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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 843CCC32792 for ; Thu, 3 Oct 2019 12:19:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5AF0F20862 for ; Thu, 3 Oct 2019 12:19:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729506AbfJCMTO (ORCPT ); Thu, 3 Oct 2019 08:19:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39714 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728095AbfJCMTO (ORCPT ); Thu, 3 Oct 2019 08:19:14 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 334532A09AC; Thu, 3 Oct 2019 12:19:13 +0000 (UTC) Received: from kamzik.brq.redhat.com (unknown [10.43.2.160]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7A6315D6A9; Thu, 3 Oct 2019 12:19:05 +0000 (UTC) Date: Thu, 3 Oct 2019 14:19:03 +0200 From: Andrew Jones To: Steven Price Cc: Marc Zyngier , Will Deacon , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, Catalin Marinas , Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , Russell King , James Morse , Julien Thierry , Suzuki K Pouloze , Mark Rutland , kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 01/10] KVM: arm64: Document PV-time interface Message-ID: <20191003121903.vty3gikjrqxffgch@kamzik.brq.redhat.com> References: <20191002145037.51630-1-steven.price@arm.com> <20191002145037.51630-2-steven.price@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191002145037.51630-2-steven.price@arm.com> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Thu, 03 Oct 2019 12:19:13 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 02, 2019 at 03:50:28PM +0100, Steven Price wrote: > Introduce a paravirtualization interface for KVM/arm64 based on the > "Arm Paravirtualized Time for Arm-Base Systems" specification DEN 0057A. > > This only adds the details about "Stolen Time" as the details of "Live > Physical Time" have not been fully agreed. > > User space can specify a reserved area of memory for the guest and > inform KVM to populate the memory with information on time that the host > kernel has stolen from the guest. > > A hypercall interface is provided for the guest to interrogate the > hypervisor's support for this interface and the location of the shared > memory structures. > > Signed-off-by: Steven Price > --- > Documentation/virt/kvm/arm/pvtime.txt | 65 +++++++++++++++++++++++++ > Documentation/virt/kvm/devices/vcpu.txt | 14 ++++++ > 2 files changed, 79 insertions(+) > create mode 100644 Documentation/virt/kvm/arm/pvtime.txt > > diff --git a/Documentation/virt/kvm/arm/pvtime.txt b/Documentation/virt/kvm/arm/pvtime.txt > new file mode 100644 > index 000000000000..fa15c12eec91 > --- /dev/null > +++ b/Documentation/virt/kvm/arm/pvtime.txt Maybe use .rst instead of .txt? > @@ -0,0 +1,65 @@ > +Paravirtualized time support for arm64 > +====================================== > + > +Arm specification DEN0057/A defined a standard for paravirtualised time s/defined/defines/ ? > +support for AArch64 guests: > + > +https://developer.arm.com/docs/den0057/a > + > +KVM/arm64 implements the stolen time part of this specification by providing > +some hypervisor service calls to support a paravirtualized guest obtaining a > +view of the amount of time stolen from its execution. > + > +Two new SMCCC compatible hypercalls are defined: > + > +PV_FEATURES 0xC5000020 The spec calls this PV_TIME_FEATURES. > +PV_TIME_ST 0xC5000022 This is 0xC5000021 in the spec. > + > +These are only available in the SMC64/HVC64 calling convention as > +paravirtualized time is not available to 32 bit Arm guests. The existence of > +the PV_FEATURES hypercall should be probed using the SMCCC 1.1 ARCH_FEATURES > +mechanism before calling it. > + > +PV_FEATURES > + Function ID: (uint32) : 0xC5000020 > + PV_func_id: (uint32) : The function to query for support. > + Currently only PV_TIME_ST is supported. The spec calls this PV_call_id, but maybe PV_func_id would have been better. > + Return value: (int32) : NOT_SUPPORTED (-1) or SUCCESS (0) if the relevant > + PV-time feature is supported by the hypervisor. This is an int64 in the spec. > + > +PV_TIME_ST > + Function ID: (uint32) : 0xC5000022 > + Return value: (int64) : IPA of the stolen time data structure for this > + VCPU. On failure: > + NOT_SUPPORTED (-1) > + > +The IPA returned by PV_TIME_ST should be mapped by the guest as normal memory > +with inner and outer write back caching attributes, in the inner shareable > +domain. A total of 16 bytes from the IPA returned are guaranteed to be > +meaningfully filled by the hypervisor (see structure below). > + > +PV_TIME_ST returns the structure for the calling VCPU. > + > +Stolen Time > +----------- > + > +The structure pointed to by the PV_TIME_ST hypercall is as follows: > + > + Field | Byte Length | Byte Offset | Description > + ----------- | ----------- | ----------- | -------------------------- > + Revision | 4 | 0 | Must be 0 for version 0.1 The spec version is 1.0 and Table 1 says "For implementations compliant with this revision of the specification...". So I think this description should be "Must be 0 for version 1.0". > + Attributes | 4 | 4 | Must be 0 > + Stolen time | 8 | 8 | Stolen time in unsigned > + | | | nanoseconds indicating how > + | | | much time this VCPU thread > + | | | was involuntarily not > + | | | running on a physical CPU. > + > +The structure will be updated by the hypervisor prior to scheduling a VCPU. It > +will be present within a reserved region of the normal memory given to the > +guest. The guest should not attempt to write into this memory. There is a > +structure per VCPU of the guest. > + > +For the user space interface see Documentation/virt/kvm/devices/vcpu.txt > +section "3. GROUP: KVM_ARM_VCPU_PVTIME_CTRL". > + > diff --git a/Documentation/virt/kvm/devices/vcpu.txt b/Documentation/virt/kvm/devices/vcpu.txt > index 2b5dab16c4f2..6f3bd64a05b0 100644 > --- a/Documentation/virt/kvm/devices/vcpu.txt > +++ b/Documentation/virt/kvm/devices/vcpu.txt > @@ -60,3 +60,17 @@ time to use the number provided for a given timer, overwriting any previously > configured values on other VCPUs. Userspace should configure the interrupt > numbers on at least one VCPU after creating all VCPUs and before running any > VCPUs. > + > +3. GROUP: KVM_ARM_VCPU_PVTIME_CTRL > +Architectures: ARM64 > + > +3.1 ATTRIBUTE: KVM_ARM_VCPU_PVTIME_IPA > +Parameters: 64-bit base address > +Returns: -ENXIO: Stolen time not implemented > + -EEXIST: Base address already set for this VCPU > + -EINVAL: Base address not 64 byte aligned > + > +Specifies the base address of the stolen time structure for this VCPU. The > +base address must be 64 byte aligned and exist within a valid guest memory > +region. See Documentation/virt/kvm/arm/pvtime.txt for more information > +including the layout of the stolen time structure. > -- > 2.20.1 > Thanks, drew