Re: [RFC PATCH v2 2/3] efi: Reserve confidential computing secret area

Hi Tom,

On 28/06/2021 23:40, Tom Lendacky wrote:

On 6/28/21 1:34 PM, Dov Murik wrote:

quoted

When efi-stub copies an EFI-provided confidential computing secret area,
reserve that memory block for future use within the kernel.

Signed-off-by: Dov Murik <redacted>
---
 drivers/firmware/efi/Makefile                 |  2 +-
 drivers/firmware/efi/confidential-computing.c | 41 +++++++++++++++++++
 drivers/firmware/efi/efi.c                    |  5 +++
 include/linux/efi.h                           |  4 ++
 4 files changed, 51 insertions(+), 1 deletion(-)
 create mode 100644 drivers/firmware/efi/confidential-computing.c

diff --git a/include/linux/efi.h b/include/linux/efi.h
index 4f647f1ee298..e9740bd16db0 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h

@@ -551,6 +551,8 @@ extern struct efi {
 	unsigned long			tpm_log;		/* TPM2 Event Log table */
 	unsigned long			tpm_final_log;		/* TPM2 Final Events Log table */
 	unsigned long			mokvar_table;		/* MOK variable config table */
+	unsigned long			confidential_computing_secret;	/* Confidential computing */
+									/* secret table           */

If there is any possibility that someone could reuse a form of this
confidential computing secret table in a bare metal system, then this
table needs to be added to the efi_tables[] array in
arch/x86/platform/efi/efi.c. Otherwise, it will be mapped improperly on a
system with SME active.

Good catch, thanks.  I see that all existing table addresses from
struct efi are added to the efi_tables[] array, so for completeness it
makes sense to add efi.confidential_computing_secret as well (even
though currently bare metal firmware doesn't have this table).

Thanks,
-Dov

Thanks,
Tom

quoted

 
 	efi_get_time_t			*get_time;
 	efi_set_time_t			*set_time;

@@ -1190,6 +1192,8 @@ extern int efi_tpm_final_log_size;
 
 extern unsigned long rci2_table_phys;
 
+extern int efi_confidential_computing_secret_area_reserve(void);
+
 /*
  * efi_runtime_service() function identifiers.
  * "NONE" is used by efi_recover_from_page_fault() to check if the page