Re: [Xen-devel] [PATCH v1 9/9] livepatch: tests: Make them compile under ARM64

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

> > > > +#else
> > > > +     asm(ALTERNATIVE("nop", "nop", 1));
> > > 
> > > Why the hardcoded 1 here? I am wondering if we should introduce a new
> > > capability "LIVEPATCH_TEST" which is enabled by default. So we can test 
> > > that
> > > the the alternative is working on all the platform. What do you think?
> > 
> > Sure, but I am not sure what number you would like? Perhaps 42 :-) ?
> 
> Unfortunately the number is an index in the bitmap, so we have to allocate
> them contiguously.

OK.
> 
> Also, this made me realize that the current implementation of
> apply_alternatives cannot work if we are patching outside the xen binary. :/

Oh yeah. The vmap part :-)
> 
> I need to have a think to see how we can handle any region.

We can just double-check that the region->begin address >= __alt_instructions
and region->End <= __alt_instructions_end and then use vmap.

Otherwise, just writemap = replptr I think?

Let me prep a patch and test it.
> 
> Cheers,
> 
> -- 
> Julien Grall

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