linux-kernel - Re: [PATCH v5 3/8] x86/mm: Use 'ptdesc' when freeing PMD pages

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Message-ID: <e4c0c578-50e9-4e65-8e7f-7a6d995b22e0@intel.com>
Date: Thu, 9 Oct 2025 12:31:28 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: David Hildenbrand <david@...hat.com>, Lu Baolu
 <baolu.lu@...ux.intel.com>, Joerg Roedel <joro@...tes.org>,
 Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
 Kevin Tian <kevin.tian@...el.com>, Jason Gunthorpe <jgg@...dia.com>,
 Jann Horn <jannh@...gle.com>, Vasant Hegde <vasant.hegde@....com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, 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>
Cc: iommu@...ts.linux.dev, security@...nel.org, x86@...nel.org,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH v5 3/8] x86/mm: Use 'ptdesc' when freeing PMD pages

On 10/9/25 12:25, David Hildenbrand wrote:
>>
>> @@ -750,8 +750,8 @@ int pud_free_pmd_page(pud_t *pud, unsigned long addr)
>>         for (i = 0; i < PTRS_PER_PMD; i++) {
>>           if (!pmd_none(pmd_sv[i])) {
>> -            pte = (pte_t *)pmd_page_vaddr(pmd_sv[i]);
>> -            pte_free_kernel(&init_mm, pte);
>> +            pt = page_ptdesc(pmd_page(pmd_sv[i]));
>> +            pagetable_dtor_free(pt);
> 
> There is pmd_ptdesc() which does
> 
>     page_ptdesc(pmd_pgtable_page(pmd));
> 
> It's buried in a
> 
>     #if defined(CONFIG_SPLIT_PMD_PTLOCKS)
> 
> Can't we just make that always available so we can use it here?

Yes, that looks like a good idea. I never noticed pmd_ptdesc() when I
was writing this for sure.