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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 7D0ECC3A59E for ; Wed, 21 Aug 2019 15:37:20 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 3D4ED233A2 for ; Wed, 21 Aug 2019 15:37:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3D4ED233A2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id DE9784A5B6; Wed, 21 Aug 2019 11:37:19 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id kac5eJL2ZVky; Wed, 21 Aug 2019 11:37:18 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 95CF84A5D4; Wed, 21 Aug 2019 11:37:18 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 7C3EA4A59A for ; Wed, 21 Aug 2019 11:37:17 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id X5BPBxBsQJR5 for ; Wed, 21 Aug 2019 11:37:16 -0400 (EDT) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by mm01.cs.columbia.edu (Postfix) with ESMTP id E31EE4A574 for ; Wed, 21 Aug 2019 11:37:15 -0400 (EDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9B225360; Wed, 21 Aug 2019 08:37:15 -0700 (PDT) Received: from e112269-lin.arm.com (e112269-lin.cambridge.arm.com [10.1.196.133]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 995FD3F718; Wed, 21 Aug 2019 08:37:13 -0700 (PDT) From: Steven Price To: Marc Zyngier , Will Deacon , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu Subject: [PATCH v3 01/10] KVM: arm64: Document PV-time interface Date: Wed, 21 Aug 2019 16:36:47 +0100 Message-Id: <20190821153656.33429-2-steven.price@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190821153656.33429-1-steven.price@arm.com> References: <20190821153656.33429-1-steven.price@arm.com> MIME-Version: 1.0 Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Catalin Marinas , linux-doc@vger.kernel.org, Russell King , Steven Price , Paolo Bonzini X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu 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 | 100 ++++++++++++++++++++++++++ 1 file changed, 100 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..1ceb118694e7 --- /dev/null +++ b/Documentation/virt/kvm/arm/pvtime.txt @@ -0,0 +1,100 @@ +Paravirtualized time support for arm64 +====================================== + +Arm specification DEN0057/A defined a standard for paravirtualised time +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 +PV_TIME_ST 0xC5000022 + +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) : Either PV_TIME_LPT or PV_TIME_ST + Return value: (int32) : NOT_SUPPORTED (-1) or SUCCESS (0) if the relevant + PV-time feature is supported by the hypervisor. + +PV_TIME_ST + Function ID: (uint32) : 0xC5000022 + Return value: (int64) : IPA of the stolen time data structure for this + (V)CPU. 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 + 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. + +User space interface +==================== + +User space can request that KVM provide the paravirtualized time interface to +a guest by creating a KVM_DEV_TYPE_ARM_PV_TIME device, for example: + + struct kvm_create_device pvtime_device = { + .type = KVM_DEV_TYPE_ARM_PV_TIME, + .attr = 0, + .flags = 0, + }; + + pvtime_fd = ioctl(vm_fd, KVM_CREATE_DEVICE, &pvtime_device); + +Creation of the device should be done after creating the vCPUs of the virtual +machine. + +The IPA of the structures must be given to KVM. This is the base address +of an array of stolen time structures (one for each VCPU). The base address +must be page aligned. The size must be at least 64 * number of VCPUs and be a +multiple of PAGE_SIZE. + +The memory for these structures should be added to the guest in the usual +manner (e.g. using KVM_SET_USER_MEMORY_REGION). + +For example: + + struct kvm_dev_arm_st_region region = { + .gpa = , + .size = + }; + + struct kvm_device_attr st_base = { + .group = KVM_DEV_ARM_PV_TIME_PADDR, + .attr = KVM_DEV_ARM_PV_TIME_ST, + .addr = (u64)®ion + }; + + ioctl(pvtime_fd, KVM_SET_DEVICE_ATTR, &st_base); -- 2.20.1 _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm