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[34.83.136.168]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-847f6dd9237sm6303930b3a.59.2026.07.07.17.23.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Jul 2026 17:23:58 -0700 (PDT) Date: Wed, 8 Jul 2026 00:23:55 +0000 From: Samiullah Khawaja To: Mike Rapoport Cc: Pranjal Shrivastava , Pasha Tatashin , Pratyush Yadav , Alexander Graf , David Matlack , kexec@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 4/4] kho: Introduce kho_split_preserved_pages() helper Message-ID: References: <20260703020832.1731864-1-praan@google.com> <20260703020832.1731864-5-praan@google.com> <178341290877.3292146.993563652569119942.b4-review@b4> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <178341290877.3292146.993563652569119942.b4-review@b4> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260707_172401_831063_B814BD66 X-CRM114-Status: GOOD ( 13.60 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org On Tue, Jul 07, 2026 at 11:28:28AM +0300, Mike Rapoport wrote: >> A driver may need to split a high-order allocation that has already >> been preserved. If the pages are split using split_page() manually, > >Why? >Are there particular examples? > >> the refcounts would change but KHO won't record the change in the >> preserved page-type, resulting in a metadata mismatch during >> restoration in the new kernel. >> >> Introduce kho_split_preserved_pages() to handle splitting of preserved >> pages. The helper follows an unpreserve -> split -> re-preserve sequence, >> while ensuring that the KHO radix tree is updated with the correct >> KHO_PAGE_SPLIT type bits. >> >> The helper returns 0 on success, or a negative error code if the >> re-preservation fails. Callers must ensure the provided order matches >> the original allocation and that the operation is serialized against >> other preservation API calls. > >Let's put this on hold until there are actual users. +1 I think we discussed in this in one of the hypervisor liveudpate meeting sessions and it was concluded that the split of preseved pages is not needed. > >-- >Sincerely yours, >Mike. >