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b=P0fW5fFjAF5qEShD2FDUvhRLrpwuYauXz7mH0/BSGcs1DeAv1GtmOVVG/2URH7Nil Wp7IYW+Wv03cB9LfWZcRjNFYz0kCgtVvJncN3ac2E9G0ZIkIOdvjPHjh3vg52WlgNo 5Wlw/ejL90a14q4Vviu2IAatKuQrY5GO0AR9xa2hVWWg5/UwMnYgO3AgB+jB+lW+Vc CzV6C9D/37DcbFx8Guens1jLZhndt+gROqpJ0cPyfu1x5sKaz92g9XWah1cqwpx6Wx F5ZvDMs8i/Le+rGQB1xi9V8X65teOuzLFUWnMdc/8rWz+9kJ58E5S9pgQZHGzWWwFC EZyVOU+A0eHzg== Message-ID: <5d20f9b8-9085-49df-87df-05f29f1496a1@kernel.org> Date: Sat, 10 Oct 2026 14:27:34 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/4] riscv/mm: fix hotplug page-table destructor handling To: Muchun Song Cc: Muchun Song , akpm@linux-foundation.org, linux-mm@kvack.org, stable@vger.kernel.org, osalvador@suse.de, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, linux-arm-kernel@lists.infradead.org, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, linux-riscv@lists.infradead.org, agordeev@linux.ibm.com, kevin.brodsky@arm.com, bjorn@rivosinc.com, apopple@nvidia.com, linux-kernel@vger.kernel.org References: <20261008073021.2512665-1-songmuchun@bytedance.com> <20261008073021.2512665-3-songmuchun@bytedance.com> <664510b2-3510-499f-aab5-ceddfcc82581@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 699DA180008 X-Rspam-User: X-Stat-Signature: x3x57u4wwputse39daphzu4m6azg46yn X-HE-Tag: 1791638618-299147 X-HE-Meta: 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 zyTqlqZJ m4FKMKScYZja3s3wda7cevDAwYnSjG/L3KESFC0o/O5M2w9hXhnQEzhgTFbgkMrk2zymh90TwFdjalBStXQmC6+Eji37tZk/bKJBljgHaMn08zWy64aORUvrsCRvYULATyylN8yyOq5MAR3qcav4HvgC3UZvl5YMd61ks/H/rFu/W/eKCPzOJYPNuLYLeO1ZoO0TG/nkJcBQcYtTWmx+FI3nkLqQv8witUsm8cLVwiMx9bWqvMAnKGTRr8RawVf4sEA9iW2tUyvOpaaSpcXeSJ8HewxSHiLTkllq4yK0fx6DOEa1zjEnIP/sVcg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 10/10/26 04:58, Muchun Song wrote: > > >> On Oct 10, 2026, at 04:37, David Hildenbrand (Arm) wrote: >> >> On 10/8/26 09:30, Muchun Song wrote: >>> RISC-V uses the same memory-hotplug teardown code for the linear map and >>> vmemmap, although their page-table pages are not always allocated in the >>> same way. Late linear-map allocations run page-table constructors, while >>> vmemmap and early allocations may provide constructor-free pages. >>> >>> The PTE path unconditionally runs the destructor, which is wrong for >>> constructor-free vmemmap tables. The PMD path avoids that problem by >>> using is_vmemmap as a proxy for constructor state, but that assumption >>> will no longer hold once runtime vmemmap allocations use the normal >>> pgalloc helpers. >>> >>> Page-table constructors record their state in PG_table. Centralize >>> page-table freeing and use PageTable() to decide whether the destructor >>> is required. Keep reserved and constructor-free pages on their existing >>> freeing paths. >>> >>> Fixes: c75a74f4ba19 ("riscv: mm: Add memory hotplugging support") >>> Cc: stable@vger.kernel.org >>> Assisted-by: LLM >>> Signed-off-by: Muchun Song >>> --- >>> arch/riscv/mm/init.c | 29 ++++++++++++++--------------- >>> 1 file changed, 14 insertions(+), 15 deletions(-) >>> >>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c >>> index 857f9a55039c..429a0b015ec1 100644 >>> --- a/arch/riscv/mm/init.c >>> +++ b/arch/riscv/mm/init.c >>> @@ -1486,10 +1486,19 @@ struct execmem_info __init *execmem_arch_setup(void) >>> #endif /* CONFIG_EXECMEM */ >>> >>> #ifdef CONFIG_MEMORY_HOTPLUG >>> +static void __meminit free_pagetable(struct page *page) >>> +{ >>> + if (PageReserved(page)) >>> + free_reserved_page(page); >>> + else if (PageTable(page)) >>> + pagetable_dtor_free(page_ptdesc(page)); >>> + else >>> + pagetable_free(page_ptdesc(page)); >> >> Similar thought, can't we detect that in pagetable_free() somehow and avoid >> requiring callers to handle that? > > I think we can, then pagetable_dtor_free() can be removed because pagetable_free > can handle the case of pagetable_dtor_free. That sounds much cleaner :) -- Cheers, David