From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 27A351A028E for ; Mon, 8 Feb 2016 17:01:20 +1100 (AEDT) Date: Mon, 8 Feb 2016 17:00:20 +1100 From: Paul Mackerras To: David Gibson Cc: mpe@ellerman.id.au, benh@kernel.crashing.org, linuxppc-dev@lists.ozlabs.org, aik@ozlabs.ru, thuth@redhat.com, lvivier@redhat.com Subject: Re: [RFCv2 8/9] pseries: Advertise HPT resizing support via CAS Message-ID: <20160208060020.GH30807@oak.ozlabs.ibm.com> References: <1454045043-25545-1-git-send-email-david@gibson.dropbear.id.au> <1454045043-25545-9-git-send-email-david@gibson.dropbear.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1454045043-25545-9-git-send-email-david@gibson.dropbear.id.au> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, Jan 29, 2016 at 04:24:02PM +1100, David Gibson wrote: > The hypervisor needs to know a guest is capable of using the HPT resizing > PAPR extension in order to make full advantage of it for memory hotplug. > > If the hypervisor knows the guest is HPT resize aware, it can size the > initial HPT based on the initial guest RAM size, relying on the guest to > resize the HPT when more memory is hot-added. Without this, the hypervisor > must size the HPT for the maximum possible guest RAM, which can lead to > a huge waste of space if the guest never actually expends to that maximum > size. > > This patch advertises the guest's support for HPT resizing via the > ibm,client-architecture-support OF interface. Obviously, the actual > encoding in the CAS vector is tentative until the extension is officially > incorporated into PAPR. For now we use bit 0 of (previously unused) byte 8 > of option vector 5. > > Signed-off-by: David Gibson Reviewed-by: Paul Mackerras