linux-kernel - [PATCH RFC 0/3] Implement guest time scaling in RISC-V KVM

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Message-ID: <20201203121839.308-1-jiangyifei@huawei.com>
Date:   Thu, 3 Dec 2020 20:18:36 +0800
From:   Yifei Jiang <jiangyifei@...wei.com>
To:     <anup.patel@....com>, <atish.patra@....com>,
        <paul.walmsley@...ive.com>, <palmer@...belt.com>,
        <aou@...s.berkeley.edu>, <pbonzini@...hat.com>
CC:     <kvm-riscv@...ts.infradead.org>, <kvm@...r.kernel.org>,
        <linux-riscv@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <victor.zhangxiaofeng@...wei.com>, <wu.wubin@...wei.com>,
        <zhang.zhanghailiang@...wei.com>, <dengkai1@...wei.com>,
        <yinyipeng1@...wei.com>, Yifei Jiang <jiangyifei@...wei.com>
Subject: [PATCH RFC 0/3] Implement guest time scaling in RISC-V KVM

This series implements guest time scaling based on RDTIME instruction
emulation so that we can allow migrating Guest/VM across Hosts with
different time frequency.

Why not through para-virt. From arm's experience[1], para-virt implementation
doesn't really solve the problem for the following two main reasons:
- RDTIME not only be used in linux, but also in firmware and userspace.
- It is difficult to be compatible with nested virtualization.

[1] https://lore.kernel.org/patchwork/cover/1288153/

Yifei Jiang (3):
  RISC-V: KVM: Change the method of calculating cycles to nanoseconds
  RISC-V: KVM: Support dynamic time frequency from userspace
  RISC-V: KVM: Implement guest time scaling

 arch/riscv/include/asm/csr.h            |  3 ++
 arch/riscv/include/asm/kvm_vcpu_timer.h | 13 +++++--
 arch/riscv/kvm/vcpu_exit.c              | 35 +++++++++++++++++
 arch/riscv/kvm/vcpu_timer.c             | 51 ++++++++++++++++++++++---
 4 files changed, 93 insertions(+), 9 deletions(-)

-- 
2.19.1