linux-kernel - Re: [PATCH v5 09/32] x86/mm: Provide general kernel support for memory encryption

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Date:   Thu, 4 May 2017 09:34:09 -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>, <kexec@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <kasan-dev@...glegroups.com>,
        <linux-mm@...ck.org>, <iommu@...ts.linux-foundation.org>,
        Rik van Riel <riel@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Larry Woodman <lwoodman@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dave Young <dyoung@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v5 09/32] x86/mm: Provide general kernel support for
 memory encryption



On 4/27/2017 11:12 AM, Borislav Petkov wrote:
> On Tue, Apr 18, 2017 at 04:17:54PM -0500, Tom Lendacky wrote:
>> Changes to the existing page table macros will allow the SME support to
>> be enabled in a simple fashion with minimal changes to files that use these
>> macros.  Since the memory encryption mask will now be part of the regular
>> pagetable macros, we introduce two new macros (_PAGE_TABLE_NOENC and
>> _KERNPG_TABLE_NOENC) to allow for early pagetable creation/initialization
>> without the encryption mask before SME becomes active.  Two new pgprot()
>> macros are defined to allow setting or clearing the page encryption mask.
>
> ...
>
>> @@ -55,7 +57,7 @@ static inline void copy_user_page(void *to, void *from, unsigned long vaddr,
>>  	__phys_addr_symbol(__phys_reloc_hide((unsigned long)(x)))
>>
>>  #ifndef __va
>> -#define __va(x)			((void *)((unsigned long)(x)+PAGE_OFFSET))
>> +#define __va(x)			((void *)(__sme_clr(x) + PAGE_OFFSET))
>>  #endif
>>
>>  #define __boot_va(x)		__va(x)
>> diff --git a/arch/x86/include/asm/page_types.h b/arch/x86/include/asm/page_types.h
>> index 7bd0099..fead0a5 100644
>> --- a/arch/x86/include/asm/page_types.h
>> +++ b/arch/x86/include/asm/page_types.h
>> @@ -15,7 +15,7 @@
>>  #define PUD_PAGE_SIZE		(_AC(1, UL) << PUD_SHIFT)
>>  #define PUD_PAGE_MASK		(~(PUD_PAGE_SIZE-1))
>>
>> -#define __PHYSICAL_MASK		((phys_addr_t)((1ULL << __PHYSICAL_MASK_SHIFT) - 1))
>> +#define __PHYSICAL_MASK		((phys_addr_t)(__sme_clr((1ULL << __PHYSICAL_MASK_SHIFT) - 1)))
>
> That looks strange: poking SME mask hole into a mask...?

I masked it out here based on a previous comment from Dave Hansen:

   http://marc.info/?l=linux-kernel&m=148778719826905&w=2

I could move the __sme_clr into the individual defines of:

PHYSICAL_PAGE_MASK, PHYSICAL_PMD_PAGE_MASK and PHYSICAL_PUD_PAGE_MASK

Either way works for me.

Thanks,
Tom

>
>>  #define __VIRTUAL_MASK		((1UL << __VIRTUAL_MASK_SHIFT) - 1)
>>
>>  /* Cast *PAGE_MASK to a signed type so that it is sign-extended if
>