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b=oWSMkeEziLzsMhyEQr+UK97S9luMDwyWNVRrH+XzbhgHPvSuA3m5VS6+J8auQIGEc PdjlS4ykBGjKHM3phiQQCUjWphpTKqYeFFY1k4UGdCHRjAnnlEbYIUsRhL8tp2b0cM lryaa72GaIK7Xyi9o+rV7u8w0A/vPvDP7WX0hGCC4HBdiunMjfc6Wq2KV2zWWIMX+c a2+i1bF3bVS2Oh41uoThrsQDbZP7q4GkiE+mcAmE5N+3JAIq7r2Zlpt9q5gHH+1trM ztiKDX3w+JWkxm6N1L4CN3cyvCwaglxI1rhXAdILefnNe+7Sp+2OGuTONTaDvEyBqE qdVaPbrSZx8+A== Date: Thu, 13 Nov 2025 11:00:15 +0000 From: Will Deacon To: Mostafa Saleh 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, 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, Qinxin Xia Subject: Re: [PATCH v2 2/4] drivers/iommu: Add calls for IOMMU_DEBUG_PAGEALLOC Message-ID: References: <20251106163953.1971067-1-smostafa@google.com> <20251106163953.1971067-3-smostafa@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251106163953.1971067-3-smostafa@google.com> X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 983F84001B X-Stat-Signature: 3wb9a6cw94sncms6j16wr66gbe8j8jms X-Rspam-User: X-HE-Tag: 1763031623-722843 X-HE-Meta: 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 jDVEOSbR Q2aTclfd7jdvfXODI2TlVGgkSYw1PPNIi7ovdE02OpTYsFphXmlAiSet4haaHc7/s5FPdjpa3oz8zUc3nm8f16zCiX+Pz9+a/ymoJw2MnUrnpONlBpgr7ab+C4bio1NrmjHtM3JDuZPlwKkC7fiEXH1cbH7t3P39Jmr3ywrTJYlJQAb4UvxJ350P6vxYgiD4bzfsNdfUy4f5+vdxsmnc0w7scHykhTWhzdojpx6dCQiembIgjwF1HG8/Wjn/ztbG2T2h3oO0PlevqYWrIHCLRjoe4wDvDbJzFmVOpTe6svfpYhhuj9UIoSQcEmg== 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 Thu, Nov 06, 2025 at 04:39:51PM +0000, Mostafa Saleh wrote: > Add calls for the new iommu debug config IOMMU_DEBUG_PAGEALLOC: > - iommu_debug_init: Enable the debug mode if configured by the user. > - iommu_debug_map: Track iommu pages mapped, using physical address. > - iommu_debug_unmap: Track iommu pages unmapped, using IO virtual > address. > - iommu_debug_remap: Track iommu pages, already mapped using IOVA. > > We have to do the unmap/remap as once pages are unmapped we lose the > information of the physical address. > This is racy, but the API is racy by construction as it uses refcounts > and doesn't attempt to lock/synchronize with the IOMMU API as that will > be costly, meaning that possibility of false negative exists. > > Signed-off-by: Mostafa Saleh > Tested-by: Qinxin Xia > --- > drivers/iommu/iommu-debug-pagealloc.c | 23 ++++++++++++ > drivers/iommu/iommu.c | 14 ++++++- > include/linux/iommu-debug-pagealloc.h | 54 +++++++++++++++++++++++++++ > 3 files changed, 89 insertions(+), 2 deletions(-) > > diff --git a/drivers/iommu/iommu-debug-pagealloc.c b/drivers/iommu/iommu-debug-pagealloc.c > index 385c8bfae02b..a6a2f844b09d 100644 > --- a/drivers/iommu/iommu-debug-pagealloc.c > +++ b/drivers/iommu/iommu-debug-pagealloc.c > @@ -5,11 +5,13 @@ > * IOMMU API debug page alloc sanitizer > */ > #include > +#include > #include > #include > #include > > static bool needed; > +DEFINE_STATIC_KEY_FALSE(iommu_debug_initialized); > > struct iommu_debug_metadate { > atomic_t ref; > @@ -25,6 +27,27 @@ struct page_ext_operations page_iommu_debug_ops = { > .need = need_iommu_debug, > }; > > +void __iommu_debug_map(struct iommu_domain *domain, phys_addr_t phys, size_t size) > +{ > +} > + > +void __iommu_debug_unmap(struct iommu_domain *domain, unsigned long iova, size_t size) > +{ > +} > + > +void __iommu_debug_remap(struct iommu_domain *domain, unsigned long iova, size_t size) > +{ > +} Since the IOMMU API doesn't really have a "remap" operation, I wonder whether it would be clearer to have unmap_begin() and unmap_end() functions instead? You'd probably want to call them as a pair, so the check for unmapped < size would move into unmap_end(). Will