From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933559AbeCSOP4 (ORCPT ); Mon, 19 Mar 2018 10:15:56 -0400 Received: from foss.arm.com ([217.140.101.70]:53088 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754380AbeCSOPy (ORCPT ); Mon, 19 Mar 2018 10:15:54 -0400 Subject: Re: [RFC 02/12] KVM: arm/arm64: Document KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION To: Eric Auger , 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 Cc: andre.przywara@arm.com, drjones@redhat.com, wei@redhat.com References: <1521451220-27754-1-git-send-email-eric.auger@redhat.com> <1521451220-27754-3-git-send-email-eric.auger@redhat.com> From: Marc Zyngier Organization: ARM Ltd Message-ID: Date: Mon, 19 Mar 2018 14:15:51 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <1521451220-27754-3-git-send-email-eric.auger@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > + - 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, 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. > Errors: > -E2BIG: Address outside of addressable IPA range > -EINVAL: Incorrectly aligned address > Thanks, M. -- Jazz is not dead. It just smells funny...