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Fri, 31 Jan 2025 03:08:48 -0800 (PST) MIME-Version: 1.0 References: <20250129124034.2612562-1-jackmanb@google.com> In-Reply-To: From: Brendan Jackman Date: Fri, 31 Jan 2025 12:08:37 +0100 X-Gm-Features: AWEUYZlEvY_xcHjwNW-ezz0qbzos3rBRHAhT7troSb_9HZKkR3m94pMkyJkb_gE Message-ID: Subject: Re: [LSF/MM/BPF TOPIC] Page allocation for ASI To: lsf-pc@lists.linux-foundation.org Cc: linux-mm@kvack.org, Andrew Morton , Mel Gorman , David Hildenbrand , Vlastimil Babka , Michal Hocko , Johannes Weiner Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: C5FD21C0003 X-Rspamd-Server: rspam10 X-Stat-Signature: cqzzsypqwbbci8yogors45497mzon9ip X-HE-Tag: 1738321729-524092 X-HE-Meta: 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 ueF9hM1g 1FykXt0VBP0v6qmjJ1OONCtcL9uXTLYQw74cjSJIPoEoTETkjUfytF4XPnCUQDa2HkgI7cZQVQQa08CgJWcJ4HhC2XrfNsjBBy3DCqBm9+OUlscXM8+llV7XxmOy48BgtEnpmQ1sF/C6A/gywyCmn5Y80r30SO4i3nXRvKQ9cUEeQ1ZQSrUeWJriPzzhVCqJqzL7oHD1qZn+E70stx9rqrIhT4Hvdh0y7oOcnyITRP/SMuiwNkTGEJLxQq13iiNLrA9/K2P2vER31DzI= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000050, 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 Wed, 29 Jan 2025 at 17:35, Brendan Jackman wrote: > > On Wed, 29 Jan 2025 at 13:40, Brendan Jackman wrote= : > > - Can we totally avoid the need to allocate pagetables during allocatio= n, by > > keeping ASI=E2=80=99s restricted copy of the physmap in-sync with the= unrestricted one, > > different only in _PAGE_PRESENT? Er, doing that specifically (relying on _PAGE_PRESENT) would be a bad idea, I forgot how broken the old CPUs are, this would probably let you exploit L1TF or something. We would have to munge the PFN too. Anyway as long as we only have to do that at the leaf pagetable, I think the idea still works, we can actually just make the entry pmd_none().