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[34.76.60.220]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-496b4ee1d31sm1129795e9.5.2026.07.24.10.49.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Jul 2026 10:49:25 -0700 (PDT) Date: Fri, 24 Jul 2026 17:49:21 +0000 From: Mostafa Saleh To: Jason Gunthorpe Cc: iommu@lists.linux.dev, "Joerg Roedel (AMD)" , Jean-Philippe Brucker , linux-arm-kernel@lists.infradead.org, Robin Murphy , Will Deacon , David Matlack , Pasha Tatashin , patches@lists.linux.dev, Pranjal Shrivastava , Samiullah Khawaja Subject: Re: [PATCH 1/7] iommupt: Remove the sanity check for pt_num_items_lg2() at the top level Message-ID: References: <0-v1-807e2d1a5efb+e1-iommupt_armv8_jgg@nvidia.com> <1-v1-807e2d1a5efb+e1-iommupt_armv8_jgg@nvidia.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1-v1-807e2d1a5efb+e1-iommupt_armv8_jgg@nvidia.com> On Mon, Jul 06, 2026 at 01:29:07PM -0300, Jason Gunthorpe wrote: > This was ill conceived, the existing formats work OK because they > happen to support pt_num_items_lg2() at the top level. However the > documentation is clear that is not permitted because ARMv8 has > concatenated top levels and we do not want to calculate an exact > pt_num_items_lg2() for the top level special case. > > The logic to compute the number of items of the top level is shown in > pt_top_memsize_lg2() which is: > > num_items_lg2 = common->max_vasz_lg2 - pt_table_item_lg2sz(&pts); > > Which is pointless to try and sanity check. > > Signed-off-by: Jason Gunthorpe Reviewed-by: Mostafa Saleh Thanks, Mostafa > --- > drivers/iommu/generic_pt/iommu_pt.h | 14 -------------- > 1 file changed, 14 deletions(-) > > diff --git a/drivers/iommu/generic_pt/iommu_pt.h b/drivers/iommu/generic_pt/iommu_pt.h > index c2752151c80af1..f1320c7e88dbbb 100644 > --- a/drivers/iommu/generic_pt/iommu_pt.h > +++ b/drivers/iommu/generic_pt/iommu_pt.h > @@ -1207,20 +1207,6 @@ static int pt_init_common(struct pt_common *common) > PT_FORCE_ENABLED_FEATURES)) > return -EOPNOTSUPP; > > - /* > - * Check if the top level of the page table is too small to hold the > - * specified maxvasz. > - */ > - if (!pt_feature(common, PT_FEAT_DYNAMIC_TOP) && > - top_range.top_level != PT_MAX_TOP_LEVEL) { > - struct pt_state pts = { .range = &top_range, > - .level = top_range.top_level }; > - > - if (common->max_vasz_lg2 > > - pt_num_items_lg2(&pts) + pt_table_item_lg2sz(&pts)) > - return -EOPNOTSUPP; > - } > - > if (common->max_oasz_lg2 == 0) > common->max_oasz_lg2 = pt_max_oa_lg2(common); > else > -- > 2.43.0 >