From: Marc Zyngier <maz@kernel.org>
To: "Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
Andrew Jones <drjones@redhat.com>,
kvm@vger.kernel.org, Eric Auger <eric.auger@redhat.com>,
Heinrich Schuchardt <xypron.glpk@gmx.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Christoffer Dall <christoffer.dall@arm.com>,
Steven Price <steven.price@arm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Julien Grall <julien.grall@arm.com>,
Alexander Graf <graf@amazon.com>,
linux-arm-kernel@lists.infradead.org,
Zenghui Yu <yuzenghui@huawei.com>,
James Morse <james.morse@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Will Deacon <will@kernel.org>,
kvmarm@lists.cs.columbia.edu,
Julien Thierry <julien.thierry.kdev@gmail.com>
Subject: [PATCH 03/22] KVM: arm64: Document PV-time interface
Date: Wed, 20 Nov 2019 16:42:17 +0000 [thread overview]
Message-ID: <20191120164236.29359-4-maz@kernel.org> (raw)
In-Reply-To: <20191120164236.29359-1-maz@kernel.org>
From: Steven Price <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>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
Documentation/virt/kvm/arm/pvtime.rst | 80 +++++++++++++++++++++++++
Documentation/virt/kvm/devices/vcpu.txt | 14 +++++
2 files changed, 94 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..2357dd2d8655
--- /dev/null
+++ b/Documentation/virt/kvm/arm/pvtime.rst
@@ -0,0 +1,80 @@
+.. 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.
+
+It is advisable that one or more 64k pages are set aside for the purpose of
+these structures and not used for other purposes, this enables the guest to map
+the region using 64k pages and avoids conflicting attributes with other memory.
+
+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:[~2019-11-20 16:44 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-20 16:42 [GIT PULL] KVM/arm updates for 5.5 Marc Zyngier
2019-11-20 16:42 ` [PATCH 01/22] KVM: arm/arm64: Allow reporting non-ISV data aborts to userspace Marc Zyngier
2019-11-20 16:42 ` [PATCH 02/22] KVM: arm/arm64: Allow user injection of external data aborts Marc Zyngier
2019-11-20 16:42 ` Marc Zyngier [this message]
2019-11-20 16:42 ` [PATCH 04/22] KVM: arm/arm64: Factor out hypercall handling from PSCI code Marc Zyngier
2019-11-20 16:42 ` [PATCH 05/22] KVM: arm64: Implement PV_TIME_FEATURES call Marc Zyngier
2019-11-20 16:42 ` [PATCH 06/22] KVM: Implement kvm_put_guest() Marc Zyngier
2019-11-20 16:42 ` [PATCH 07/22] KVM: arm64: Support stolen time reporting via shared structure Marc Zyngier
2019-11-20 16:42 ` [PATCH 08/22] KVM: Allow kvm_device_ops to be const Marc Zyngier
2019-11-20 16:42 ` [PATCH 09/22] KVM: arm64: Provide VCPU attributes for stolen time Marc Zyngier
2019-11-20 16:42 ` [PATCH 10/22] arm/arm64: Provide a wrapper for SMCCC 1.1 calls Marc Zyngier
2019-11-20 16:42 ` [PATCH 11/22] arm/arm64: Make use of the SMCCC 1.1 wrapper Marc Zyngier
2019-11-20 16:42 ` [PATCH 12/22] arm64: Retrieve stolen time as paravirtualized guest Marc Zyngier
2019-11-20 16:42 ` [PATCH 13/22] KVM: arm64: Select TASK_DELAY_ACCT+TASKSTATS rather than SCHEDSTATS Marc Zyngier
2019-11-20 16:42 ` [PATCH 14/22] KVM: arm/arm64: Show halt poll counters in debugfs Marc Zyngier
2019-11-20 16:42 ` [PATCH 15/22] KVM: arm64: Don't set HCR_EL2.TVM when S2FWB is supported Marc Zyngier
2019-11-20 16:42 ` [PATCH 16/22] KVM: arm64: vgic-v4: Move the GICv4 residency flow to be driven by vcpu_load/put Marc Zyngier
2019-11-20 16:42 ` [PATCH 17/22] KVM: arm/arm64: vgic: Remove the declaration of kvm_send_userspace_msi() Marc Zyngier
2019-11-20 16:42 ` [PATCH 18/22] KVM: arm/arm64: vgic: Fix some comments typo Marc Zyngier
2019-11-20 16:42 ` [PATCH 19/22] KVM: arm/arm64: vgic: Don't rely on the wrong pending table Marc Zyngier
2019-11-20 16:42 ` [PATCH 20/22] KVM: arm/arm64: Let the timer expire in hardirq context on RT Marc Zyngier
2019-11-20 16:42 ` [PATCH 21/22] KVM: vgic-v4: Track the number of VLPIs per vcpu Marc Zyngier
2019-11-20 16:42 ` [PATCH 22/22] KVM: arm64: Opportunistically turn off WFI trapping when using direct LPI injection Marc Zyngier
2019-11-21 8:58 ` [GIT PULL] KVM/arm updates for 5.5 Paolo Bonzini
2019-11-21 9:06 ` Marc Zyngier
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