From: Steven Price <steven.price@arm.com>
To: Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Catalin Marinas <catalin.marinas@arm.com>,
linux-doc@vger.kernel.org, Russell King <linux@armlinux.org.uk>,
Steven Price <steven.price@arm.com>,
Paolo Bonzini <pbonzini@redhat.com>
Subject: [PATCH v6 01/10] KVM: arm64: Document PV-time interface
Date: Fri, 11 Oct 2019 13:59:21 +0100 [thread overview]
Message-ID: <20191011125930.40834-2-steven.price@arm.com> (raw)
In-Reply-To: <20191011125930.40834-1-steven.price@arm.com>
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 <steven.price@arm.com>
---
Documentation/virt/kvm/arm/pvtime.rst | 77 +++++++++++++++++++++++++
Documentation/virt/kvm/devices/vcpu.txt | 14 +++++
2 files changed, 91 insertions(+)
create mode 100644 Documentation/virt/kvm/arm/pvtime.rst
diff --git a/Documentation/virt/kvm/arm/pvtime.rst b/Documentation/virt/kvm/arm/pvtime.rst
new file mode 100644
index 000000000000..de949933ec78
--- /dev/null
+++ b/Documentation/virt/kvm/arm/pvtime.rst
@@ -0,0 +1,77 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Paravirtualized time support for arm64
+======================================
+
+Arm specification DEN0057/A defines 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_TIME_FEATURES: 0xC5000020
+* PV_TIME_ST: 0xC5000021
+
+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_TIME_FEATURES
+ ============= ======== ==========
+ Function ID: (uint32) 0xC5000020
+ PV_call_id: (uint32) The function to query for support.
+ Currently only PV_TIME_ST is supported.
+ Return value: (int64) NOT_SUPPORTED (-1) or SUCCESS (0) if the relevant
+ PV-time feature is supported by the hypervisor.
+ ============= ======== ==========
+
+PV_TIME_ST
+ ============= ======== ==========
+ Function ID: (uint32) 0xC5000021
+ 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 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. |
++-------------+-------------+-------------+----------------------------+
+
+All values in the structure are stored little-endian.
+
+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
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next prev parent reply other threads:[~2019-10-11 12:59 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-11 12:59 [PATCH v6 00/10] arm64: Stolen time support Steven Price
2019-10-11 12:59 ` Steven Price [this message]
2019-10-11 12:59 ` [PATCH v6 02/10] KVM: arm/arm64: Factor out hypercall handling from PSCI code Steven Price
2019-10-11 12:59 ` [PATCH v6 03/10] KVM: arm64: Implement PV_TIME_FEATURES call Steven Price
2019-10-11 12:59 ` [PATCH v6 04/10] KVM: Implement kvm_put_guest() Steven Price
2019-10-11 12:59 ` [PATCH v6 05/10] KVM: arm64: Support stolen time reporting via shared structure Steven Price
2019-10-19 11:12 ` Marc Zyngier
2019-10-21 10:21 ` Steven Price
2019-10-21 10:40 ` Marc Zyngier
2019-10-21 11:24 ` Steven Price
2019-10-11 12:59 ` [PATCH v6 06/10] KVM: Allow kvm_device_ops to be const Steven Price
2019-10-11 12:59 ` [PATCH v6 07/10] KVM: arm64: Provide VCPU attributes for stolen time Steven Price
2019-10-19 11:28 ` Marc Zyngier
2019-10-21 11:00 ` Steven Price
2019-10-11 12:59 ` [PATCH v6 08/10] arm/arm64: Provide a wrapper for SMCCC 1.1 calls Steven Price
2019-10-21 11:42 ` Marc Zyngier
2019-10-21 13:43 ` Steven Price
2019-10-21 14:05 ` Marc Zyngier
2019-10-11 12:59 ` [PATCH v6 09/10] arm/arm64: Make use of the SMCCC 1.1 wrapper Steven Price
2019-10-11 12:59 ` [PATCH v6 10/10] arm64: Retrieve stolen time as paravirtualized guest Steven Price
2019-10-19 20:28 ` Marc Zyngier
2019-10-21 5:01 ` Jürgen Groß
2019-10-21 7:55 ` Marc Zyngier
2019-10-21 12:14 ` Steven Price
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