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Sun, 19 Apr 2026 10:34:04 -0400 (EDT) Date: Sun, 19 Apr 2026 15:33:58 +0100 From: Kiryl Shutsemau To: "David Hildenbrand (Arm)" Cc: Andrew Morton , Peter Xu , Lorenzo Stoakes , Mike Rapoport , Suren Baghdasaryan , Vlastimil Babka , "Liam R . Howlett" , Zi Yan , Jonathan Corbet , Shuah Khan , Sean Christopherson , Paolo Bonzini , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [RFC, PATCH 00/12] userfaultfd: working set tracking for VM guest memory Message-ID: References: <20260414142354.1465950-1-kas@kernel.org> <55019037-4f1c-4d9c-83ee-3a844d8f3d5e@kernel.org> <1a499781-1115-44bc-adbf-2ac3769354ca@kernel.org> <4c635703-3d8d-4cfa-bb98-7f6f5fcbe547@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: C9154140005 X-Rspamd-Server: rspam07 X-Stat-Signature: kh18cstw4icne5twyydz5agb61sdwj7q X-Rspam-User: X-HE-Tag: 1776609248-469682 X-HE-Meta: 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 fdrI7y7k lt6mmSAHYGhcgyKLCmBAp1z1nLhb5GLql0hfcnYWeDcpg3GhJLxNHznBBbMU4a1zvaNU7G8Mz+t0FgdetoBC9UriVF20/cROcn0LLMHoubY/UqkbjGZ/BCf4azkxga6hO7Zd5Za2VHvet9lDPpw3LTG6Ypg5E6OCbeeTkeC3mCv2jl/hOMxX+Mxc4NSFy8KYeotxsVU49LIRCqUUryetP9H6x8SKF1I0/8EWFEpc1osE7efKxxYvA31tIk2Ze5WF99JJQ2SxYRZWe5b1CKR7qSRQoiERqvoOJvBVMec9/IzVdMXw= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Apr 17, 2026 at 01:26:34PM +0100, Kiryl Shutsemau wrote: > > Leaving NUMA-balancing aside, a simple > > mprotect(PROT_NONE)+mprotect(PROT_READ) would already be problematic to > > distinguish both cases. > > Hm. I didn't consider this case (miss some uffd lore). Will rework to > reuse existing PTE bit. See https://git.kernel.org/pub/scm/linux/kernel/git/kas/linux.git uffd/rfc-v3 -- Kiryl Shutsemau / Kirill A. Shutemov