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:

quoted

From: Tom Lendacky <thomas.lendacky@amd.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@amd.com>
Signed-off-by: Brijesh Singh <redacted>
---
  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

quoted

+	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.

quoted

+
  	/* 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

quoted

+
  		efi_update_mappings(md, pf);

In general, I'm not totally excited about that sprinkling of if
(sev_active())... :-\