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

From: Tom Lendacky <thomas.lendacky@amd.com>
To: Borislav Petkov <bp@alien8.de>
Cc: linux-arch@vger.kernel.org, linux-efi@vger.kernel.org,
	kvm@vger.kernel.org, linux-doc@vger.kernel.org, x86@kernel.org,
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	"Rik van Riel" <riel@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
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	"Arnd Bergmann" <arnd@arndb.de>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Matt Fleming" <matt@codeblueprint.co.uk>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	"Joerg Roedel" <joro@8bytes.org>,
	"Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
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	"Andy Lutomirski" <luto@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"Andrey Ryabinin" <aryabinin@virtuozzo.com>,
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	"Dave Young" <dyoung@redhat.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Dmitry Vyukov" <dvyukov@google.com>
Subject: Re: [PATCH v5 09/32] x86/mm: Provide general kernel support for memory encryption
Date: Thu, 4 May 2017 09:34:09 -0500	[thread overview]
Message-ID: <0b6e4055-8e07-3a71-3d52-12b0395c8f04@amd.com> (raw)
In-Reply-To: <20170427161227.c57dkvghz63pvmu2@pd.tnic>

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
>