linux-kernel - RE: [PATCH v4 1/8] mm: Add a ptdesc flag to mark kernel page tables

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Message-ID: <BL1PR11MB5271EBC02D76FCC56F5B3EE68C08A@BL1PR11MB5271.namprd11.prod.outlook.com>
Date: Fri, 12 Sep 2025 07:58:28 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Lu Baolu <baolu.lu@...ux.intel.com>, Joerg Roedel <joro@...tes.org>, "Will
 Deacon" <will@...nel.org>, Robin Murphy <robin.murphy@....com>, "Jason
 Gunthorpe" <jgg@...dia.com>, Jann Horn <jannh@...gle.com>, Vasant Hegde
	<vasant.hegde@....com>, "Hansen, Dave" <dave.hansen@...el.com>, "Alistair
 Popple" <apopple@...dia.com>, Peter Zijlstra <peterz@...radead.org>,
	Uladzislau Rezki <urezki@...il.com>, Jean-Philippe Brucker
	<jean-philippe@...aro.org>, Andy Lutomirski <luto@...nel.org>, "Lai, Yi1"
	<yi1.lai@...el.com>
CC: "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>, "security@...nel.org"
	<security@...nel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, Dave Hansen <dave.hansen@...ux.intel.com>
Subject: RE: [PATCH v4 1/8] mm: Add a ptdesc flag to mark kernel page tables

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Friday, September 5, 2025 1:51 PM
> 
> +/**
> + * ptdesc_clear_kernel - Mark a ptdesc as no longer used to map the kernel
> + * @ptdesc: The ptdesc to be unmarked
> + *
> + * Use when the ptdesc is no longer used to map the kernel and no longer
> + * needs special handling.
> + */
> +static inline void ptdesc_clear_kernel(struct ptdesc *ptdesc)
> +{
> +	struct folio *folio = ptdesc_folio(ptdesc);
> +
> +	/*
> +	 * Note: the 'PG_referenced' bit does not strictly need to be
> +	 * cleared before freeing the page. But this is nice for
> +	 * symmetry.
> +	 */
> +	folio_clear_referenced(folio);

the comment belongs to the caller?

Reviewed-by: Kevin Tian <kevin.tian@...el.com>