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

Borislav Petkov
2017-07-27T13:31:25Z

On Mon, Jul 24, 2017 at 02:07:46PM -0500, Brijesh Singh wrote:
> From: Tom Lendacky <thomas.lendacky@amd.com>
>
> 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@amd.com>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
> 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 Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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