From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760045AbbIDN6Y (ORCPT ); Fri, 4 Sep 2015 09:58:24 -0400 Received: from foss.arm.com ([217.140.101.70]:43791 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759968AbbIDN6W (ORCPT ); Fri, 4 Sep 2015 09:58:22 -0400 Date: Fri, 4 Sep 2015 14:58:17 +0100 From: Catalin Marinas To: Ard Biesheuvel Cc: Steve Capper , "kvm@vger.kernel.org" , "Suzuki K. Poulose" , Marc Zyngier , Will Deacon , "linux-kernel@vger.kernel.org" , "kvmarm@lists.cs.columbia.edu" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH 12/14] arm64: Check for selected granule support Message-ID: <20150904135817.GE17253@e104818-lin.cambridge.arm.com> References: <1439465645-22584-1-git-send-email-suzuki.poulose@arm.com> <1439465645-22584-13-git-send-email-suzuki.poulose@arm.com> <55CCAD73.7080702@arm.com> <20150813172946.GD4602@e104818-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 02, 2015 at 12:19:07PM +0200, Ard Biesheuvel wrote: > On 2 September 2015 at 11:48, Ard Biesheuvel wrote: > > Couldn't we allocate some flag bits in the Image header to communicate > > the page size to the bootloader? > > Something like this perhaps? > > ------------8<--------------- > diff --git a/Documentation/arm64/booting.txt b/Documentation/arm64/booting.txt > index 7d9d3c2286b2..13a8aaa9a6e9 100644 > --- a/Documentation/arm64/booting.txt > +++ b/Documentation/arm64/booting.txt > @@ -104,7 +104,8 @@ Header notes: > - The flags field (introduced in v3.17) is a little-endian 64-bit field > composed as follows: > Bit 0: Kernel endianness. 1 if BE, 0 if LE. > - Bits 1-63: Reserved. > + Bits 1-2: Kernel page size. 0=unspecified, 1=4K, 2=16K, 3=64K > + Bits 3-63: Reserved. > > - When image_size is zero, a bootloader should attempt to keep as much > memory as possible free for use by the kernel immediately after the > diff --git a/arch/arm64/kernel/image.h b/arch/arm64/kernel/image.h > index 8fae0756e175..5def289bda84 100644 > --- a/arch/arm64/kernel/image.h > +++ b/arch/arm64/kernel/image.h > @@ -47,7 +47,9 @@ > #define __HEAD_FLAG_BE 0 > #endif > > -#define __HEAD_FLAGS (__HEAD_FLAG_BE << 0) > +#define __HEAD_FLAG_PAGE_SIZE ((PAGE_SHIFT - 10) / 2) > + > +#define __HEAD_FLAGS (__HEAD_FLAG_BE << 0) | (__HEAD_FLAG_PAGE_SIZE << 1) I'm fine with this. -- Catalin