Commit b74edaf6 authored by Zengruan Ye's avatar Zengruan Ye Committed by Zheng Zengkai
Browse files

KVM: arm64: Document PV-sched interface 



virt inclusion
category: feature
bugzilla: 47624
CVE: NA

--------------------------------

Introduce a paravirtualization interface for KVM/arm64 to PV-sched.

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: default avatarZengruan Ye <yezengruan@huawei.com>
Reviewed-by: default avatarZhanghailiang <zhang.zhanghailiang@huawei.com>
Signed-off-by: default avatarZheng Zengkai <zhengzengkai@huawei.com>
parent c8365281

Documentation/virt/kvm/arm/pvsched.rst

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.. SPDX-License-Identifier: GPL-2.0



Paravirtualized sched support for arm64

=======================================



KVM/arm64 provides some hypervisor service calls to support a paravirtualized

sched.



Some SMCCC compatible hypercalls are defined:



* PV_SCHED_FEATURES:          0xC5000090

* PV_SCHED_IPA_INIT:          0xC5000091

* PV_SCHED_IPA_RELEASE:       0xC5000092



The existence of the PV_SCHED hypercall should be probed using the SMCCC 1.1

ARCH_FEATURES mechanism before calling it.



PV_SCHED_FEATURES

    ============= ========    ==========

    Function ID:  (uint32)    0xC5000090

    PV_call_id:   (uint32)    The function to query for support.

    Return value: (int64)     NOT_SUPPORTED (-1) or SUCCESS (0) if the relevant

                              PV-sched feature is supported by the hypervisor.

    ============= ========    ==========



PV_SCHED_IPA_INIT

    ============= ========    ==========

    Function ID:  (uint32)    0xC5000091

    Return value: (int64)     NOT_SUPPORTED (-1) or SUCCESS (0) if the IPA of

                              this vCPU's PV data structure is shared to the

                              hypervisor.

    ============= ========    ==========



PV_SCHED_IPA_RELEASE

    ============= ========    ==========

    Function ID:  (uint32)    0xC5000092

    Return value: (int64)     NOT_SUPPORTED (-1) or SUCCESS (0) if the IPA of

                              this vCPU's PV data structure is released.

    ============= ========    ==========



PV sched state

--------------



The structure pointed to by the PV_SCHED_IPA hypercall is as follows:



+-----------+-------------+-------------+-----------------------------------+

| Field     | Byte Length | Byte Offset | Description                       |

+===========+=============+=============+===================================+

| preempted |      4      |      0      | Indicates that the vCPU that owns |

|           |             |             | this struct is running or not.    |

|           |             |             | Non-zero values mean the vCPU has |

|           |             |             | been preempted. Zero means the    |

|           |             |             | vCPU is not preempted.            |

+-----------+-------------+-------------+-----------------------------------+



The preempted field will be updated to 0 by the hypervisor prior to scheduling

a vCPU. When the vCPU is scheduled out, the preempted field will be updated

to 1 by the hypervisor.