linux-kernel - Re: [RFC PATCH v1 03/18] x86: Secure Memory Encryption (SME) support

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Date:	Wed, 27 Apr 2016 11:20:57 -0500
From:	Tom Lendacky <thomas.lendacky@....com>
To:	Pavel Machek <pavel@....cz>
CC:	<linux-arch@...r.kernel.org>, <linux-efi@...r.kernel.org>,
	<kvm@...r.kernel.org>, <linux-doc@...r.kernel.org>,
	<x86@...nel.org>, <linux-kernel@...r.kernel.org>,
	<kasan-dev@...glegroups.com>, <linux-mm@...ck.org>,
	<iommu@...ts.linux-foundation.org>,
	Radim Krčmář <rkrcmar@...hat.com>,
	Arnd Bergmann <arnd@...db.de>,
	Jonathan Corbet <corbet@....net>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Joerg Roedel <joro@...tes.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	Alexander Potapenko <glider@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [RFC PATCH v1 03/18] x86: Secure Memory Encryption (SME) support

On 03/22/2016 08:03 AM, Pavel Machek wrote:
> On Tue 2016-04-26 17:56:26, Tom Lendacky wrote:
>> Provide support for Secure Memory Encryption (SME). This initial support
>> defines the memory encryption mask as a variable for quick access and an
>> accessor for retrieving the number of physical addressing bits lost if
>> SME is enabled.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
>> ---
>>  arch/x86/include/asm/mem_encrypt.h |   37 ++++++++++++++++++++++++++++++++++++
>>  arch/x86/kernel/Makefile           |    2 ++
>>  arch/x86/kernel/mem_encrypt.S      |   29 ++++++++++++++++++++++++++++
>>  arch/x86/kernel/x8664_ksyms_64.c   |    6 ++++++
>>  4 files changed, 74 insertions(+)
>>  create mode 100644 arch/x86/include/asm/mem_encrypt.h
>>  create mode 100644 arch/x86/kernel/mem_encrypt.S
>>
>> index 0000000..ef7f325
>> --- /dev/null
>> +++ b/arch/x86/kernel/mem_encrypt.S
>> @@ -0,0 +1,29 @@
>> +/*
>> + * AMD Memory Encryption Support
>> + *
>> + * Copyright (C) 2016 Advanced Micro Devices, Inc.
>> + *
>> + * Author: Tom Lendacky <thomas.lendacky@....com>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + */
>> +
>> +#include <linux/linkage.h>
>> +
>> +	.text
>> +	.code64
>> +ENTRY(sme_get_me_loss)
>> +	xor	%rax, %rax
>> +	mov	sme_me_loss(%rip), %al
>> +	ret
>> +ENDPROC(sme_get_me_loss)
> 
> Does this really need to be implemented in assembly?

That particular routine probably doesn't need to be in assembly. But
since it was such a simple routine I put it there because a later
patch derives the value in this file.

Thanks,
Tom

> 
>