Re: [Qemu-devel] [PATCH V8 4/4] tests: Add migration test for aarch64

[Andrew Jones]

On Tue, Sep 04, 2018 at 01:07:56PM -0400, Wei Huang wrote:
> 
> 
> ----- Original Message -----
> > From: "Andrew Jones" <address@hidden>
> > To: "Wei Huang" <address@hidden>
> > Cc: address@hidden, address@hidden, "peter maydell" <address@hidden>, 
> > address@hidden,
> > address@hidden
> > Sent: Monday, September 3, 2018 6:53:35 AM
> > Subject: Re: [Qemu-devel] [PATCH V8 4/4] tests: Add migration test for 
> > aarch64
> > 
> > On Sat, Sep 01, 2018 at 01:11:15AM -0400, Wei Huang wrote:
> > > +.section .text
> > > +
> > > +        .globl  _start
> > > +
> > > +_start:
> > > +        /* disable MMU to use phys mem address */
> > > +        mrs     x0, sctlr_el1
> > > +        bic     x0, x0, #(1<<0)
> > > +        msr     sctlr_el1, x0
> > > +        isb
> > > +
> > > +        /* traverse test memory region */
> > > +        mov     x0, #ARM_TEST_MEM_START
> > > +        mov     x1, #ARM_TEST_MEM_END
> > 
> > I don't think there's any reason to require the start and
> > end addresses to be hard coded. We should be able to get
> > the start address with
> 
> Are you saying that we should make the .S file as independent as possible? 
> These variables need to be defined for migration-test.c anyway. Why can't we 
> just use them here?

If we ever change the base address of mach-virt, or want to reuse this
code for another AArch64 machine model that has a different base address,
then it would just work, when we don't hard code discoverable variables.
But, you're right, migration-test.c, would need to change in some way
to be reusable, or to handle different base addresses anyway, so I
guess I'm OK with just hard coding them here too.

Thanks,
drew

> 
> > 
> > #define KERNEL_OFFSET 0x80000
> >            adr     x0, _start
> >            add     x0, x0, #(1024 * 1024 - KERNEL_OFFSET)
> > 
> > and the end address with
> > 
> >            add     x1, x0, #(99 * 1024 * 1024)
> > 
> > Thanks,
> > drew
> >