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SubjectRe: [PATCH v4 2/3] efi: Reserve confidential computing secret area
On Wed, Oct 20, 2021 at 06:14:07AM +0000, Dov Murik wrote:
> When efi-stub copies an EFI-provided confidential computing (coco)
> secret area, reserve that memory block for future use within the kernel.
>
> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
> ---
> arch/x86/platform/efi/efi.c | 3 +++
> drivers/firmware/efi/Makefile | 1 +
> drivers/firmware/efi/coco.c | 41 +++++++++++++++++++++++++++++++++++
> drivers/firmware/efi/efi.c | 8 +++++++
> include/linux/efi.h | 10 +++++++++
> 5 files changed, 63 insertions(+)
> create mode 100644 drivers/firmware/efi/coco.c
>
> diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
> index 147c30a81f15..1591d67e0bcd 100644
> --- a/arch/x86/platform/efi/efi.c
> +++ b/arch/x86/platform/efi/efi.c
> @@ -93,6 +93,9 @@ static const unsigned long * const efi_tables[] = {
> #ifdef CONFIG_LOAD_UEFI_KEYS
> &efi.mokvar_table,
> #endif
> +#ifdef CONFIG_EFI_COCO_SECRET
> + &efi.coco_secret,
> +#endif
> };
>
> u64 efi_setup; /* efi setup_data physical address */
> diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile
> index c02ff25dd477..49c4a8c0bfc4 100644
> --- a/drivers/firmware/efi/Makefile
> +++ b/drivers/firmware/efi/Makefile
> @@ -32,6 +32,7 @@ obj-$(CONFIG_APPLE_PROPERTIES) += apple-properties.o
> obj-$(CONFIG_EFI_RCI2_TABLE) += rci2-table.o
> obj-$(CONFIG_EFI_EMBEDDED_FIRMWARE) += embedded-firmware.o
> obj-$(CONFIG_LOAD_UEFI_KEYS) += mokvar-table.o
> +obj-$(CONFIG_EFI_COCO_SECRET) += coco.o
>
> fake_map-y += fake_mem.o
> fake_map-$(CONFIG_X86) += x86_fake_mem.o
> diff --git a/drivers/firmware/efi/coco.c b/drivers/firmware/efi/coco.c
> new file mode 100644
> index 000000000000..42f477d6188c
> --- /dev/null
> +++ b/drivers/firmware/efi/coco.c
> @@ -0,0 +1,41 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Confidential computing (coco) secret area handling
> + *
> + * Copyright (C) 2021 IBM Corporation
> + * Author: Dov Murik <dovmurik@linux.ibm.com>
> + */
> +
> +#define pr_fmt(fmt) "efi: " fmt
> +
> +#include <linux/efi.h>
> +#include <linux/init.h>
> +#include <linux/memblock.h>
> +#include <asm/early_ioremap.h>
> +
> +/*
> + * Reserve the confidential computing secret area memory
> + */
> +int __init efi_coco_secret_area_reserve(void)
> +{
> + struct linux_efi_coco_secret_area *secret_area;
> + unsigned long secret_area_size;
> +
> + if (efi.coco_secret == EFI_INVALID_TABLE_ADDR)
> + return 0;
> +
> + secret_area = early_memremap(efi.coco_secret, sizeof(*secret_area));
> + if (!secret_area) {
> + pr_err("Failed to map confidential computing secret area\n");
> + efi.coco_secret = EFI_INVALID_TABLE_ADDR;
> + return -ENOMEM;
> + }
> +
> + secret_area_size = sizeof(*secret_area) + secret_area->size;
> + memblock_reserve(efi.coco_secret, secret_area_size);
> +
> + pr_info("Reserved memory of EFI-provided confidential computing secret area");
When kernel code works properly, it is quiet. Why do you need to print
this out at every boot?

> +
> + early_memunmap(secret_area, sizeof(*secret_area));
> + return 0;
> +}

And again, when is this memory freed when shutting down?

thanks,

greg k-h

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