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b=WO8IcdGXQ0Tc67QzXNWENs/BXaSCO+3Ot1YABbffhiA/Howp0f1asS2WJ2hTHFol6 2+0mylwMssClZNggRszcaeyQA3lzVdacjpZ26hZ444vOwuWIa0gHSefxSNYM2rxkyW G12fyasFzCVdPS0pAW6JmCaLYYbiC2S7KRUcjMdZEapajKk9XBkyznNBsKu5U4AHZD BQ0WxH4g1bB1fOO8CX67HpxY6wzgifK0xiGcHzg5kqfX6b8xI7HsRZONHAv4STd0A2 W6TnzvubponvquD2Ryd/MeCJlamvEFPworipOdoXNEXWFg+pXCw8xM2oGaQ/NBkdt6 gfLooe6TTju1w== From: Pratyush Yadav To: Pasha Tatashin Cc: akpm@linux-foundation.org, bhe@redhat.com, rppt@kernel.org, jasonmiu@google.com, arnd@arndb.de, coxu@redhat.com, dave@vasilevsky.ca, ebiggers@google.com, graf@amazon.com, kees@kernel.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org Subject: Re: [PATCH v1 11/13] kho: Allow memory preservation state updates after finalization In-Reply-To: <20251114155358.2884014-12-pasha.tatashin@soleen.com> (Pasha Tatashin's message of "Fri, 14 Nov 2025 10:53:56 -0500") References: <20251114155358.2884014-1-pasha.tatashin@soleen.com> <20251114155358.2884014-12-pasha.tatashin@soleen.com> Date: Fri, 14 Nov 2025 18:33:35 +0100 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: A4251140011 X-Stat-Signature: ss3qs9sy3bh4nngyfeypd7jkxhpnsnuf X-Rspam-User: X-HE-Tag: 1763141619-279558 X-HE-Meta: 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 eMywheMR dmnMMv2YdCpLw22k18cnRJsyw76AzwTfczL0JpOw1tyslViyOvQP1q7ltdElp8PNXa3NoqfT0ac4dgtU5azVgENNR7wYantY7/QoDOYGZd2/UJBkovMTrWv0yngk5z+/DwJSzgdsgHXN22mhaU5aWsKFcSfR3NUhLMHkSC/npYDtGMrdJ+GMfX3KjYUfUKpXUB5aFyCjBdkNt57b5OuCvlJs631zSIrmwhyKktF9RvZVzukY= 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 Fri, Nov 14 2025, Pasha Tatashin wrote: > Currently, kho_preserve_* and kho_unpreserve_* return -EBUSY if > KHO is finalized. This enforces a rigid "freeze" on the KHO memory > state. > > With the introduction of re-entrant finalization, this restriction is > no longer necessary. Users should be allowed to modify the preservation > set (e.g., adding new pages or freeing old ones) even after an initial > finalization. > > The intended workflow for updates is now: > 1. Modify state (preserve/unpreserve). > 2. Call kho_finalize() again to refresh the serialized metadata. > > Remove the kho_out.finalized checks to enable this dynamic behavior. > > Signed-off-by: Pasha Tatashin > --- > kernel/liveupdate/kexec_handover.c | 13 ------------- > 1 file changed, 13 deletions(-) > > diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c > index 27ef20565a5f..87e9b488237d 100644 > --- a/kernel/liveupdate/kexec_handover.c > +++ b/kernel/liveupdate/kexec_handover.c > @@ -183,10 +183,6 @@ static int __kho_preserve_order(struct kho_mem_track *track, unsigned long pfn, > const unsigned long pfn_high = pfn >> order; > > might_sleep(); > - > - if (kho_out.finalized) > - return -EBUSY; > - > physxa = xa_load(&track->orders, order); > if (!physxa) { > int err; > @@ -815,9 +811,6 @@ int kho_unpreserve_folio(struct folio *folio) This can be void now. This would make consumers a bit simpler, since right now, the memfd preservation logic does a WARN_ON() if this function fails. That can be dropped now that the function can never fail. Same for kho_unpreserve_pages() and kho_unpreserve_vmalloc(). > const unsigned int order = folio_order(folio); > struct kho_mem_track *track = &kho_out.track; > > - if (kho_out.finalized) > - return -EBUSY; > - > __kho_unpreserve_order(track, pfn, order); > return 0; > } > @@ -885,9 +878,6 @@ int kho_unpreserve_pages(struct page *page, unsigned int nr_pages) > const unsigned long start_pfn = page_to_pfn(page); > const unsigned long end_pfn = start_pfn + nr_pages; > > - if (kho_out.finalized) > - return -EBUSY; > - > __kho_unpreserve(track, start_pfn, end_pfn); > > return 0; > @@ -1066,9 +1056,6 @@ EXPORT_SYMBOL_GPL(kho_preserve_vmalloc); > */ > int kho_unpreserve_vmalloc(struct kho_vmalloc *preservation) > { > - if (kho_out.finalized) > - return -EBUSY; > - > kho_vmalloc_free_chunks(preservation); > > return 0; -- Regards, Pratyush Yadav