From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S971753AbeCSU4W (ORCPT ); Mon, 19 Mar 2018 16:56:22 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:35922 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S968538AbeCSU4N (ORCPT ); Mon, 19 Mar 2018 16:56:13 -0400 Subject: Re: [RFC 02/12] KVM: arm/arm64: Document KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION To: Marc Zyngier , eric.auger.pro@gmail.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, cdall@kernel.org, peter.maydell@linaro.org References: <1521451220-27754-1-git-send-email-eric.auger@redhat.com> <1521451220-27754-3-git-send-email-eric.auger@redhat.com> Cc: andre.przywara@arm.com, drjones@redhat.com, wei@redhat.com From: Auger Eric Message-ID: <93b3cb3b-6ceb-0277-154e-14bfa5b8f0e6@redhat.com> Date: Mon, 19 Mar 2018 21:56:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Marc, On 19/03/18 15:15, Marc Zyngier wrote: > On 19/03/18 09:20, Eric Auger wrote: >> We introduce a new KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION attribute in >> KVM_DEV_ARM_VGIC_GRP_ADDR group. It allows userspace to provide the >> base address and size of a redistributor region >> >> Compared to KVM_VGIC_V3_ADDR_TYPE_REDIST, this new attribute allows >> to declare several separate redistributor regions. >> >> So the whole redist space does not need to be contiguous anymore. >> >> Signed-off-by: Eric Auger >> --- >> Documentation/virtual/kvm/devices/arm-vgic-v3.txt | 12 ++++++++++++ >> 1 file changed, 12 insertions(+) >> >> diff --git a/Documentation/virtual/kvm/devices/arm-vgic-v3.txt b/Documentation/virtual/kvm/devices/arm-vgic-v3.txt >> index 9293b45..2c0bedf 100644 >> --- a/Documentation/virtual/kvm/devices/arm-vgic-v3.txt >> +++ b/Documentation/virtual/kvm/devices/arm-vgic-v3.txt >> @@ -27,6 +27,18 @@ Groups: >> VCPU and all of the redistributor pages are contiguous. >> Only valid for KVM_DEV_TYPE_ARM_VGIC_V3. >> This address needs to be 64K aligned. >> + >> + KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION (rw, 64-bit) >> + The attr field of kvm_device_attr encodes 3 values: >> + bits: | 63 .... 52 | 51 .... 12 |11 - 0 >> + values: | pfns | base | index >> + - index encodes the unique redistibutor region index >> + - base field encodes bits [51:12] the guest physical base address >> + of the first redistributor in the region. There are two 64K pages >> + for each VCPU and all of the redistributor pages are contiguous >> + within the redistributor region. > > Why does base have to include bits [15:12] of the IPA? If it is 64kB > aligned (as it should), these bits are guaranteed to be 0. This also > avoid having to return -EINVAL in case of alignment problems. Agreed. I hesitated but saw addresses were generally described with bits[51:12] in regs such as PROPBASER/PENDBASER and I did not really need the spare bits. > >> + - pfns encodes the size of the region in 64kB pages. >> + Only valid for KVM_DEV_TYPE_ARM_VGIC_V3. > > "pfns" a bit of an odd name, and is a bit unnatural. Why don't we > instead encode the number of redistributors? You've already imposed that > a redistributor has 2 64kB pages, I copied the description in KVM_VGIC_V3_ADDR_TYPE_REDIST ;-) I knew that for GICv4 the number of 64kB pages per redist is different so I thought it was more generic. But I don't have a strong opinion. so let's take advantage of this by > saving yet another bit. > > You could dedicate a couple of these bits as a selector for the ITS > version (v3, v4 or whatever comes after that, if ever...). Just make 0 > the only valid version for the time being. OK Thanks Eric > >> Errors: >> -E2BIG: Address outside of addressable IPA range >> -EINVAL: Incorrectly aligned address >> > > Thanks, > > M. >