linux-kernel - Re: [RFC PATCH v2 35/51] mm: guestmem_hugetlb: Add support for splitting and merging pages

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] [day] [month] [year] [list]

Message-ID: <aN_1lSZJKBKvU9gV@google.com>
Date: Fri, 3 Oct 2025 09:11:01 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Ackerley Tng <ackerleytng@...gle.com>
Cc: kvm@...r.kernel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	x86@...nel.org, linux-fsdevel@...r.kernel.org, aik@....com, 
	ajones@...tanamicro.com, akpm@...ux-foundation.org, amoorthy@...gle.com, 
	anthony.yznaga@...cle.com, anup@...infault.org, aou@...s.berkeley.edu, 
	bfoster@...hat.com, binbin.wu@...ux.intel.com, brauner@...nel.org, 
	catalin.marinas@....com, chao.p.peng@...el.com, chenhuacai@...nel.org, 
	dave.hansen@...el.com, david@...hat.com, dmatlack@...gle.com, 
	dwmw@...zon.co.uk, erdemaktas@...gle.com, fan.du@...el.com, fvdl@...gle.com, 
	graf@...zon.com, haibo1.xu@...el.com, hch@...radead.org, hughd@...gle.com, 
	ira.weiny@...el.com, isaku.yamahata@...el.com, jack@...e.cz, 
	james.morse@....com, jarkko@...nel.org, jgg@...pe.ca, jgowans@...zon.com, 
	jhubbard@...dia.com, jroedel@...e.de, jthoughton@...gle.com, 
	jun.miao@...el.com, kai.huang@...el.com, keirf@...gle.com, 
	kent.overstreet@...ux.dev, kirill.shutemov@...el.com, liam.merwick@...cle.com, 
	maciej.wieczor-retman@...el.com, mail@...iej.szmigiero.name, maz@...nel.org, 
	mic@...ikod.net, michael.roth@....com, mpe@...erman.id.au, 
	muchun.song@...ux.dev, nikunj@....com, nsaenz@...zon.es, 
	oliver.upton@...ux.dev, palmer@...belt.com, pankaj.gupta@....com, 
	paul.walmsley@...ive.com, pbonzini@...hat.com, pdurrant@...zon.co.uk, 
	peterx@...hat.com, pgonda@...gle.com, pvorel@...e.cz, qperret@...gle.com, 
	quic_cvanscha@...cinc.com, quic_eberman@...cinc.com, 
	quic_mnalajal@...cinc.com, quic_pderrin@...cinc.com, quic_pheragu@...cinc.com, 
	quic_svaddagi@...cinc.com, quic_tsoni@...cinc.com, richard.weiyang@...il.com, 
	rick.p.edgecombe@...el.com, rientjes@...gle.com, roypat@...zon.co.uk, 
	rppt@...nel.org, shuah@...nel.org, steven.price@....com, 
	steven.sistare@...cle.com, suzuki.poulose@....com, tabba@...gle.com, 
	thomas.lendacky@....com, usama.arif@...edance.com, vannapurve@...gle.com, 
	vbabka@...e.cz, viro@...iv.linux.org.uk, vkuznets@...hat.com, 
	wei.w.wang@...el.com, will@...nel.org, willy@...radead.org, 
	xiaoyao.li@...el.com, yan.y.zhao@...el.com, yilun.xu@...el.com, 
	yuzenghui@...wei.com, zhiquan1.li@...el.com
Subject: Re: [RFC PATCH v2 35/51] mm: guestmem_hugetlb: Add support for
 splitting and merging pages

On Wed, May 14, 2025, Ackerley Tng wrote:
>  const struct guestmem_allocator_operations guestmem_hugetlb_ops = {
>  	.inode_setup = guestmem_hugetlb_setup,
>  	.inode_teardown = guestmem_hugetlb_teardown,
>  	.alloc_folio = guestmem_hugetlb_alloc_folio,
> +	.split_folio = guestmem_hugetlb_split_folio,
> +	.merge_folio = guestmem_hugetlb_merge_folio,
> +	.free_folio = guestmem_hugetlb_free_folio,
>  	.nr_pages_in_folio = guestmem_hugetlb_nr_pages_in_folio,
>  };
>  EXPORT_SYMBOL_GPL(guestmem_hugetlb_ops);

Don't bury exports in an "ops" like this.  Be very explicit in what is exported.
_If_ KVM needs a layer of indirection to support multiple, custom guest_memfd
allocators, then KVM can wire up ops as above.  Indirectly exporting core mm/
functionality via an ops structure like this is unnecessarily sneaky.