linux-kernel - Re: [PATCH v7 04/14] mm/shmem: Support memfile

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 14 Jul 2022 07:49:03 +0800
From:   Chao Peng <chao.p.peng@...ux.intel.com>
To:     "Gupta, Pankaj" <pankaj.gupta@....com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-api@...r.kernel.org, linux-doc@...r.kernel.org,
        qemu-devel@...gnu.org, linux-kselftest@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
        Hugh Dickins <hughd@...gle.com>,
        Jeff Layton <jlayton@...nel.org>,
        "J . Bruce Fields" <bfields@...ldses.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>, Mike Rapoport <rppt@...nel.org>,
        Steven Price <steven.price@....com>,
        "Maciej S . Szmigiero" <mail@...iej.szmigiero.name>,
        Vlastimil Babka <vbabka@...e.cz>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        luto@...nel.org, jun.nakajima@...el.com, dave.hansen@...el.com,
        ak@...ux.intel.com, david@...hat.com, aarcange@...hat.com,
        ddutile@...hat.com, dhildenb@...hat.com,
        Quentin Perret <qperret@...gle.com>,
        Michael Roth <michael.roth@....com>, mhocko@...e.com,
        Muchun Song <songmuchun@...edance.com>
Subject: Re: [PATCH v7 04/14] mm/shmem: Support memfile_notifier

On Wed, Jul 13, 2022 at 12:01:13PM +0200, Gupta, Pankaj wrote:
> 
> > > > +#ifdef CONFIG_MIGRATION
> > > > +static int shmem_migrate_page(struct address_space *mapping,
> > > > +			      struct page *newpage, struct page *page,
> > > > +			      enum migrate_mode mode)
> > > > +{
> > > > +	struct inode *inode = mapping->host;
> > > > +	struct shmem_inode_info *info = SHMEM_I(inode);
> > > > +
> > > > +	if (info->memfile_node.flags & MEMFILE_F_UNMOVABLE)
> > > > +		return -EOPNOTSUPP;
> > > > +	return migrate_page(mapping, newpage, page, mode);
> > > 
> > > Wondering how well page migrate would work for private pages
> > > on shmem memfd based backend?
> > 
> >  From high level:
> >    - KVM unset MEMFILE_F_UNMOVABLE bit to indicate it capable of
> >      migrating a page.
> >    - Introduce new 'migrate' callback(s) to memfile_notifier_ops for KVM
> >      to register.
> >    - The callback is hooked to migrate_page() here.
> >    - Once page migration requested, shmem calls into the 'migrate'
> >      callback(s) to perform additional steps for encrypted memory (For
> >      TDX we will call TDH.MEM.PAGE.RELOCATE).
> 
> Yes, that would require additional (protocol specific) handling for private
> pages. Was trying to find where "MEMFILE_F_UNMOVABLE" flag is set currently?

It's set with memfile_register_notifier() in patch 13.

> 
> Thanks,
> Pankaj