linux-kernel - Re: [RFC Part1 PATCH v3 08/17] x86/efi: Access EFI data as encrypted when SEV is active

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Date:   Thu, 17 Aug 2017 13:42:04 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Borislav Petkov <bp@...e.de>, Brijesh Singh <brijesh.singh@....com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-efi@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        kvm@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        Piotr Luc <piotr.luc@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Reza Arbab <arbab@...ux.vnet.ibm.com>,
        David Howells <dhowells@...hat.com>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Laura Abbott <labbott@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Eric Biederman <ebiederm@...ssion.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Jonathan Corbet <corbet@....net>,
        Dave Airlie <airlied@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Arnd Bergmann <arnd@...db.de>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>
Subject: Re: [RFC Part1 PATCH v3 08/17] x86/efi: Access EFI data as encrypted
 when SEV is active

On 7/28/2017 5:31 AM, Borislav Petkov wrote:
> On Mon, Jul 24, 2017 at 02:07:48PM -0500, Brijesh Singh wrote:
>> From: Tom Lendacky <thomas.lendacky@....com>
>>
>> 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@....com>
>> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
>> ---
>>   arch/x86/platform/efi/efi_64.c | 15 ++++++++++++++-
>>   1 file changed, 14 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
>> index 12e8388..1ecb3f6 100644
>> --- a/arch/x86/platform/efi/efi_64.c
>> +++ b/arch/x86/platform/efi/efi_64.c
>> @@ -32,6 +32,7 @@
>>   #include <linux/reboot.h>
>>   #include <linux/slab.h>
>>   #include <linux/ucs2_string.h>
>> +#include <linux/mem_encrypt.h>
>>   
>>   #include <asm/setup.h>
>>   #include <asm/page.h>
>> @@ -369,7 +370,10 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
>>   	 * as trim_bios_range() will reserve the first page and isolate it away
>>   	 * from memory allocators anyway.
>>   	 */
>> -	if (kernel_map_pages_in_pgd(pgd, 0x0, 0x0, 1, _PAGE_RW)) {
>> +	pf = _PAGE_RW;
>> +	if (sev_active())
>> +		pf |= _PAGE_ENC;
> 
> \n here
> 
>> +	if (kernel_map_pages_in_pgd(pgd, 0x0, 0x0, 1, pf)) {
>>   		pr_err("Failed to create 1:1 mapping for the first page!\n");
>>   		return 1;
>>   	}
>> @@ -412,6 +416,9 @@ static void __init __map_region(efi_memory_desc_t *md, u64 va)
>>   	if (!(md->attribute & EFI_MEMORY_WB))
>>   		flags |= _PAGE_PCD;
>>   
>> +	if (sev_active())
>> +		flags |= _PAGE_ENC;
>> +
>>   	pfn = md->phys_addr >> PAGE_SHIFT;
>>   	if (kernel_map_pages_in_pgd(pgd, pfn, va, md->num_pages, flags))
>>   		pr_warn("Error mapping PA 0x%llx -> VA 0x%llx!\n",
>> @@ -511,6 +518,9 @@ static int __init efi_update_mappings(efi_memory_desc_t *md, unsigned long pf)
>>   	pgd_t *pgd = efi_pgd;
>>   	int err1, err2;
>>   
>> +	if (sev_active())
>> +		pf |= _PAGE_ENC;
> 
> Move this assignment to the caller efi_update_mem_attr() where pf is being
> set...

Will do.

> 
>> +
>>   	/* Update the 1:1 mapping */
>>   	pfn = md->phys_addr >> PAGE_SHIFT;
>>   	err1 = kernel_map_pages_in_pgd(pgd, pfn, md->phys_addr, md->num_pages, pf);
>> @@ -589,6 +599,9 @@ void __init efi_runtime_update_mappings(void)
>>   			(md->type != EFI_RUNTIME_SERVICES_CODE))
>>   			pf |= _PAGE_RW;
>>   
>> +		if (sev_active())
>> +			pf |= _PAGE_ENC;
> 
> ... just like here.

Yup.

Thanks,
Tom

> 
>> +
>>   		efi_update_mappings(md, pf);
> 
> In general, I'm not totally excited about that sprinkling of if
> (sev_active())... :-\
>