On Fri, Jun 10, 2011 at 11:58 AM, Catalin Marinas
<catalin.mari...@arm.com> wrote:
> On Fri, Jun 10, 2011 at 10:53:06AM +0100, Alexander Graf wrote:
>> Am 10.06.2011 um 11:23 schrieb Catalin Marinas <catalin.mari...@arm.com>:
>> > On Fri, Jun 10, 2011 at 09:40:34AM +0100, Christoffer Dall wrote:
>> >> OK, so I looked into compiling KVM/ARM as a module and there are a few
>> >> obstacles:
>> >>
>> >> I need to export several symbols (identitiy_mapping_add,
>> >> pgd_clear_bad, __irq_svc). __irq_svc is tricky because it's in the
>> >> entry-armv.S assembly file, so it's not obvious where to export it
>> >> from. Recommendations? (dedicated KVM export file as in PPC or simply
>> >> adding EXPORT_SYMBOL_GPL(...) or alternative?
>> >
>> > There is arch/arm/kernel/armksyms.c where we export extra symbols coming
>> > from .S files. I haven't looked at the code yet, maybe some of the
>> > symbols could be avoided.
>> >
>> >> Also, iirc, modules are loaded using vmalloc, wouldn't that make it
>> >> impossible for me to use virt_to_phys, which I need to do on some of
>> >> the code pages for Hypervisor initialization? If any of the ARM people
>> >> could give an advise here, it would be much appreciated - of course I
>> >> can kmalloc a page and relocate the init code, but I really would like
>> >> to avoid this.
>> >
>> > You could alloc a page (or a few) an copy the hypervisor code in there.
>> > Just make sure that it is position independent (which is not difficult
>> > with hand-written assembly).
>>
>> What we do on ppc is to select another kernel option =Y when we set
>> kvm=M. Based on that other option, we then add the code that need to
>> run in real mode (linear map) to the main kernel binary.
>>
>> That way, the guest entry/exit code for example is always in the
>> kernel, while the logic that dispatches what to do on a specific guest
>> exit can stay as module, making development a lot easier.
>
> Good point. We could do the same on ARM.

Thanks, I will follow your suggestions for next patch series.
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