From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D1850C3279B for ; Wed, 4 Jul 2018 22:03:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7309D216F9 for ; Wed, 4 Jul 2018 22:03:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7309D216F9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752976AbeGDWCx (ORCPT ); Wed, 4 Jul 2018 18:02:53 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:43086 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752844AbeGDWCv (ORCPT ); Wed, 4 Jul 2018 18:02:51 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DC39418A; Wed, 4 Jul 2018 15:02:50 -0700 (PDT) Received: from [10.37.10.44] (unknown [10.37.10.44]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5BFB03F5A0; Wed, 4 Jul 2018 15:02:47 -0700 (PDT) Subject: Re: [PATCH v3 15/20] kvm: arm/arm64: Allow tuning the physical address size for VM To: Will Deacon Cc: 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, julien.grall@arm.com, catalin.marinas@arm.com, punit.agrawal@arm.com, qemu-devel@nongnu.org, Peter Maydel , Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= References: <1530270944-11351-1-git-send-email-suzuki.poulose@arm.com> <1530270944-11351-16-git-send-email-suzuki.poulose@arm.com> <20180704155104.GN4828@arm.com> From: Suzuki K Poulose Message-ID: <12d1832a-1a13-7dd4-662b-addf58400789@arm.com> Date: Wed, 4 Jul 2018 23:03:10 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180704155104.GN4828@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/04/2018 04:51 PM, Will Deacon wrote: > Hi Suzuki, > > On Fri, Jun 29, 2018 at 12:15:35PM +0100, Suzuki K Poulose wrote: >> Allow specifying the physical address size for a new VM via >> the kvm_type argument for KVM_CREATE_VM ioctl. This allows >> us to finalise the stage2 page table format as early as possible >> and hence perform the right checks on the memory slots without >> complication. The size is encoded as Log2(PA_Size) in the bits[7:0] >> of the type field and can encode more information in the future if >> required. The IPA size is still capped at 40bits. >> >> Cc: Marc Zyngier >> Cc: Christoffer Dall >> Cc: Peter Maydel >> Cc: Paolo Bonzini >> Cc: Radim Krčmář >> Signed-off-by: Suzuki K Poulose >> --- >> arch/arm/include/asm/kvm_mmu.h | 2 ++ >> arch/arm64/include/asm/kvm_arm.h | 10 +++------- >> arch/arm64/include/asm/kvm_mmu.h | 2 ++ >> include/uapi/linux/kvm.h | 10 ++++++++++ >> virt/kvm/arm/arm.c | 24 ++++++++++++++++++++++-- >> 5 files changed, 39 insertions(+), 9 deletions(-) > > [...] > >> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h >> index 4df9bb6..fa4cab0 100644 >> --- a/include/uapi/linux/kvm.h >> +++ b/include/uapi/linux/kvm.h >> @@ -751,6 +751,16 @@ struct kvm_ppc_resize_hpt { >> #define KVM_S390_SIE_PAGE_OFFSET 1 >> >> /* >> + * On arm/arm64, machine type can be used to request the physical >> + * address size for the VM. Bits [7-0] have been reserved for the >> + * PA size shift (i.e, log2(PA_Size)). For backward compatibility, >> + * value 0 implies the default IPA size, which is 40bits. >> + */ >> +#define KVM_VM_TYPE_ARM_PHYS_SHIFT_MASK 0xff >> +#define KVM_VM_TYPE_ARM_PHYS_SHIFT(x) \ >> + ((x) & KVM_VM_TYPE_ARM_PHYS_SHIFT_MASK) > > This seems like you're allocating quite a lot of bits in a non-extensible > interface to a fairly esoteric parameter. Would it be better to add another > ioctl, or condense the number of sizes you support instead? As I explained in the other thread, we need the size as soon as the VM is created. The major challenge is keeping the backward compatibility by mapping 0 to 40bits. I will give it a thought. Suzuki