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Howlett" , Asahi Lina , linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, iommu@lists.linux.dev, linux-mm@kvack.org Subject: Re: [PATCH v3] io: add io_pgtable abstraction Message-ID: <20251119095934.28624652@fedora> In-Reply-To: References: <20251112-io-pgtable-v3-1-b00c2e6b951a@google.com> <8A5C6836-992B-477A-A77C-EE0736166552@collabora.com> Organization: Collabora X-Mailer: Claws Mail 4.3.1 (GTK 3.24.51; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: CC3EB20002 X-Stat-Signature: phyjt37jd5smnismqybih4pth1rcxwok X-Rspam-User: X-HE-Tag: 1763542781-392623 X-HE-Meta: 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 KJOOG3hl QZ5rMos7RSZEQz6JPDtUJZENRpFqzDGJequKwRpPY7iqXxtELZF9+g9dt9jFeYhtN90cYIwMx2hX5yoEPT08kmDEvzVlDi0FRSLYbyPjXzaejj1JAkRI5HlGZoTf8btir+Tc00QqlV9zsZivokqb3bZZD9+Mj2c2rQiBSYyUWgp+ZKIdTzjNQWHF8JuU2dqweTP/hw8j+cO7dPalZ1GnefzwBQAOWfMCye+AB9xyl7Qq3DMEhi1u3H13GeXNxGLC6gfqczkm8HNuG8Gy+VyKmk8X2vLWCSX1oJTxDQCIxv3rDIGXtl5n/rG7UXkhyoiKEV0xiZBL1r5cusyYBnHxwE8E1GIonefFck/y2tXMO2kMT3IbvjFTiQij1z/ML73tL9mUFncW7Pe1RWbYqRFcPns3/6MnDc6duSbThBqQUg+Zsrp2R/TW3MXGOhPHfxeOkDrnI6mPWcSWKUGY= 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: On Mon, 17 Nov 2025 16:34:06 +0000 Alice Ryhl wrote: > On Wed, Nov 12, 2025 at 09:57:09AM -0300, Daniel Almeida wrote: > > Hi Alice, > > > > > On 12 Nov 2025, at 07:15, Alice Ryhl wrote: > > > + /// Map a physically contiguous range of pages of the same size. > > > + /// > > > + /// # Safety > > > + /// > > > + /// * This page table must not contain any mapping that overlaps with the mapping created by > > > + /// this call. > > > > I don't think there is a restriction that forbids you from mapping a region that has already been mapped. > > > > If A->B->C are adjacent regions, and you try to map A -> C when B->C is already mapped, I think this > > call will simply return length(A->B). > > I think that such overlapping ranges are not allowed. It triggers a > warn: > > } else if (pte) { > /* We require an unmap first */ > WARN_ON(!(cfg->quirks & IO_PGTABLE_QUIRK_NO_WARN)); > return -EEXIST; I confirm the io_pgtable framework (or at least some of its implementations) doesn't allow you to do that (remap without an explicit unmap coming first).