Re: [PATCH v5 17/32] x86/mm: Add support to access boot related data in the clear

[Tom Lendacky]

On 5/18/2017 4:02 AM, Borislav Petkov wrote:
> On Wed, May 17, 2017 at 01:54:39PM -0500, Tom Lendacky wrote:
> > I was worried what the compiler might do when CONFIG_EFI is not set,
> > but it appears to take care of it. I'll double check though.
>
> There's a efi_enabled() !CONFIG_EFI version too, so should be fine.
>
> > I may introduce a length variable to capture data->len right after
> > paddr_next is set and then have just a single memunmap() call before
> > the if check.
>
> Yap.
>
> > I tried that, but calling an "__init" function (early_memremap()) from
> > a non "__init" function generated warnings. I suppose I can pass in a
> > function for the map and unmap but that looks worse to me (also the
> > unmap functions take different arguments).
>
> No, the other way around: the __init function should call the non-init
> one and you need the non-init one anyway for memremap_is_setup_data().

The "worker" function would be doing the loop through the setup data,
but since the setup data is mapped inside the loop I can't do the __init
calling the non-init function and still hope to consolidate the code.
Maybe I'm missing something here...

Thanks,
Tom

> > This is like the chicken and the egg scenario. In order to determine if
> > an address is setup data I have to explicitly map the setup data chain
> > as decrypted. In order to do that I have to supply a flag to explicitly
> > map the data decrypted otherwise I wind up back in the
> > memremap_is_setup_data() function again and again and again...
>
> Oh, fun.