Re: [RFC Part1 PATCH v3 06/17] x86/mm: Use encrypted access of boot related data with SEV

[Borislav Petkov]

On Mon, Jul 24, 2017 at 02:07:46PM -0500, Brijesh Singh wrote:
> From: Tom Lendacky <thomas.lendacky@xxxxxxx>
> 
> When Secure Encrypted Virtualization (SEV) is active, boot data (such as
> EFI related data, setup data) is encrypted and needs to be accessed as
> such when mapped. Update the architecture override in early_memremap to
> keep the encryption attribute when mapping this data.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
> ---
>  arch/x86/mm/ioremap.c | 44 ++++++++++++++++++++++++++++++++------------
>  1 file changed, 32 insertions(+), 12 deletions(-)

...

> @@ -590,10 +598,15 @@ bool arch_memremap_can_ram_remap(resource_size_t phys_addr, unsigned long size,
>  	if (flags & MEMREMAP_DEC)
>  		return false;
>  
> -	if (memremap_is_setup_data(phys_addr, size) ||
> -	    memremap_is_efi_data(phys_addr, size) ||
> -	    memremap_should_map_decrypted(phys_addr, size))
> -		return false;
> +	if (sme_active()) {
> +		if (memremap_is_setup_data(phys_addr, size) ||
> +		    memremap_is_efi_data(phys_addr, size) ||
> +		    memremap_should_map_decrypted(phys_addr, size))
> +			return false;
> +	} else if (sev_active()) {
> +		if (memremap_should_map_decrypted(phys_addr, size))
> +			return false;
> +	}
>  
>  	return true;
>  }

I guess this function's hind part can be simplified to:

        if (sme_active()) {
                if (memremap_is_setup_data(phys_addr, size) ||
                    memremap_is_efi_data(phys_addr, size))
                        return false;
        }

        return ! memremap_should_map_decrypted(phys_addr, size);
}

> @@ -608,15 +621,22 @@ pgprot_t __init early_memremap_pgprot_adjust(resource_size_t phys_addr,
>  					     unsigned long size,
>  					     pgprot_t prot)

And this one in a similar manner...

>  {
> -	if (!sme_active())
> +	if (!sme_active() && !sev_active())
>  		return prot;

... and you don't need that check...

> -	if (early_memremap_is_setup_data(phys_addr, size) ||
> -	    memremap_is_efi_data(phys_addr, size) ||
> -	    memremap_should_map_decrypted(phys_addr, size))
> -		prot = pgprot_decrypted(prot);
> -	else
> -		prot = pgprot_encrypted(prot);
> +	if (sme_active()) {

... if you're going to do it here too.

> +		if (early_memremap_is_setup_data(phys_addr, size) ||
> +		    memremap_is_efi_data(phys_addr, size) ||
> +		    memremap_should_map_decrypted(phys_addr, size))
> +			prot = pgprot_decrypted(prot);
> +		else
> +			prot = pgprot_encrypted(prot);
> +	} else if (sev_active()) {

And here.

> +		if (memremap_should_map_decrypted(phys_addr, size))
> +			prot = pgprot_decrypted(prot);
> +		else
> +			prot = pgprot_encrypted(prot);
> +	}

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix ImendÃrffer, Jane Smithard, Graham Norton, HRB 21284 (AG NÃrnberg)
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