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b=nBLlXIJzdfgq1Dnn+DyMW+MquYwEJofXKI4D2doa79u6kD0MRYJb6l1wAT6BKDb4s XkpwiiFiqbKfGMVfvT8HoBcPne3ZtUfGcQMHgNMjZOdEox5BZGDjUu6NLw/q73HkDN KIcn8FPQaV0jrEW+3EZd6+NHCZ/C7oJrgbMiniwrgh/D+B2YyTkzf9rkuWnnrw5zNV oExQ+29v47kcWhJnY1/nU0WUAgIKX8vBNRqiM1O/2Zuj8ibSW0Yxgw1vrdCldKRTfW 8MoQF0Q/RYYNs23aF991zxpDZQRIciTAlIu5nMZBXmqE3+uw9puCKIyTokUzycVfJk GwSD2QuKfRARA== Date: Tue, 16 Dec 2025 17:19:26 +0200 From: Mike Rapoport To: Pasha Tatashin Cc: Evangelos Petrongonas , Pratyush Yadav , Alexander Graf , Andrew Morton , Jason Miu , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org, nh-open-source@amazon.com Subject: Re: [PATCH] kho: add support for deferred struct page init Message-ID: References: <20251216084913.86342-1-epetron@amazon.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 27F47180022 X-Stat-Signature: hkbbxz3i1ogme9586bomf3ug3w18pf7m X-Rspam-User: X-HE-Tag: 1765898375-593842 X-HE-Meta: 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 zjpIv1/2 IVbrXLh9ugXm5fj7qbr+op++MY0Y22QAquGycje8JfBOZP4mllNcJa5bu6rYFmYwjx7Wvv1iDg75V11Cm7n9llEwJwFv7HRE2Isb+g4Wj9mAXZUA/4N+Z0LnAcWiTL6Egl8Z/tJgJ4zS/IeKIM+r1VZKX9c1yo39PcFvor3rlE+kCPReBqBjnS+G1mT5DtjTI5IOHAoOQXyUQ0OqOvL+glGE/iX25VmdrEpM2hvemfg5sGWCcXOjp5cwC+FwQKzlmZCg7PrZ0T2tqE9S16rH7AiwsjA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Dec 16, 2025 at 10:05:27AM -0500, Pasha Tatashin wrote: > > > +static struct page *__init kho_get_preserved_page(phys_addr_t phys, > > > + unsigned int order) > > > +{ > > > + unsigned long pfn = PHYS_PFN(phys); > > > + int nid = early_pfn_to_nid(pfn); > > > + > > > + for (int i = 0; i < (1 << order); i++) > > > + init_deferred_page(pfn + i, nid); > > > > This will skip pages below node->first_deferred_pfn, we need to use > > __init_page_from_nid() here. > > Mike, but those struct pages should be initialized early anyway. If > they are not yet initialized we have a problem, as they are going to > be re-initialized later. Can say I understand your point. Which pages should be initialized earlt? And which pages will be reinitialized? > > > + > > > + return pfn_to_page(pfn); > > > +} > > > + > > > static void __init deserialize_bitmap(unsigned int order, > > > struct khoser_mem_bitmap_ptr *elm) > > > { > > > @@ -449,7 +466,7 @@ static void __init deserialize_bitmap(unsigned int order, > > > int sz = 1 << (order + PAGE_SHIFT); > > > phys_addr_t phys = > > > elm->phys_start + (bit << (order + PAGE_SHIFT)); > > > - struct page *page = phys_to_page(phys); > > > + struct page *page = kho_get_preserved_page(phys, order); > > > > I think it's better to initialize deferred struct pages later in > > kho_restore_page. deserialize_bitmap() runs before SMP and it already does > > The KHO memory should still be accessible early in boot, right? The memory is accessible. And we anyway should not use struct page for preserved memory before kho_restore_{folio,pages}. > > heavy lifting of memblock_reserve()s. Delaying struct page initialization > > until restore makes it at least run in parallel with other initialization > > tasks. > > > > I started to work on this just before plumbers and I have something > > untested here: > > > > https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git/log/?h=kho/deferred-page/v0.1 > > > > > union kho_page_info info; > > > > > > memblock_reserve(phys, sz); > > > -- -- Sincerely yours, Mike.