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AJvYcCV4qUtGqcs7f2i4J0mBQwdZ7xnH+ED95plaCPzJ7bp+jVhlrgLY1IH/uxkCalTGDK+iTayzL6cCzYB/z38K@vger.kernel.org X-Gm-Message-State: AOJu0YwUP+93JVK2oBzuwBt3clB7UrQzk6wWX1eNy1lkfD4yTrXTKNVE QtR86GBvpEvpZfbUWxGFA4E0uS56OE4jbiKB10QIC/C4TcDZUNuYdNGv7U6SxgdRoIFG7s3/ezj 0I5SFH8sGXXTSfUrahIdkTTFnsg== X-Google-Smtp-Source: AGHT+IHjj8hb/RVvZ0IOpTAd6gcfF67ZbXjAX68CTThBkFnrnLTw7dIsH6cNRpPgLu+DDO0Lal4k3FXkbzgyillaoQ== X-Received: from pffl14.prod.google.com ([2002:a62:be0e:0:b0:73e:1cf2:cd5c]) (user=ackerleytng job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:c8d:b0:740:6f69:f52a with SMTP id d2e1a72fcca58-742a9616b19mr4851938b3a.0.1747404448303; Fri, 16 May 2025 07:07:28 -0700 (PDT) Date: Fri, 16 May 2025 07:07:27 -0700 In-Reply-To: (message from Ackerley Tng on Wed, 14 May 2025 16:42:08 -0700) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Message-ID: Subject: Re: [RFC PATCH v2 29/51] mm: guestmem_hugetlb: Wrap HugeTLB as an allocator for guest_memfd From: Ackerley Tng To: Ackerley Tng Cc: kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org, linux-fsdevel@vger.kernel.org, aik@amd.com, ajones@ventanamicro.com, akpm@linux-foundation.org, amoorthy@google.com, anthony.yznaga@oracle.com, anup@brainfault.org, aou@eecs.berkeley.edu, bfoster@redhat.com, binbin.wu@linux.intel.com, brauner@kernel.org, catalin.marinas@arm.com, chao.p.peng@intel.com, chenhuacai@kernel.org, dave.hansen@intel.com, david@redhat.com, dmatlack@google.com, dwmw@amazon.co.uk, erdemaktas@google.com, fan.du@intel.com, fvdl@google.com, graf@amazon.com, haibo1.xu@intel.com, hch@infradead.org, hughd@google.com, ira.weiny@intel.com, isaku.yamahata@intel.com, jack@suse.cz, james.morse@arm.com, jarkko@kernel.org, jgg@ziepe.ca, jgowans@amazon.com, jhubbard@nvidia.com, jroedel@suse.de, jthoughton@google.com, jun.miao@intel.com, kai.huang@intel.com, keirf@google.com, kent.overstreet@linux.dev, kirill.shutemov@intel.com, liam.merwick@oracle.com, maciej.wieczor-retman@intel.com, mail@maciej.szmigiero.name, maz@kernel.org, mic@digikod.net, michael.roth@amd.com, mpe@ellerman.id.au, muchun.song@linux.dev, nikunj@amd.com, nsaenz@amazon.es, oliver.upton@linux.dev, palmer@dabbelt.com, pankaj.gupta@amd.com, paul.walmsley@sifive.com, pbonzini@redhat.com, pdurrant@amazon.co.uk, peterx@redhat.com, pgonda@google.com, pvorel@suse.cz, qperret@google.com, quic_cvanscha@quicinc.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, quic_svaddagi@quicinc.com, quic_tsoni@quicinc.com, richard.weiyang@gmail.com, rick.p.edgecombe@intel.com, rientjes@google.com, roypat@amazon.co.uk, rppt@kernel.org, seanjc@google.com, shuah@kernel.org, steven.price@arm.com, steven.sistare@oracle.com, suzuki.poulose@arm.com, tabba@google.com, thomas.lendacky@amd.com, usama.arif@bytedance.com, vannapurve@google.com, vbabka@suse.cz, viro@zeniv.linux.org.uk, vkuznets@redhat.com, wei.w.wang@intel.com, will@kernel.org, willy@infradead.org, xiaoyao.li@intel.com, yan.y.zhao@intel.com, yilun.xu@intel.com, yuzenghui@huawei.com, zhiquan1.li@intel.com Content-Type: text/plain; charset="UTF-8" Ackerley Tng writes: > guestmem_hugetlb is an allocator for guest_memfd. It wraps HugeTLB to > provide huge folios for guest_memfd. > > This patch also introduces guestmem_allocator_operations as a set of > operations that allocators for guest_memfd can provide. In a later > patch, guest_memfd will use these operations to manage pages from an > allocator. > > The allocator operations are memory-management specific and are placed > in mm/ so key mm-specific functions do not have to be exposed > unnecessarily. > > Signed-off-by: Ackerley Tng > > Change-Id: I3cafe111ea7b3c84755d7112ff8f8c541c11136d > --- > include/linux/guestmem.h | 20 +++++ > include/uapi/linux/guestmem.h | 29 +++++++ > mm/Kconfig | 5 +- > mm/guestmem_hugetlb.c | 159 ++++++++++++++++++++++++++++++++++ > 4 files changed, 212 insertions(+), 1 deletion(-) > create mode 100644 include/linux/guestmem.h > create mode 100644 include/uapi/linux/guestmem.h > > > > diff --git a/mm/Kconfig b/mm/Kconfig > index 131adc49f58d..bb6e39e37245 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -1218,7 +1218,10 @@ config SECRETMEM > > config GUESTMEM_HUGETLB > bool "Enable guestmem_hugetlb allocator for guest_memfd" > - depends on HUGETLBFS > + select GUESTMEM > + select HUGETLBFS > + select HUGETLB_PAGE > + select HUGETLB_PAGE_OPTIMIZE_VMEMMAP My bad. I left out CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y in my testing and just found that when it is set, I hit BUG_ON(pte_page(ptep_get(pte)) != walk->reuse_page); with the basic guest_memfd_test on splitting pages on allocation. I'll follow up with the fix soon. Another note about testing: I've been testing in a nested VM for the development process: 1. Host 2. VM for development 3. Nested VM running kernel being developed 4. Nested nested VMs created during selftests This series has not yet been tested on a physical host. > help > Enable this to make HugeTLB folios available to guest_memfd > (KVM virtualization) as backing memory. > > >