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Fri, 23 Jan 2026 16:07:58 -0800 (PST) Received: from 176938342045 named unknown by gmailapi.google.com with HTTPREST; Fri, 23 Jan 2026 16:07:57 -0800 Received: from 176938342045 named unknown by gmailapi.google.com with HTTPREST; Fri, 23 Jan 2026 16:07:57 -0800 From: Ackerley Tng In-Reply-To: References: MIME-Version: 1.0 Date: Fri, 23 Jan 2026 16:07:57 -0800 X-Gm-Features: AZwV_QiZSx8uXBlkjUzf-XEIBRHwTGQ0-9_ksNxOa1FVccYAoX0KqqZc1VcdbW4 Message-ID: Subject: Re: [RFC PATCH v2 00/51] 1G page support for guest_memfd To: kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org, linux-fsdevel@vger.kernel.org Cc: david@kernel.org, fvdl@google.com, ira.weiny@intel.com, jthoughton@google.com, michael.roth@amd.com, pankaj.gupta@amd.com, rick.p.edgecombe@intel.com, seanjc@google.com, vannapurve@google.com, yan.y.zhao@intel.com, "Kalyazin, Nikita" Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: DCD971C0008 X-Stat-Signature: nc4duc56x39a1ixtej3c5ru6zhyo5bcc X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1769213279-17844 X-HE-Meta: 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 Kbooh6+P m+BWR+4kAhO8x/1PmambNw8QzNBuH5D9I361bPTIRMYGrxjh6gMw4jcvk7DFtDJ7Z+sNqvQaH824NWlFXBUz5hkkwLp5ONyY7t+T3WiOI/SYJ9GmKq3Yd0hqChL9pdThW7Yb357OIVj+dp6YsGFOKiFnIP721cu0Q/u22QXEbMb0i0HzekYPjyl7qSSaNfOvy+ZTGEvZzjj6Y0qippJNwryvzv6hiLKXwXMm/Ayk5XFqN9nYthe+HmriSuBZCPghpWdOrUCpO/YSYLNvRNCnd6CegCTfRNLkamqI9KoDEzi0Fe3pgebpfW98qxLMyH4rKzC5SgtAMGmBpiFR8w+qrXsxVQkBJzXcYsV5w22br8PA/vmCg3EeYtnid0nn5T2OMRtfxwPchRgd/FgJJim0ZPoGKWg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Ackerley Tng writes: Re-using this thread to collect discussions related to guest_memfd HugeTLB support, also trimmed cc list. Here's the latest public version Vishal and I have: https://github.com/googleprodkernel/linux-cc/tree/wip-gmem-conversions-hugetlb-restructuring-12-08-25 On the guest_memfd call on 2026-01-22, Michael found another bug to do with multiple threads trying to allocate within the same huge page at the same time. The fix we're using to make progress is to use hugetlb_fault_mutex_lock. unsigned int gmem_hugetlb_mapping_index_lock(struct address_space *mapping, pgoff_t index, u8 page_order) { pgoff_t index_floor = round_down(index, 1ULL << page_order); return hugetlb_fault_mutex_lock(mapping, index_floor); } void gmem_hugetlb_mapping_index_unlock(unsigned int hash) { hugetlb_fault_mutex_unlock(hash); } and then static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index) { ... declarations ... if (gmem_is_hugetlb(gi->flags)) lock_id = gmem_hugetlb_mapping_index_lock(mapping, index, gi->page_order); ... and this right at the end ... if (gmem_is_hugetlb(gi->flags)) gmem_hugetlb_mapping_index_unlock(lock_id); } Yan also found some bugs (thanks!) and there's a discussion at [*]. [*] https://lore.kernel.org/all/CAEvNRgGG+xYhsz62foOrTeAxUCYxpCKCJnNgTAMYMV=w2eq+6Q@mail.gmail.com/