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Message-ID: <20200817084110.2672-2-zhukeqian1@huawei.com>
Date: Mon, 17 Aug 2020 16:41:06 +0800
From: Keqian Zhu <zhukeqian1@...wei.com>
To: <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<kvmarm@...ts.cs.columbia.edu>, <kvm@...r.kernel.org>
CC: Marc Zyngier <maz@...nel.org>, Steven Price <steven.price@....com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
James Morse <james.morse@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
<wanghaibin.wang@...wei.com>, Keqian Zhu <zhukeqian1@...wei.com>
Subject: [RFC PATCH 1/5] KVM: arm64: Document pvtime LPT interface
The "Arm Paravirtualized Time for Arm-Base Systems" specification
DEN 0057A just contains "Stolen Time" now, as the details of "Live
Physical Time" have not been fully agreed.
This introduces a new LPT structure with more understandable fields,
as scale_mult and rscale_mult are symmetrical.
Signed-off-by: Steven Price <steven.price@....com>
Signed-off-by: Keqian Zhu <zhukeqian1@...wei.com>
---
Documentation/virt/kvm/arm/pvtime.rst | 78 ++++++++++++++++++++++++++++++-----
Documentation/virt/kvm/devices/vm.rst | 30 ++++++++++++++
2 files changed, 97 insertions(+), 11 deletions(-)
diff --git a/Documentation/virt/kvm/arm/pvtime.rst b/Documentation/virt/kvm/arm/pvtime.rst
index 94bffe2..fd11915 100644
--- a/Documentation/virt/kvm/arm/pvtime.rst
+++ b/Documentation/virt/kvm/arm/pvtime.rst
@@ -8,14 +8,17 @@ 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.
+KVM/arm64 implements the stolen time and live physical time (LPT) parts of this
+specification by providing some hypervisor service calls to a paravirtualized
+guest. With stolen time support, guest can obtain the amount of time stolen
+from its execution. LPT represents time during which the guest is running and
+it realizes cross-native-frequency migrations.
-Two new SMCCC compatible hypercalls are defined:
+Three new SMCCC compatible hypercalls are defined:
* PV_TIME_FEATURES: 0xC5000020
* PV_TIME_ST: 0xC5000021
+* PV_TIME_LPT: 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
@@ -26,7 +29,8 @@ PV_TIME_FEATURES
============= ======== ==========
Function ID: (uint32) 0xC5000020
PV_call_id: (uint32) The function to query for support.
- Currently only PV_TIME_ST is supported.
+ Currently only PV_TIME_ST and PV_TIME_LPT are
+ supported.
Return value: (int64) NOT_SUPPORTED (-1) or SUCCESS (0) if the relevant
PV-time feature is supported by the hypervisor.
============= ======== ==========
@@ -39,17 +43,23 @@ PV_TIME_ST
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_LPT
+ ============= ======== ==========
+ Function ID: (uint32) 0xC5000022
+ Return value: (int64) IPA of the LPT data structure for this guest.
+ On failure:
+ NOT_SUPPORTED (-1)
+ ============= ======== ==========
-PV_TIME_ST returns the structure for the calling VCPU.
+The IPA returned by PV_TIME_ST and PV_TIME_LPT should be mapped by the guest as
+normal memory with inner and outer write back caching attributes, in the inner
+shareable domain.
Stolen Time
-----------
-The structure pointed to by the PV_TIME_ST hypercall is as follows:
+A total of 16 bytes from the IPA returned are guaranteed to be meaningfully
+filled by the hypervisor. The structure description is as follows:
+-------------+-------------+-------------+----------------------------+
| Field | Byte Length | Byte Offset | Description |
@@ -78,3 +88,49 @@ the region using 64k pages and avoids conflicting attributes with other memory.
For the user space interface see Documentation/virt/kvm/devices/vcpu.rst
section "3. GROUP: KVM_ARM_VCPU_PVTIME_CTRL".
+
+Live Physical Time
+-----------
+
+A total of 48 bytes from the IPA returned are guaranteed to be meaningfully
+filled by the hypervisor. The structure description 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 |
++-----------------+-------------+-------------+----------------------------+
+| sequence_number | 8 | 8 | Bit 0: reserved |
+| | | | Bits 1-63: number of runs, |
+| | | | including the initial run. |
++-----------------+-------------+-------------+----------------------------|
+| native_freq | 4 | 16 | Native frequency |
++-----------------+-------------+-------------+----------------------------|
+| pv_freq | 4 | 20 | Paravirtualized frequency |
+| | | | seen by guest |
++-----------------+-------------+-------------+----------------------------|
+| scale_mult | 8 | 24 | Multiplier to scale native |
+| | | | cycles to PV cycles |
++-----------------+-------------+-------------+----------------------------|
+| rscale_mult | 8 | 32 | Multiplier to reversely |
+| | | | scale PV cycles to native |
+| | | | cycles |
++-----------------+-------------+-------------+----------------------------|
+| fracbits | 4 | 40 | The bits of fraction of |
+| | | | scale_mult |
++-----------------+-------------+-------------+----------------------------|
+| rfracbits | 4 | 44 | The bits of fraction of |
+| | | | rscale_mult |
++-----------------+-------------+-------------+----------------------------|
+
+All values in the structure are stored little-endian.
+
+The structure will be updated by the hypervisor prior to scheduling VCPUs. 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 guest.
+
+For the user space interface see Documentation/virt/kvm/devices/vm.rst
+section "6. GROUP: KVM_ARM_VM_PVTIME_LPT_CTRL".
diff --git a/Documentation/virt/kvm/devices/vm.rst b/Documentation/virt/kvm/devices/vm.rst
index 0aa5b1c..7e5a189 100644
--- a/Documentation/virt/kvm/devices/vm.rst
+++ b/Documentation/virt/kvm/devices/vm.rst
@@ -314,3 +314,33 @@ Allows userspace to query the status of migration mode.
if it is enabled
:Returns: -EFAULT if the given address is not accessible from kernel space;
0 in case of success.
+
+6. GROUP: KVM_ARM_VM_PVTIME_LPT_CTRL
+====================================
+
+:Architectures: ARM64
+
+6.1. ATTRIBUTE: KVM_ARM_VM_PVTIME_LPT_IPA (r/w)
+-----------------------------------------------
+
+Specifies the base address of the live physical time (LPT) structure for this
+guest. The base address must be 64 byte aligned and exist within a valid guest
+memory region. See Documentation/virt/kvm/arm/pvtime.rst for more information
+including the layout of the LPT structure.
+
+Parameters: 64-bit base address
+Returns: -ENXIO: LPT not implemented
+ -EEXIST: Base address already set for this guest
+ -EINVAL: Base address not 64 byte aligned or not within guest memory
+
+6.2. ATTRIBUTE: KVM_ARM_VM_PVTIME_LPT_FREQ (r/w)
+------------------------------------------------
+
+Specifies the paravirtualized (PV) frequency for this guest. The PV frequency
+is independent with native frequency, so we can support cross-native-frequency
+migration.
+
+Parameters: 32-bit PV frequency
+Returns: -ENXIO: LPT not implemented
+ -EEXIST: PV frequency already set for this guest
+ -EINVAL: PV frequency is zero
--
1.8.3.1
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