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Message-ID: <7c0844d8-6f97-4904-a140-abeabeb552c1@intel.com>
Date: Tue, 31 Oct 2023 16:35:08 +0800
From: Xiaoyao Li <xiaoyao.li@...el.com>
To: Sean Christopherson <seanjc@...gle.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Marc Zyngier <maz@...nel.org>,
Oliver Upton <oliver.upton@...ux.dev>,
Huacai Chen <chenhuacai@...nel.org>,
Michael Ellerman <mpe@...erman.id.au>,
Anup Patel <anup@...infault.org>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Alexander Viro <viro@...iv.linux.org.uk>,
Christian Brauner <brauner@...nel.org>,
"Matthew Wilcox (Oracle)" <willy@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
kvmarm@...ts.linux.dev, linux-mips@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org, kvm-riscv@...ts.infradead.org,
linux-riscv@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Xu Yilun <yilun.xu@...el.com>,
Chao Peng <chao.p.peng@...ux.intel.com>,
Fuad Tabba <tabba@...gle.com>,
Jarkko Sakkinen <jarkko@...nel.org>,
Anish Moorthy <amoorthy@...gle.com>,
David Matlack <dmatlack@...gle.com>,
Yu Zhang <yu.c.zhang@...ux.intel.com>,
Isaku Yamahata <isaku.yamahata@...el.com>,
Mickaël Salaün <mic@...ikod.net>,
Vlastimil Babka <vbabka@...e.cz>,
Vishal Annapurve <vannapurve@...gle.com>,
Ackerley Tng <ackerleytng@...gle.com>,
Maciej Szmigiero <mail@...iej.szmigiero.name>,
David Hildenbrand <david@...hat.com>,
Quentin Perret <qperret@...gle.com>,
Michael Roth <michael.roth@....com>,
Wang <wei.w.wang@...el.com>,
Liam Merwick <liam.merwick@...cle.com>,
Isaku Yamahata <isaku.yamahata@...il.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH v13 17/35] KVM: Add transparent hugepage support for
dedicated guest memory
On 10/28/2023 2:21 AM, Sean Christopherson wrote:
> Extended guest_memfd to allow backing guest memory with transparent
> hugepages. Require userspace to opt-in via a flag even though there's no
> known/anticipated use case for forcing small pages as THP is optional,
> i.e. to avoid ending up in a situation where userspace is unaware that
> KVM can't provide hugepages.
Personally, it seems not so "transparent" if requiring userspace to opt-in.
People need to 1) check if the kernel built with TRANSPARENT_HUGEPAGE
support, or check is the sysfs of transparent hugepage exists; 2)get the
maximum support hugepage size 3) ensure the size satisfies the
alignment; before opt-in it.
Even simpler, userspace can blindly try to create guest memfd with
transparent hugapage flag. If getting error, fallback to create without
the transparent hugepage flag.
However, it doesn't look transparent to me.
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