linux-kernel - Re: [RFC, PATCH 21/22] x86/mm: Introduce page_keyid() and page

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Message-ID: <91d27559-3f28-d53c-9fd9-d16e015a3f59@intel.com>
Date:   Tue, 6 Mar 2018 06:56:08 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC, PATCH 21/22] x86/mm: Introduce page_keyid() and
 page_encrypted()

On 03/06/2018 12:57 AM, Kirill A. Shutemov wrote:
> On Mon, Mar 05, 2018 at 09:08:53AM -0800, Dave Hansen wrote:
>> On 03/05/2018 08:26 AM, Kirill A. Shutemov wrote:
>>> +static inline bool page_encrypted(struct page *page)
>>> +{
>>> +	/* All pages with non-zero KeyID are encrypted */
>>> +	return page_keyid(page) != 0;
>>> +}
>>
>> Is this true?  I thought there was a KEYID_NO_ENCRYPT "Do not encrypt
>> memory when this KeyID is in use."  Is that really only limited to key 0.
> 
> Well, it depends on what we mean by "encrypted". For memory management
> pruposes we care if the page is encrypted with KeyID different from
> default one. All pages with non-default KeyID threated the same by memory
> management.

Doesn't it really mean "am I able to use the direct map to get this
page's contents?"