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Mon, 12 Jan 2026 02:20:26 -0800 (PST) MIME-Version: 1.0 References: <20260109171805.901995-1-smostafa@google.com> <20260109171805.901995-4-smostafa@google.com> <20260109195111.GQ545276@ziepe.ca> In-Reply-To: <20260109195111.GQ545276@ziepe.ca> From: Mostafa Saleh Date: Mon, 12 Jan 2026 10:20:14 +0000 X-Gm-Features: AZwV_QhBZadnJiyUFvTjuypzRI_tAKalJjtR7zhOZQkOyHcxgKv9-680wPv8WNg Message-ID: Subject: Re: [PATCH v6 3/4] iommu: debug-pagealloc: Track IOMMU pages To: Jason Gunthorpe Cc: linux-mm@kvack.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, corbet@lwn.net, joro@8bytes.org, will@kernel.org, robin.murphy@arm.com, akpm@linux-foundation.org, vbabka@suse.cz, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, david@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, xiaqinxin@huawei.com, baolu.lu@linux.intel.com, rdunlap@infradead.org, Samiullah Khawaja Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 5D037180007 X-Stat-Signature: yif3zrnqj8gy5esotmdozhypjogb9htk X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1768213227-75238 X-HE-Meta: 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 KrFDMNFf mbfNrmz3pPa0jcdeilA/6H2xSU6mZNT0gG7gJ6PTseN3qmJCfroPfF/Zzwkdd/ALgErSYVvOZ9sty13u9GKs04QoShyVmCMR4q3aBXByvLFt4N2AHOkiKhEUdqPEKRKet1tmGsCHK5VtlvEv+6ln2TkiIX+vHnbe7i5QGJgpnv2KB6lI18NT1Ysq9aykQ6klk0VSMl9Tsmlf+UNStPJ1tKwUQgTucLVrcJQukqj8AmPi+EJqnlcC4Y3aU/30TDi2U5uxsuBP+jOdoiCtRuON+7XIrkvG+rERhrwMwITE1SoTWFJs= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000135, 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 Fri, Jan 9, 2026 at 7:51=E2=80=AFPM Jason Gunthorpe wrote= : > > On Fri, Jan 09, 2026 at 05:18:04PM +0000, Mostafa Saleh wrote: > > +static struct page_ext *get_iommu_page_ext(phys_addr_t phys) > > +{ > > + struct page *page =3D phys_to_page(phys); > > + struct page_ext *page_ext =3D page_ext_get(page); > > + > > + return page_ext; > > +} > > + > > +static struct iommu_debug_metadata *get_iommu_data(struct page_ext *pa= ge_ext) > > +{ > > + return page_ext_data(page_ext, &page_iommu_debug_ops); > > +} > > + > > +static void iommu_debug_inc_page(phys_addr_t phys) > > +{ > > + struct page_ext *page_ext =3D get_iommu_page_ext(phys); > > + struct iommu_debug_metadata *d =3D get_iommu_data(page_ext); > > You cannot do this - phys_to_page() can only be called if we already > know that phys is a struct page backed item and by the time you get > here that information is lost. > > Probably the only way to resolve this is to somehow pass in an iommu > prot flag that can tell the difference between struct page and > non-struct page addresses. > > But I have to NAK this approach of blindly calling phys_to_page(). > The callers to this, first will check "pfn_valid", which is the right check AFAICT (looking at similar patterns in page_owner for example). Thanks, Mostafa > Jason >