Re: [PATCH v1 04/12] xen/hvmlite: Bootstrap HVMlite guest

[Boris Ostrovsky]

On 01/22/2016 06:32 PM, Luis R. Rodriguez wrote:
> On Fri, Jan 22, 2016 at 04:35:50PM -0500, Boris Ostrovsky wrote:
>
> > +/*
> > + * This routine (and those that it might call) should not use
> > + * anything that lives in .bss since that segment will be cleared later
> > + */
> > +void __init xen_prepare_hvmlite(void)
> > +{
> > +	u32 eax, ecx, edx, msr;
> > +	u64 pfn;
> > +
> > +	cpuid(xen_cpuid_base() + 2, &eax, &msr, &ecx, &edx);
> > +	pfn = __pa(hypercall_page);
> > +	wrmsr_safe(msr, (u32)pfn, (u32)(pfn >> 32));
> > +
> > +	pv_info.name = "Xen HVMlite";
> > +	xen_domain_type = XEN_HVM_DOMAIN;
> > +	xen_hvmlite = 1;
> > +
> > +	x86_init.oem.arch_setup = xen_init_kernel;
> > +	x86_init.oem.banner = xen_banner;
> > +
> > +	hvmlite_bootparams();
> > +}
> > +#endif
> If the boot_params.hdr.hardware_subarch_data pointed to a custom
> struct then the first C entry point for Xen could shuffle this and
> set this too, by still using less asm entry helpers. We'd still
> need this run but with the linker table I think we could have
> a stub small stub for hvm run, it would not be a call from asm.

Perhaps, but someone would still have to set hardware_subarch. And it's 
hvmlite_bootparams() that does it.

And that's not sufficient, I think. There are still some things that 
trampoline code sets up (e.g. page tables for 64-bit).

-boris