Re: [Qemu-devel] AArch64 register SP value always appearing as zero in "info registers" (kvm control)

[Peter Maydell]

On 20 February 2014 13:40, Claudio Fontana <address@hidden> wrote:
> Hello,
>
> I am running kvm controlled qemu using mach virt,
>
> and I have this glitch where the SP value in "info registers" always
> appears as zero to me:
>
> (qemu) info registers
> PC=00000000400b0044  SP=0000000000000000
> X00=0000000040324000 X01=0000000040331000 X02=00000000400b0000
> X03=0000000000000000
> X04=0000000040080000 X05=0000000000000000 X06=0000000000000000
> X07=0000000000000000
> X08=0000000000000000 X09=0000000000000000 X10=0000000000000000
> X11=0000000000000000
> X12=0000000000000000 X13=0000000000000000 X14=0000000000000000
> X15=0000000000000000
> X16=0000000000000000 X17=0000000000000000 X18=0000000000000000
> X19=0000000000000000
> X20=0000000000000000 X21=0000000000000000 X22=0000000000000000
> X23=0000000000000000
> X24=0000000000000000 X25=0000000000000000 X26=0000000000000000
> X27=0000000000000000
> X28=0000000000000000 X29=0000000040324000 X30=00000000400b0014
> PSTATE=600003c5 (flags -ZC-)
>
> In the guest I am doing
>
> adrp x0, something
> mov sp, x0
> mov x29, sp
>
> and while I can see the x29 value (seen above), my SP still appears as zero..
>
> I am at commit 91abb80b5f66e8387ae1a5ba85083e49b877938c (7th February)
>
> Any idea about what could be wrong?

The code doesn't look obviously wrong; I suggest you stick
some debug printfs/breakpoints/etc in:
 target-arm/kvm64.c:kvm_arch_get_registers() where we ask
   the kernel for the value of SP and put it in xregs[31]
 target-arm/gdbstub64.c:aarch64_cpu_gdb_read_register()
   where we return xregs[31] when gdb asks for it

also enabling gdb's "debug all protocol packets" feature
may help.

thanks
-- PMM