Received-SPF: pass (google.com: domain of linux-kernel+bounces-179160-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.48.161 as permitted sender) client-ip=147.75.48.161;
Date: Tue, 14 May 2024 22:49:44 +0200
From: Oscar Salvador <osalvador@suse.de>
To: =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= <bjorn@kernel.org>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	David Hildenbrand <david@redhat.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	linux-riscv@lists.infradead.org,
	=?iso-8859-1?Q?Bj=F6rn_T=F6pel?= <bjorn@rivosinc.com>,
	Andrew Bresticker <abrestic@rivosinc.com>,
	Chethan Seshadri <Chethan.Seshadri@catalinasystems.io>,
	Lorenzo Stoakes <lstoakes@gmail.com>,
	Santosh Mamila <santosh.mamila@catalinasystems.io>,
	Sivakumar Munnangi <siva.munnangi@catalinasystems.io>,
	Sunil V L <sunilvl@ventanamicro.com>, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, virtualization@lists.linux-foundation.org
Subject: Re: [PATCH v2 4/8] riscv: mm: Add memory hotplugging support
Message-ID: <ZkPOaAUZrRWRGke0@localhost.localdomain>
References: <20240514140446.538622-1-bjorn@kernel.org>
 <20240514140446.538622-5-bjorn@kernel.org>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20240514140446.538622-5-bjorn@kernel.org>

On Tue, May 14, 2024 at 04:04:42PM +0200, Bj?rn T?pel wrote:
> +static void __meminit free_vmemmap_storage(struct page *page, size_t size,
> +					   struct vmem_altmap *altmap)
> +{
> +	if (altmap)
> +		vmem_altmap_free(altmap, size >> PAGE_SHIFT);
> +	else
> +		free_pages((unsigned long)page_address(page), get_order(size));

David already pointed this out, but can check
arch/x86/mm/init_64.c:free_pagetable().

You will see that we have to do some magic for bootmem memory (DIMMs
which were not hotplugged but already present)

> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> +void __ref vmemmap_free(unsigned long start, unsigned long end, struct vmem_altmap *altmap)
> +{
> +	remove_pgd_mapping(start, end, true, altmap);
> +}
> +#endif /* CONFIG_SPARSEMEM_VMEMMAP */
> +#endif /* CONFIG_MEMORY_HOTPLUG */

I will comment on the patch where you add support for hotplug and the
dependency, but on a track in LSFMM today, we decided that most likely
we will drop memory-hotplug support for !CONFIG_SPARSEMEM_VMEMMAP
environments.
So, since you are adding this plain fresh, please consider to tight the
hotplug dependency to CONFIG_SPARSEMEM_VMEMMAP.
As a bonus, you will only have to maintain one flavour of functions.


-- 
Oscar Salvador
SUSE Labs