From 1227418989346af3af179742cf42ce842e0ad484 Mon Sep 17 00:00:00 2001 From: Dov Murik Date: Tue, 12 Apr 2022 21:21:24 +0000 Subject: efi: Save location of EFI confidential computing area Confidential computing (coco) hardware such as AMD SEV (Secure Encrypted Virtualization) allows a guest owner to inject secrets into the VMs memory without the host/hypervisor being able to read them. Firmware support for secret injection is available in OVMF, which reserves a memory area for secret injection and includes a pointer to it the in EFI config table entry LINUX_EFI_COCO_SECRET_TABLE_GUID. If EFI exposes such a table entry, uefi_init() will keep a pointer to the EFI config table entry in efi.coco_secret, so it can be used later by the kernel (specifically drivers/virt/coco/efi_secret). It will also appear in the kernel log as "CocoSecret=ADDRESS"; for example: [ 0.000000] efi: EFI v2.70 by EDK II [ 0.000000] efi: CocoSecret=0x7f22e680 SMBIOS=0x7f541000 ACPI=0x7f77e000 ACPI 2.0=0x7f77e014 MEMATTR=0x7ea0c018 The new functionality can be enabled with CONFIG_EFI_COCO_SECRET=y. Signed-off-by: Dov Murik Reviewed-by: Gerd Hoffmann Link: https://lore.kernel.org/r/20220412212127.154182-2-dovmurik@linux.ibm.com Signed-off-by: Ard Biesheuvel --- drivers/firmware/efi/Kconfig | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'drivers/firmware/efi/Kconfig') diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig index 243882f5e5f9..f8ddd2259ba0 100644 --- a/drivers/firmware/efi/Kconfig +++ b/drivers/firmware/efi/Kconfig @@ -299,3 +299,19 @@ config EFI_DISABLE_RUNTIME an issue for Real-Time kernels. This default can be overridden by using the efi=runtime option. + +config EFI_COCO_SECRET + bool "EFI Confidential Computing Secret Area Support" + depends on EFI + help + Confidential Computing platforms (such as AMD SEV) allow the + Guest Owner to securely inject secrets during guest VM launch. + The secrets are placed in a designated EFI reserved memory area. + + In order to use the secrets in the kernel, the location of the secret + area (as published in the EFI config table) must be kept. + + If you say Y here, the address of the EFI secret area will be kept + for usage inside the kernel. This will allow the + virt/coco/efi_secret module to access the secrets, which in turn + allows userspace programs to access the injected secrets. -- cgit v1.2.3-59-g8ed1b