update the cr register after stcwx for the guest.
Regards
Varun
> -----Original Message-----
> From: kvm-ppc-owner@xxxxxxxxxxxxxxx [mailto:kvm-ppc-
> owner@xxxxxxxxxxxxxxx] On Behalf Of Aashish Mittal
> Sent: Tuesday, March 06, 2012 2:07 AM
> To: kvm-ppc@xxxxxxxxxxxxxxx
> Subject: Emulating lwarx and stwcx instructions in PowerPc BOOKE e500
>
> Hi
> I'm working on powerpc booke architecture and my project requires me to
> remove read and write privileges on some pages. Due to this any
> instruction accessing these pages traps and i'm trying to emulate the
> behavior of these instructions.
>
> I've emulated lwarx and stwcx instruction but i think stwcx is not
> working correctly. The emulation i've written is written below
>
> case OP_31_XOP_LWARX:
> {
> ulong ret;
> ulong addr;
> int eh = inst & 0x00000001 ;
> kvm_gva_to_hva(vcpu,ea,&addr);
> /*lwarx RT RA RB EH*/
> if(eh == 0)
> __asm__ __volatile__("lwarx %0,0,%1,0; isync":"=r" (ret) :"r"
> (addr));
> else
> __asm__ __volatile__("lwarx %0,0,%1,1; isync":"=r" (ret) :"r"
> (addr));
>
> kvmppc_set_gpr(vcpu,rt,ret);
> }
>
> case OP_31_XOP_STWCX:
> {
> ulong tmp;
> ulong addr;
> ulong data;
> kvm_gva_to_hva(vcpu,ea,&addr);
> kvmppc_read_guest(vcpu,ea,&data,sizeof(data));
> __asm__ __volatile__("stwcx. %1,0,%2; isync"
> :"=r" (tmp):"r" (data),"r" (addr):"memory");
>
> }
>
> Here kvm_gva_to_hva function convrets a guest effective address to host
> virtual address .
>
> void kvm_gva_to_hva(struct kvm_vcpu *vcpu, ulong ea,ulong* hva) {
> gfn_t gfn;
> gpa_t gpa ;
> int gtlb_index;
> int offset;
> ulong addr;
> struct kvmppc_vcpu_e500 *vcpu_e500 = to_e500(vcpu);
>
> gtlb_index = kvmppc_mmu_itlb_index(vcpu, ea);
> gpa = kvmppc_mmu_xlate(vcpu,gtlb_index, ea);
> gfn = gpa >> PAGE_SHIFT;
> addr = (ulong)gfn_to_hva(vcpu_e500->vcpu.kvm, gfn);
> offset = offset_in_page(gpa);
>
> *hva = addr + offset;
> return;
> }
>
> The guest just hangs once it encounters a stwcx instruction. Does anybody
> have any idea why this is not working and what's wrong about the
> emulation code.
>
> Also i'm working on linux-3.0-rc4 kernel .
>
> Thanks in advance
>
>
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