linux-kernel - Re: [PATCH v6 5/5] x86/sev: Add SNP-specific unaccepted memory support

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Date:   Fri, 9 Dec 2022 08:18:35 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Michael Roth <michael.roth@....com>,
        Joerg Roedel <jroedel@...e.de>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v6 5/5] x86/sev: Add SNP-specific unaccepted memory
 support

On 12/8/22 16:12, Kirill A. Shutemov wrote:
> On Thu, Dec 08, 2022 at 09:29:13AM -0600, Tom Lendacky wrote:
>> Add SNP-specific hooks to the unaccepted memory support in the boot
>> path (__accept_memory()) and the core kernel (accept_memory()) in order
>> to support booting SNP guests when unaccepted memory is present. Without
>> this support, SNP guests will fail to boot and/or panic() when unaccepted
>> memory is present in the EFI memory map.
>>
>> The process of accepting memory under SNP involves invoking the hypervisor
>> to perform a page state change for the page to private memory and then
>> issuing a PVALIDATE instruction to accept the page.
>>
>> Since the boot path and the core kernel paths perform similar operations,
>> move the pvalidate_pages() and vmgexit_psc() functions into sev-shared.c
>> to avoid code duplication.
>>
>> Create the new header file arch/x86/boot/compressed/sev.h because adding
>> the function declaration to any of the existing SEV related header files
>> pulls in too many other header files, causing the build to fail.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
>> ---
>>   arch/x86/Kconfig                |   1 +
>>   arch/x86/boot/compressed/mem.c  |   3 +
>>   arch/x86/boot/compressed/sev.c  |  54 ++++++++++++++-
>>   arch/x86/boot/compressed/sev.h  |  23 +++++++
>>   arch/x86/include/asm/sev.h      |   3 +
>>   arch/x86/kernel/sev-shared.c    | 103 +++++++++++++++++++++++++++++
>>   arch/x86/kernel/sev.c           | 112 ++++----------------------------
>>   arch/x86/mm/unaccepted_memory.c |   4 ++
>>   8 files changed, 204 insertions(+), 99 deletions(-)
>>   create mode 100644 arch/x86/boot/compressed/sev.h
>>
>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>> index d88f61940aa7..0704d4795919 100644
>> --- a/arch/x86/Kconfig
>> +++ b/arch/x86/Kconfig
>> @@ -1549,6 +1549,7 @@ config AMD_MEM_ENCRYPT
>>   	select INSTRUCTION_DECODER
>>   	select ARCH_HAS_CC_PLATFORM
>>   	select X86_MEM_ENCRYPT
>> +	select UNACCEPTED_MEMORY
>>   	help
>>   	  Say yes to enable support for the encryption of system memory.
>>   	  This requires an AMD processor that supports Secure Memory
> 
> I think it misses "depends on EFI_STUB".

Ah, good catch, thanks. I'll update the series to add that.

Thanks,
Tom

> 
> The code I've submitted contains "select EFI_STUB", but it causes build
> issues for some configurations. I've changed it to "depends on" in git.
>