From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 AE5DA274666 for ; Sun, 21 Sep 2025 22:26:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758493585; cv=none; b=fo8cqhnUy1ShGYQ+vzHXRr5qbiYkh0wrKyHAUohgoDrksPvZqX15RyYdTJbFoCvd7wv/ofluxyzAoZ4EzOj0DM+77ePGLZ67/kjAMNRlSI2lYJzfdqN+bmbOiX6YKzFCMRKb1ic90tR39bZjf+ChXcjE4yFWwTdGv9yuPhKyDiQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758493585; c=relaxed/simple; bh=XtVBwRWDivem4lFIQmFrqQLUjW9/5+IVgwmLguSshbQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=lxsIKGo9/4uE3PwBvs6F6pVCYwl+k9wDWwNZ/emvYP/k54yQS3InEalXsOizYO84mdGZgvoKeW73Dv+s5ltOoI3N7TY57ZnNTLyNi2sXJiHfbGPqqCJjp3mjlPL2S8mmj/cY2ZZXlB5Kg6lsoi31reOIubpeURI1frOXBZ4rp2I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=eXHuVgdZ; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="eXHuVgdZ" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=0Goc4fu4E5QtA9qLOcM+4h+EpWxYEBSIjsqPof2KABk=; b=eXHuVgdZPnG4LY9fvzsP9Thzot 7SaWdtBpIJZJ+ZMtycjRH8f62jRq439I7bIDyx/lEVq+2Y10XLWKT4YXi7uMdnYZoofhXR7UdOOOB RSmpSUJ7igwnEk+/VRLt6W6jicEw9dEBpykWNOAi5hSq+cGm/noOLpvNUmbGliqToIXvQ5yXENXp2 RhvcPu7pLZ1vqzz82SGYd/zFFjc43f6hYFhbKRjCSKqROT1b0A30axHs3tfmYRwL7WZZCmarTEiKL JkJqPsmNJcpyljqdklBvphzT8J935OBZoPhSuDwqpF7dZ38OGrRXbJC50KHrwCVSBrEm3TWxEt6d5 dCR4URDA==; Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1v0SVR-0000000COjD-2G10; Sun, 21 Sep 2025 22:26:05 +0000 Date: Sun, 21 Sep 2025 23:26:05 +0100 From: Matthew Wilcox To: Jason Gunthorpe Cc: Jason Miu , Alexander Graf , Andrew Morton , Baoquan He , Changyuan Lyu , David Matlack , David Rientjes , Joel Granados , Marcos Paulo de Souza , Mario Limonciello , Mike Rapoport , Pasha Tatashin , Petr Mladek , "Rafael J . Wysocki" , Steven Chen , Yan Zhao , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC v1 0/4] Make KHO Stateless Message-ID: References: <20250917025019.1585041-1-jasonmiu@google.com> <20250917113609.GB1086830@nvidia.com> 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: <20250917113609.GB1086830@nvidia.com> On Wed, Sep 17, 2025 at 08:36:09AM -0300, Jason Gunthorpe wrote: > On Tue, Sep 16, 2025 at 07:50:15PM -0700, Jason Miu wrote: > > This series transitions KHO from an xarray-based metadata tracking > > system with serialization to using page table like data structures > > that can be passed directly to the next kernel. > > > > The key motivations for this change are to: > > - Eliminate the need for data serialization before kexec. > > - Remove the former KHO state machine by deprecating the finalize > > and abort states. > > - Pass preservation metadata more directly to the next kernel via the FDT. > > > > The new approach uses a per-order page table structure (kho_order_table, > > kho_page_table, kho_bitmap_table) to mark preserved pages. The physical > > address of the root `kho_order_table` is passed in the FDT, allowing the > > next kernel to reconstruct the preserved memory map. > > It is not a "page table" structure, it is just a radix tree with bits > as the leaf. Sounds like the IDA data structure. Maybe that API needs to be enhanced for this use case, but surely using the same data structure would be a good thing?