linux-kernel - Re: [PATCH v4 6/8] mm: Introduce deferred freeing for kernel page tables

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Message-ID: <b780f8d9-b306-4061-abc3-b02d24676d63@intel.com>
Date: Fri, 5 Sep 2025 12:26:23 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Jason Gunthorpe <jgg@...dia.com>, Lu Baolu <baolu.lu@...ux.intel.com>
Cc: Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
 Robin Murphy <robin.murphy@....com>, Kevin Tian <kevin.tian@...el.com>,
 Jann Horn <jannh@...gle.com>, Vasant Hegde <vasant.hegde@....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>, Yi Lai <yi1.lai@...el.com>,
 iommu@...ts.linux.dev, security@...nel.org, linux-kernel@...r.kernel.org,
 Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH v4 6/8] mm: Introduce deferred freeing for kernel page
 tables

On 9/5/25 11:43, Jason Gunthorpe wrote:
> On Fri, Sep 05, 2025 at 01:51:01PM +0800, Lu Baolu wrote:
>> +#ifdef CONFIG_ASYNC_PGTABLE_FREE
>> +void pagetable_free_async(struct ptdesc *pt);
>> +#else
>> +static inline void pagetable_free_async(struct ptdesc *pt)
>> +{
>> +	__pagetable_free(pt);
>> +}
>> +#endif
> 
> I'd probably call this function pagetable_free_kernel() ? Weird to
> call it async when it isn't async..
> 
> ptdesc_clear_kernel()?

Fine with me.

>> +	list_for_each_entry_safe(pt, next, &page_list, pt_list) {
>> +		list_del(&pt->pt_list);
> 
> The list_del isn't necessary, it doesn't zero the list, just _safe
> iteration is fine.
Ahh, yes, agreed. The list_head is on the stack and going away. The
global list is now empty after the list splice.