Re: [Xen-devel] [PATCH v7 19/36] x86/mm: Add support to access boot related data in the clear

[Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>]

On Fri, 16 Jun, at 01:53:26PM, Tom Lendacky wrote:
> Boot data (such as EFI related data) is not encrypted when the system is
> booted because UEFI/BIOS does not run with SME active. In order to access
> this data properly it needs to be mapped decrypted.
> 
> Update early_memremap() to provide an arch specific routine to modify the
> pagetable protection attributes before they are applied to the new
> mapping. This is used to remove the encryption mask for boot related data.
> 
> Update memremap() to provide an arch specific routine to determine if RAM
> remapping is allowed.  RAM remapping will cause an encrypted mapping to be
> generated. By preventing RAM remapping, ioremap_cache() will be used
> instead, which will provide a decrypted mapping of the boot related data.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> ---
>  arch/x86/include/asm/io.h |    5 +
>  arch/x86/mm/ioremap.c     |  179 
> +++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/io.h        |    2 +
>  kernel/memremap.c         |   20 ++++-
>  mm/early_ioremap.c        |   18 ++++-
>  5 files changed, 217 insertions(+), 7 deletions(-)

Reviewed-by: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>

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