From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60935) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fak4Q-0000D8-0e for qemu-devel@nongnu.org; Wed, 04 Jul 2018 11:51:54 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fak4P-0001Gd-6a for qemu-devel@nongnu.org; Wed, 04 Jul 2018 11:51:54 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:47214 helo=foss.arm.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fak4O-0001GP-Vj for qemu-devel@nongnu.org; Wed, 04 Jul 2018 11:51:53 -0400 Date: Wed, 4 Jul 2018 16:52:31 +0100 From: Will Deacon Message-ID: <20180704155231.GP4828@arm.com> References: <1530270944-11351-1-git-send-email-suzuki.poulose@arm.com> <1530270944-11351-23-git-send-email-suzuki.poulose@arm.com> <20180704140943.GF4828@arm.com> <8c9bb3cd-f673-17f3-656f-66b7e14fc73c@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8c9bb3cd-f673-17f3-656f-66b7e14fc73c@arm.com> Subject: Re: [Qemu-devel] [kvmtool test PATCH 22/24] kvmtool: arm64: Add support for guest physical address size List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Julien Grall Cc: Suzuki K Poulose , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, james.morse@arm.com, marc.zyngier@arm.com, cdall@kernel.org, eric.auger@redhat.com, catalin.marinas@arm.com, punit.agrawal@arm.com, qemu-devel@nongnu.org On Wed, Jul 04, 2018 at 04:00:11PM +0100, Julien Grall wrote: > On 04/07/18 15:09, Will Deacon wrote: > >On Fri, Jun 29, 2018 at 12:15:42PM +0100, Suzuki K Poulose wrote: > >>Add an option to specify the physical address size used by this > >>VM. > >> > >>Signed-off-by: Suzuki K Poulose > >>--- > >> arm/aarch64/include/kvm/kvm-config-arch.h | 5 ++++- > >> arm/include/arm-common/kvm-config-arch.h | 1 + > >> 2 files changed, 5 insertions(+), 1 deletion(-) > >> > >>diff --git a/arm/aarch64/include/kvm/kvm-config-arch.h b/arm/aarch64/include/kvm/kvm-config-arch.h > >>index 04be43d..dabd22c 100644 > >>--- a/arm/aarch64/include/kvm/kvm-config-arch.h > >>+++ b/arm/aarch64/include/kvm/kvm-config-arch.h > >>@@ -8,7 +8,10 @@ > >> "Create PMUv3 device"), \ > >> OPT_U64('\0', "kaslr-seed", &(cfg)->kaslr_seed, \ > >> "Specify random seed for Kernel Address Space " \ > >>- "Layout Randomization (KASLR)"), > >>+ "Layout Randomization (KASLR)"), \ > >>+ OPT_INTEGER('\0', "phys-shift", &(cfg)->phys_shift, \ > >>+ "Specify maximum physical address size (not " \ > >>+ "the amount of memory)"), > > > >Given that this is a shift value, I think the help message could be more > >informative. Something like: > > > > "Specify maximum number of bits in a guest physical address" > > > >I think I'd actually leave out any mention of memory, because this does > >actually have an effect on the amount of addressable memory in a way that I > >don't think we want to describe in half of a usage message line :) > Is there any particular reasons to expose this option to the user? > > I have recently sent a series to allow the user to specify the position > of the RAM [1]. With that series in mind, I think the user would not really > need to specify the maximum physical shift. Instead we could automatically > find it. Marc makes a good point that it doesn't help for MMIO regions, so I'm trying to understand whether we can do something differently there and avoid sacrificing the type parameter. Will