Re: [PATCH v9 32/43] x86/boot: Add a pointer to Confidential Computing blob in bootparams

Borislav Petkov
2022-02-05T13:07:51Z

On Fri, Jan 28, 2022 at 11:17:53AM -0600, Brijesh Singh wrote:
> From: Michael Roth <michael.roth@amd.com>
>
> The previously defined Confidential Computing blob is provided to the
> kernel via a setup_data structure or EFI config table entry. Currently
> these are both checked for by boot/compressed kernel to access the
> CPUID table address within it for use with SEV-SNP CPUID enforcement.
>
> To also enable SEV-SNP CPUID enforcement for the run-time kernel,
> similar early access to the CPUID table is needed early on while it's
> still using the identity-mapped page table set up by boot/compressed,
> where global pointers need to be accessed via fixup_pointer().
>
> This isn't much of an issue for accessing setup_data, and the EFI
> config table helper code currently used in boot/compressed *could* be
> used in this case as well since they both rely on identity-mapping.
> However, it has some reliance on EFI helpers/string constants that
> would need to be accessed via fixup_pointer(), and fixing it up while
> making it shareable between boot/compressed and run-time kernel is
> fragile and introduces a good bit of uglyness.
>
> Instead, add a boot_params->cc_blob_address pointer that the
> boot/compressed kernel can initialize so that the run-time kernel can
> access the CC blob from there instead of re-scanning the EFI config
> table.
>
> Signed-off-by: Michael Roth <michael.roth@amd.com>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
> arch/x86/include/asm/bootparam_utils.h | 1 +
> arch/x86/include/uapi/asm/bootparam.h | 3 ++-
> 2 files changed, 3 insertions(+), 1 deletion(-)

Another review comment ignored:

https://lore.kernel.org/r/YeWyCtr11rL7dxpT@zn.tnic

/me ignores this patch too.

--
Regards/Gruss,
Boris.