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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0605EC433FE for ; Wed, 13 Apr 2022 17:02:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237170AbiDMREh (ORCPT ); Wed, 13 Apr 2022 13:04:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44066 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237167AbiDMREb (ORCPT ); Wed, 13 Apr 2022 13:04:31 -0400 Received: from mail-yb1-xb2e.google.com (mail-yb1-xb2e.google.com [IPv6:2607:f8b0:4864:20::b2e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C41E1674FA for ; Wed, 13 Apr 2022 10:02:08 -0700 (PDT) Received: by mail-yb1-xb2e.google.com with SMTP id p65so4856688ybp.9 for ; Wed, 13 Apr 2022 10:02:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Yd7U9Ti5RDg8NJvME8HI4I8ItMkX9qmr1z2pf1IvYK8=; b=ewxTAo1Qxsd5Ttb0O86NkxjzsCqY01zIpBDm2cwF6BqdFEGon1NsnDPdf682lfbOa9 Shw2OpMrmSKooJl5WijgnYp33iEwsr20SAiQIrfsZjy0wJsgzKLugwH65+GOrV+knXDI YT2tG5uoU9WZUy5YcBjkbcLtJYnXmvsIyf9yF5A7Td9FOLGNGy7G2ZFUvAqilgOBVGmE A7uVZqdOms/O/YK9ifqhJ9rCAAOsIuIQy54vWIG9TFj24ufGOhIe7QyWiOB9vLocsjUo FqxxsaFY6BuZ3B43l/MjCcOMumvMep4s/a6U2Mn/fp3OhkrkefL71H2LuR0a4ANnGF3D GnPA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Yd7U9Ti5RDg8NJvME8HI4I8ItMkX9qmr1z2pf1IvYK8=; b=dOyzftz71ccpWJ752+qPi+7Qaz+B47Oaza6CRGfe4FPMJoVKT37EJJIGF90k/VK4FS W5yoB8r1Vx4mOp5rTu2jKevNI7zlllmJW7DLdgaVzC0oVnrYWl58Kb6BW9LL9WQR5Smq UrPzSuSYS+g6NJQfiqIVx4k+28RCqvUeIN40mBxxdksEv8GNBX3fgac+UySVVrXKWE9z PYHTH37gPyvUJb3gsSARxzwNIo67FXcb31RH3cDYiCp+V1qT5utTnaHc7PPdDGsIAoLX 2qrWocfWqwQuekPenwQ6292qupJcF8tj0HaZwsR8z4bEmVTZhRU1pxYkCJIWqzpI2bbf r2dQ== X-Gm-Message-State: AOAM533RgvRFjze4y+Dpw8aTJoFeAOX1BzOaRQssI5A3G5H0xdPJ9KkA 5T5FudWHRzFSzkiLJQQmPsnHEox4H9rXypEEos1Y9w== X-Google-Smtp-Source: ABdhPJxdvNBdxrvRM8ACW9KEOZDUovcWoMkKQluaavSot9hEcA4WNXQ4PgMeFjkiHodhkVrU2iGiruZZGD+RbyPxoCE= X-Received: by 2002:a25:b9c8:0:b0:633:7725:779 with SMTP id y8-20020a25b9c8000000b0063377250779mr29609038ybj.280.1649869327532; Wed, 13 Apr 2022 10:02:07 -0700 (PDT) MIME-Version: 1.0 References: <20220407011605.1966778-1-rananta@google.com> <20220407011605.1966778-7-rananta@google.com> <5dac0a4e-735f-40e3-5073-b548a2ba9855@redhat.com> In-Reply-To: <5dac0a4e-735f-40e3-5073-b548a2ba9855@redhat.com> From: Raghavendra Rao Ananta Date: Wed, 13 Apr 2022 10:01:56 -0700 Message-ID: Subject: Re: [PATCH v5 06/10] Docs: KVM: Add doc for the bitmap firmware registers To: Gavin Shan Cc: Marc Zyngier , Andrew Jones , James Morse , Alexandru Elisei , Suzuki K Poulose , kvm@vger.kernel.org, Catalin Marinas , Peter Shier , linux-kernel@vger.kernel.org, Paolo Bonzini , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Apr 12, 2022 at 11:40 PM Gavin Shan wrote: > > Hi Raghavendra, > > On 4/7/22 9:16 AM, Raghavendra Rao Ananta wrote: > > Add the documentation for the bitmap firmware registers in > > hypercalls.rst and api.rst. This includes the details for > > KVM_REG_ARM_STD_BMAP, KVM_REG_ARM_STD_HYP_BMAP, and > > KVM_REG_ARM_VENDOR_HYP_BMAP registers. > > > > Since the document is growing to carry other hypercall related > > information, make necessary adjustments to present the document > > in a generic sense, rather than being PSCI focused. > > > > Signed-off-by: Raghavendra Rao Ananta > > --- > > Documentation/virt/kvm/api.rst | 17 ++++ > > Documentation/virt/kvm/arm/hypercalls.rst | 95 ++++++++++++++++++----- > > 2 files changed, 94 insertions(+), 18 deletions(-) > > > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > > index d13fa6600467..e0107b157965 100644 > > --- a/Documentation/virt/kvm/api.rst > > +++ b/Documentation/virt/kvm/api.rst > > @@ -2542,6 +2542,23 @@ arm64 firmware pseudo-registers have the following bit pattern:: > > > > 0x6030 0000 0014 > > > > +arm64 bitmap feature firmware pseudo-registers have the following bit pattern:: > > + > > + 0x6030 0000 0016 > > + > > +The bitmap feature firmware registers exposes the hypercall services that are > > +available for userspace to configure. The set bits corresponds to the services > > +that are available for the guests to access. By default, KVM sets all the > > +supported bits during VM initialization. The userspace can discover the > > +available services via KVM_GET_ONE_REG, and write-back the bitmap corresponding > > +to the features that it wishes guests to see via KVM_SET_ONE_REG. > > + > > +Note: These registers are immutable once any of the vCPUs of the VM has run at > > +least once. A KVM_SET_ONE_REG in such a scenario will return a -EBUSY to userspace. > > +If there's no change in the value that's being written, 0 (success) is returned. > > + > > +(See Documentation/virt/kvm/arm/hypercalls.rst for more details.) > > + > > arm64 SVE registers have the following bit patterns:: > > > > 0x6080 0000 0015 00 Zn bits[2048*slice + 2047 : 2048*slice] > > diff --git a/Documentation/virt/kvm/arm/hypercalls.rst b/Documentation/virt/kvm/arm/hypercalls.rst > > index d52c2e83b5b8..ccda9fc2d253 100644 > > --- a/Documentation/virt/kvm/arm/hypercalls.rst > > +++ b/Documentation/virt/kvm/arm/hypercalls.rst > > @@ -1,32 +1,32 @@ > > .. SPDX-License-Identifier: GPL-2.0 > > > > -========================================= > > -Power State Coordination Interface (PSCI) > > -========================================= > > +======================= > > +ARM Hypercall Interface > > +======================= > > > > -KVM implements the PSCI (Power State Coordination Interface) > > -specification in order to provide services such as CPU on/off, reset > > -and power-off to the guest. > > +KVM handles the hypercall services as requested by the guests. New hypercall > > +services are regularly made available by the ARM specification or by KVM (as > > +vendor services) if they make sense from a virtualization point of view. > > > > -The PSCI specification is regularly updated to provide new features, > > -and KVM implements these updates if they make sense from a virtualization > > -point of view. > > - > > -This means that a guest booted on two different versions of KVM can > > -observe two different "firmware" revisions. This could cause issues if > > -a given guest is tied to a particular PSCI revision (unlikely), or if > > -a migration causes a different PSCI version to be exposed out of the > > -blue to an unsuspecting guest. > > +This means that a guest booted on two different versions of KVM can observe > > +two different "firmware" revisions. This could cause issues if a given guest > > +is tied to a particular version of a hypercall service, or if a migration > > +causes a different version to be exposed out of the blue to an unsuspecting > > +guest. > > > > In order to remedy this situation, KVM exposes a set of "firmware > > pseudo-registers" that can be manipulated using the GET/SET_ONE_REG > > interface. These registers can be saved/restored by userspace, and set > > -to a convenient value if required. > > +to a convenient value as required. > > > > -The following register is defined: > > +The following registers are defined: > > > > * KVM_REG_ARM_PSCI_VERSION: > > > > + KVM implements the PSCI (Power State Coordination Interface) > > + specification in order to provide services such as CPU on/off, reset > > + and power-off to the guest. > > + > > - Only valid