From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 592EC3314D2 for ; Tue, 10 Mar 2026 10:33:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773138825; cv=none; b=e06+GiqzpDb+fppJ/q87S7Jw671OFjyrRorSLep/QZ1JglXbpogT9Zk1nREmAztiyNsimMRXBmj1mjFDzFoT5jD1z2hAd8fLiIkqCfAeI3Kg3tWPb06fp/0TGpwC16fd1vlrh+uRqhXviunIIHpaZ/aBYGsO57PweP8rcW5J8MM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773138825; c=relaxed/simple; bh=ECE4xmh6kRZf/kIT7/6rB3iS7so/etotWxeKzoWbm+g=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=QAzWSVh1p8VLeyq4EX4Zm0UflXETu4Rtiq9Btyg6f0QVYykbA/3rs+mVqWU3q9tMIQ/KZDLlip3or240GbxMkDo4Mgz8C65vQByiqXyudtgSosPR9ofIQlCgA5aRPSqUY60Z6stCTmrzhTMKb90C0OK1hgR5ZXLLVgLk6yZ2ew0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PoBiWwP/; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="PoBiWwP/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 38C35C19423; Tue, 10 Mar 2026 10:33:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773138824; bh=ECE4xmh6kRZf/kIT7/6rB3iS7so/etotWxeKzoWbm+g=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=PoBiWwP/Rm5yU49N/sDms4v+xmjkjdzd1To0opImrEbV59JC3YYemr/v4RJrp3yjP LvvfPpnP8JK+d7w3Qr6jcO+BUL2mv4wTohbNyO07suKvUOJsdxTvjicOstulgBda+b pB4ugJ/JE5RkftJfWPF9X2YMh0W/4atpTARAW/LTXbXjgua/kIMcTc5P/zQcMZrJ3k wbCT2aTHtwB+kOGcsDhmLo+Q25U450SutGLnVZEKekCPRpP8hmtgr1QAPTMdzCm5gO 2c3y+56HcVJNEWpv5peHiGeIRWJVj+7NLfQlO5mOH9dTJuy84IBrizkcRc0fZM/cKs uqnD7h5Spsaug== Date: Tue, 10 Mar 2026 12:33:38 +0200 From: Mike Rapoport To: Pratyush Yadav Cc: Alexander Graf , Pasha Tatashin , Andrew Morton , kexec@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] kho: drop restriction on maximum page order Message-ID: References: <20260309123410.382308-1-pratyush@kernel.org> <20260309123410.382308-2-pratyush@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260309123410.382308-2-pratyush@kernel.org> On Mon, Mar 09, 2026 at 12:34:07PM +0000, Pratyush Yadav wrote: > KHO currently restricts the maximum order of a restored page to the > maximum order supported by the buddy allocator. While this works fine > for much of the data passed across kexec, it is possible to have pages > larger than MAX_PAGE_ORDER. > > For one, it is possible to get a larger order when using > kho_preserve_pages() if the number of pages is large enough, since it > tries to combine multiple aligned 0-order preservations into one higher > order preservation. > > For another, upcoming support for hugepages can have gigantic hugepages > being preserved over KHO. > > There is no real reason for this limit. The KHO preservation machinery > can handle any page order. Remove this artificial restriction on max > page order. > > Signed-off-by: Pratyush Yadav > Signed-off-by: Pratyush Yadav (Google) One SOB should be enough ;-) Reviewed-by: Mike Rapoport (Microsoft) > --- > > Notes: > This patch was first sent with this RFC series [0]. I am sending it > separately since it is an independent patch that is useful even without > hugepage preservation. No changes since the RFC. > > [0] https://lore.kernel.org/linux-mm/20251206230222.853493-1-pratyush@kernel.org/T/#u > > kernel/liveupdate/kexec_handover.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c > index bc9bd18294ee..1038e41ff9f9 100644 > --- a/kernel/liveupdate/kexec_handover.c > +++ b/kernel/liveupdate/kexec_handover.c > @@ -253,7 +253,7 @@ static struct page *kho_restore_page(phys_addr_t phys, bool is_folio) > * check also implicitly makes sure phys is order-aligned since for > * non-order-aligned phys addresses, magic will never be set. > */ > - if (WARN_ON_ONCE(info.magic != KHO_PAGE_MAGIC || info.order > MAX_PAGE_ORDER)) > + if (WARN_ON_ONCE(info.magic != KHO_PAGE_MAGIC)) > return NULL; > nr_pages = (1 << info.order); > > -- > 2.53.0.473.g4a7958ca14-goog > -- Sincerely yours, Mike.