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

From: Borislav Petkov
Date: Thu May 18 2017 - 05:02:37 EST

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.


> 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().

> 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.


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