linux-kernel - Re: [RFC PATCH v2 07/20] x86: Provide general kernel support for memory encryption

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Message-ID: <74f3288f-afc7-2170-89ff-a0334451da82@amd.com>
Date:   Wed, 7 Sep 2016 09:19:36 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Borislav Petkov <bp@...en8.de>
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>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Alexander Potapenko <glider@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [RFC PATCH v2 07/20] x86: Provide general kernel support for
 memory encryption

On 09/05/2016 10:22 AM, Borislav Petkov wrote:
> On Mon, Aug 22, 2016 at 05:36:46PM -0500, Tom Lendacky wrote:
>> Adding general kernel support for memory encryption includes:
>> - Modify and create some page table macros to include the Secure Memory
>>   Encryption (SME) memory encryption mask
>> - Update kernel boot support to call an SME routine that checks for and
>>   sets the SME capability (the SME routine will grow later and for now
>>   is just a stub routine)
>> - Update kernel boot support to call an SME routine that encrypts the
>>   kernel (the SME routine will grow later and for now is just a stub
>>   routine)
>> - Provide an SME initialization routine to update the protection map with
>>   the memory encryption mask so that it is used by default
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> 
> ...
> 
>> diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
>> index c98a559..30f7715 100644
>> --- a/arch/x86/kernel/head_64.S
>> +++ b/arch/x86/kernel/head_64.S
>> @@ -95,6 +95,13 @@ startup_64:
>>  	jnz	bad_address
>>  
>>  	/*
>> +	 * Enable memory encryption (if available). Add the memory encryption
>> +	 * mask to %rbp to include it in the the page table fixup.
>> +	 */
>> +	call	sme_enable
>> +	addq	sme_me_mask(%rip), %rbp
>> +
>> +	/*
>>  	 * Fixup the physical addresses in the page table
>>  	 */
>>  	addq	%rbp, early_level4_pgt + (L4_START_KERNEL*8)(%rip)
>> @@ -116,7 +123,8 @@ startup_64:
>>  	movq	%rdi, %rax
>>  	shrq	$PGDIR_SHIFT, %rax
>>  
>> -	leaq	(4096 + _KERNPG_TABLE)(%rbx), %rdx
>> +	leaq	(4096 + __KERNPG_TABLE)(%rbx), %rdx
>> +	addq	sme_me_mask(%rip), %rdx		/* Apply mem encryption mask */
> 
> Please add comments over the line and not at the side...

Ok, will do.

Thanks,
Tom

>