linux-kernel - Re: [PATCHv6 02/15] mm: Add support for unaccepted memory

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Message-ID: <20220517180419.ysqhiyrsa3jns53p@black.fi.intel.com>
Date:   Tue, 17 May 2022 21:04:19 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Borislav Petkov <bp@...en8.de>, Andy Lutomirski <luto@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Joerg Roedel <jroedel@...e.de>,
        Ard Biesheuvel <ardb@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Tom Lendacky <thomas.lendacky@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Varad Gautam <varad.gautam@...e.com>,
        Dario Faggioli <dfaggioli@...e.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Mike Rapoport <rppt@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        marcelo.cerri@...onical.com, tim.gardner@...onical.com,
        khalid.elmously@...onical.com, philip.cox@...onical.com,
        x86@...nel.org, linux-mm@...ck.org, linux-coco@...ts.linux.dev,
        linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mike Rapoport <rppt@...ux.ibm.com>
Subject: Re: [PATCHv6 02/15] mm: Add support for unaccepted memory

On Tue, May 17, 2022 at 10:45:16AM -0700, Andrew Morton wrote:
> On Tue, 17 May 2022 18:34:31 +0300 "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> wrote:
> 
> > UEFI Specification version 2.9 introduces the concept of memory
> > acceptance. Some Virtual Machine platforms, such as Intel TDX or AMD
> > SEV-SNP, require memory to be accepted before it can be used by the
> > guest. Accepting happens via a protocol specific to the Virtual Machine
> > platform.
> > 
> > ...
> >
> > --- a/include/linux/page-flags.h
> > +++ b/include/linux/page-flags.h
> > @@ -928,6 +928,14 @@ static inline bool is_page_hwpoison(struct page *page)
> >  #define PG_offline	0x00000100
> >  #define PG_table	0x00000200
> >  #define PG_guard	0x00000400
> > +#define PG_unaccepted	0x00000800
> 
> "For pages that are never mapped to userspace (and aren't PageSlab),
> page_type may be used."
> 
> Is that true of these pages?

Yes. PG_unaccepted is never set for any allocated page. It is only set for
pages on free lists. It gets cleared in post_alloc_hook().

-- 
 Kirill A. Shutemov