if the vcpu has the KVM_ARM_VCPU_PSCI_0_2 feature set > > (and thus has already been initialized) > > - Returns the current PSCI version on GET_ONE_REG (defaulting to the > > @@ -74,4 +74,63 @@ The following register is defined: > > KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED: > > The workaround is always active on this vCPU or it is not needed. > > > > -.. [1] https://developer.arm.com/-/media/developer/pdf/ARM_DEN_0070A_Firmware_interfaces_for_mitigating_CVE-2017-5715.pdf > > + > > +Bitmap Feature Firmware Registers > > +--------------------------------- > > + > > +Contrary to the above registers, the following registers exposes the hypercall > > +services in the form of a feature-bitmap to the userspace. This bitmap is > > +translated to the services that are available to the guest. There is a register > > +defined per service call owner and can be accessed via GET/SET_ONE_REG interface. > > + > > +By default, these registers are set with the upper limit of the features that > > +are supported. This way userspace can discover all the electable hypercall services > > +via GET_ONE_REG. The user-space can write-back the desired bitmap back via > > +SET_ONE_REG. The features for the registers that are untouched, probably because > > +userspace isn't aware of them, will be exposed as is to the guest. > > + > > +Note that KVM would't allow the userspace to configure the registers anymore once > > +any of the vCPUs has run at least once. Instead, it will return a -EBUSY. However, > > +if there's no change in the incoming value, it simply returns a success. > > + > > It would be better to replace "a success" with "zero", to be consistent > with "-EBUSY". The suggestion may be invalid if the code needs changes > based on Marc's suggestions. > Yes, I agree. Mentioning 'zero' makes more sense. However, I would be scraping off this logic and return -EBUSY for all the writes after the VM has started. > > +The psuedo-firmware bitmap register are as follows: > > + > > +* KVM_REG_ARM_STD_BMAP: > > + Controls the bitmap of the ARM Standard Secure Service Calls. > > + > > + The following bits are accepted: > > + > > + Bit-0: KVM_REG_ARM_STD_BIT_TRNG_V1_0: > > + The bit represents the services offered under v1.0 of ARM True Random > > + Number Generator (TRNG) specification, ARM DEN0098. > > + > > +* KVM_REG_ARM_STD_HYP_BMAP: > > + Controls the bitmap of the ARM Standard Hypervisor Service Calls. > > + > > + The following bits are accepted: > > + > > + Bit-0: KVM_REG_ARM_STD_HYP_BIT_PV_TIME: > > + The bit represents the Paravirtualized Time service as represented by > > + ARM DEN0057A. > > + > > +* KVM_REG_ARM_VENDOR_HYP_BMAP: > > + Controls the bitmap of the Vendor specific Hypervisor Service Calls. > > + > > + The following bits are accepted: > > + > > + Bit-0: KVM_REG_ARM_VENDOR_HYP_BIT_FUNC_FEAT > > + The bit represents the ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID > > + function-id > > + > > + Bit-1: KVM_REG_ARM_VENDOR_HYP_BIT_PTP: > > + The bit represents the Precision Time Protocol KVM service. > > + > > +Errors: > > + > > + ======= ============================================================= > > + -ENOENT Unknown register accessed. > > + -EBUSY Attempt a 'write' to the register after the VM has started. > > + -EINVAL Invalid bitmap written to the register. > > + ======= ============================================================= > > + > > +.. [1] https://developer.arm.com/-/media/developer/pdf/ARM_DEN_0070A_Firmware_interfaces_for_mitigating_CVE-2017-5715.pdf > > \ No newline at end of file > > > > Thanks, > Gavin > Regards, Raghavendra