linux-kernel - Re: [PATCHv7 06/14] efi/x86: Implement support for unaccepted memory

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Message-ID: <Yt+nOeLMqRxjObbx@zn.tnic>
Date:   Tue, 26 Jul 2022 10:35:05 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joerg Roedel <jroedel@...e.de>,
        Ard Biesheuvel <ardb@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Tom Lendacky <thomas.lendacky@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Varad Gautam <varad.gautam@...e.com>,
        Dario Faggioli <dfaggioli@...e.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Mike Rapoport <rppt@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        marcelo.cerri@...onical.com, tim.gardner@...onical.com,
        khalid.elmously@...onical.com, philip.cox@...onical.com,
        x86@...nel.org, linux-mm@...ck.org, linux-coco@...ts.linux.dev,
        linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv7 06/14] efi/x86: Implement support for unaccepted memory

On Tue, Jun 14, 2022 at 03:02:23PM +0300, Kirill A. Shutemov wrote:
> diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
> index 7aa4717cdcac..e1270beff4dc 100644
> --- a/drivers/firmware/efi/Kconfig
> +++ b/drivers/firmware/efi/Kconfig
> @@ -305,6 +305,20 @@ config EFI_COCO_SECRET
>  	  virt/coco/efi_secret module to access the secrets, which in turn
>  	  allows userspace programs to access the injected secrets.
>  
> +config UNACCEPTED_MEMORY
> +	bool
> +	depends on EFI_STUB
> +	help
> +	   Some Virtual Machine platforms, such as Intel TDX, require
> +	   some memory to be "accepted" by the guest before it can be used.
> +	   This mechanism helps prevent malicious hosts from making changes
> +	   to guest memory.
> +
> +	   UEFI specification v2.9 introduced EFI_UNACCEPTED_MEMORY memory type.
> +
> +	   This option adds support for unaccepted memory and makes such memory
> +	   usable by the kernel.
> +

This looks weird:

$ grep EFI_STUB .config
CONFIG_EFI_STUB=y
$ grep UNACCEPTED_MEMORY .config
$

So the bool needs to have a text string after it so that it is
selectable or how is UNACCEPTED_MEMORY supposed to be enabled otherwise?

If I add the string and select UNACCEPTED_MEMORY, it won't build:

mm/page_alloc.c: In function ‘accept_page’:
mm/page_alloc.c:1013:9: error: implicit declaration of function ‘accept_memory’ [-Werror=implicit-function-declaration]
 1013 |         accept_memory(start, start + (PAGE_SIZE << order));
      |         ^~~~~~~~~~~~~
mm/page_alloc.c: In function ‘page_contains_unaccepted’:
mm/page_alloc.c:1029:16: error: implicit declaration of function ‘range_contains_unaccepted_memory’; did you mean ‘page_contains_unaccepted’? [-Werror=implicit-function-declaration]
 1029 |         return range_contains_unaccepted_memory(start, end);
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |                page_contains_unaccepted
mm/memblock.c: In function ‘memblock_alloc_range_nid’:
mm/memblock.c:1415:9: error: implicit declaration of function ‘accept_memory’ [-Werror=implicit-function-declaration]
 1415 |         accept_memory(found, found + size);
      |         ^~~~~~~~~~~~~
cc1: some warnings being treated as errors
make[1]: *** [scripts/Makefile.build:249: mm/memblock.o] Error 1
make[1]: *** Waiting for unfinished jobs....
cc1: some warnings being treated as errors
make[1]: *** [scripts/Makefile.build:249: mm/page_alloc.o] Error 1
make: *** [Makefile:1843: mm] Error 2
make: *** Waiting for unfinished jobs....

so this is weird.

> diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
> index 504955368934..b91c89100b2d 100644
> --- a/drivers/firmware/efi/libstub/x86-stub.c
> +++ b/drivers/firmware/efi/libstub/x86-stub.c
> @@ -15,6 +15,7 @@
>  #include <asm/setup.h>
>  #include <asm/desc.h>
>  #include <asm/boot.h>
> +#include <asm/unaccepted_memory.h>
>  
>  #include "efistub.h"
>  
> @@ -607,6 +608,17 @@ setup_e820(struct boot_params *params, struct setup_data *e820ext, u32 e820ext_s
>  			e820_type = E820_TYPE_PMEM;
>  			break;
>  
> +		case EFI_UNACCEPTED_MEMORY:
> +			if (!IS_ENABLED(CONFIG_UNACCEPTED_MEMORY)) {
> +				efi_warn_once("The system has unaccepted memory,"
> +					     " but kernel does not support it\n");
> +				efi_warn_once("Consider enabling CONFIG_UNACCEPTED_MEMORY\n");
> +				continue;
> +			}

So that it can be grepped for:

diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index b91c89100b2d..8be6b675e08e 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -610,9 +610,8 @@ setup_e820(struct boot_params *params, struct setup_data *e820ext, u32 e820ext_s
 
 		case EFI_UNACCEPTED_MEMORY:
 			if (!IS_ENABLED(CONFIG_UNACCEPTED_MEMORY)) {
-				efi_warn_once("The system has unaccepted memory,"
-					     " but kernel does not support it\n");
-				efi_warn_once("Consider enabling CONFIG_UNACCEPTED_MEMORY\n");
+				efi_warn_once(
+"The system has unaccepted memory, but kernel does not support it.\nConsider enabling CONFIG_UNACCEPTED_MEMORY\n");
 				continue;
 			}
 			e820_type = E820_TYPE_RAM;


Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette