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Subject: Re: [PATCH v12 02/11] mm, swap: Add infrastructure for saving page
 metadata on swap
To: Khalid Aziz <khalid.aziz@oracle.com>, akpm@linux-foundation.org,
        davem@davemloft.net, arnd@arndb.de
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From: Dave Hansen <dave.hansen@linux.intel.com>
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On 03/05/2018 12:28 PM, Khalid Aziz wrote:
>> Do you have a way to tell that data is not being thrown away?  Like if
>> the ADI metadata is different for two different cachelines within a
>> single page?
> 
> Yes, since access to tagged data is made using pointers with ADI tag
> embedded in the top bits, any mismatch between what app thinks the ADI
> tags should be and what is stored in the RAM for corresponding page will
> result in exception. If ADI data gets thrown away, we will get an ADI
> tag mismatch exception. If ADI tags for two different ADI blocks on a
> page are different when app expected them to be the same, we will see an
> exception on access to the block with wrong ADI data.

So, when an app has two different ADI tags on two parts of a page, the
page gets swapped, and the ADI block size is under PAGE_SIZE, the app
will get an ADI exception after swap-in through no fault of its own?