On 09/22/2016 09:35 AM, Borislav Petkov wrote:
> On Mon, Aug 22, 2016 at 07:25:25PM -0400, Brijesh Singh wrote:
>> From: Tom Lendacky <thomas.lendacky@xxxxxxx>
>>
>> EFI data is encrypted when the kernel is run under SEV. Update the
>> page table references to be sure the EFI memory areas are accessed
>> encrypted.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
>> ---
>> arch/x86/platform/efi/efi_64.c | 14 ++++++++++++--
>> 1 file changed, 12 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
>> index 0871ea4..98363f3 100644
>> --- a/arch/x86/platform/efi/efi_64.c
>> +++ b/arch/x86/platform/efi/efi_64.c
>> @@ -213,7 +213,7 @@ void efi_sync_low_kernel_mappings(void)
>>
>> int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
>> {
>> - unsigned long pfn, text;
>> + unsigned long pfn, text, flags;
>> efi_memory_desc_t *md;
>> struct page *page;
>> unsigned npages;
>> @@ -230,6 +230,10 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
>> efi_scratch.efi_pgt = (pgd_t *)__sme_pa(efi_pgd);
>> pgd = efi_pgd;
>>
>> + flags = _PAGE_NX | _PAGE_RW;
>> + if (sev_active)
>> + flags |= _PAGE_ENC;
>
> So this is confusing me. There's this patch which says EFI data is
> accessed in the clear:
>
> https://lkml.kernel.org/r/20160822223738.29880.6909.stgit@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> but now here it is encrypted when SEV is enabled.
>
> Do you mean, it is encrypted here because we're in the guest kernel?
Yes, the idea is that the SEV guest will be running encrypted from the
start, including the BIOS/UEFI, and so all of the EFI related data will
be encrypted.
Thanks,
Tom
>
> Thanks.
>
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