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

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Date:   Mon, 24 Apr 2017 08:57:17 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Tom Lendacky <thomas.lendacky@....com>, 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
Cc:     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>, Borislav Petkov <bp@...en8.de>,
        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 04/24/2017 08:53 AM, Tom Lendacky wrote:
> On 4/21/2017 4:52 PM, Dave Hansen wrote:
>> On 04/18/2017 02:17 PM, Tom Lendacky wrote:
>>> @@ -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
>>
>> It seems wrong to be modifying __va().  It currently takes a physical
>> address, and this modifies it to take a physical address plus the SME
>> bits.
> 
> This actually modifies it to be sure the encryption bit is not part of
> the physical address.

If SME bits make it this far, we have a bug elsewhere.  Right?  Probably
best not to paper over it.