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Wed, 04 Sep 2024 09:38:35 -0700 (PDT) MIME-Version: 1.0 References: <20240826204353.2228736-1-peterx@redhat.com> <20240828142422.GU3773488@nvidia.com> <20240828234958.GE3773488@nvidia.com> <20240904155203.GJ3915968@nvidia.com> In-Reply-To: <20240904155203.GJ3915968@nvidia.com> From: Jiaqi Yan Date: Wed, 4 Sep 2024 09:38:22 -0700 Message-ID: Subject: Re: [PATCH v2 00/19] mm: Support huge pfnmaps To: Jason Gunthorpe Cc: Peter Xu , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Gavin Shan , Catalin Marinas , x86@kernel.org, Ingo Molnar , Andrew Morton , Paolo Bonzini , Dave Hansen , Thomas Gleixner , Alistair Popple , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Sean Christopherson , Oscar Salvador , Borislav Petkov , Zi Yan , Axel Rasmussen , David Hildenbrand , Yan Zhao , Will Deacon , Kefeng Wang , Alex Williamson , ankita@nvidia.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: A3391A0031 X-Stat-Signature: iosxo3yhht3g76dfzuey3p5fqq8aziaw X-Rspam-User: X-HE-Tag: 1725467917-963844 X-HE-Meta: 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 fisUWVl2 XhJH6hHxhq5j4jqGn8UPmjbAAX043SejsWmuL+ObSSZmT1kus6VJ+p2mMNKlzWZ+C+Gh0pCx5P4eHsutsU9e4iLz+YyfU5Ij3UkBiUfJr+MIMAuTEKCBKU1BgAq96kJWQvcEyzYHXAEGp6OOsq9r0GyED4VJgCx8uhX83fRtwYj4e9FOKO4noRyTbD/y2WvvXnMiGHmL4lrrQx8PpbgZCdilcGvR+EYZW/5qtkgRciDw6R7y0z8XdYvKAW7rtOmGLg1zHHWnw1oCQ5o4= 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 Wed, Sep 4, 2024 at 8:52=E2=80=AFAM Jason Gunthorpe wro= te: > > On Thu, Aug 29, 2024 at 12:21:39PM -0700, Jiaqi Yan wrote: > > > I think we still want to attempt to SIGBUS userspace, regardless of > > doing unmap_mapping_range or not. > > IMHO we need to eliminate this path if we actually want to keep things > mapped. > > There is no way to generate the SIGBUS without poking a 4k hole in the > 1G page, as only that 4k should get SIGBUS, every other byte of the 1G > is clean. Ah, sorry I wasn't clear. The SIGBUS will be only for poisoned PFN; clean PFNs under the same PUD/PMD for sure don't need any SIGBUS, which is the whole purpose of not unmapping. > > Jason