Re: [PATCH 0/9] arm64: Stolen time support

From: zhukeqian <zhukeqian1@huawei.com>
To: Steven Price <steven.price@arm.com>
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>,
	<linux-arm-kernel@lists.infradead.org>,
	Marc Zyngier <maz@kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Will Deacon <will@kernel.org>, <kvmarm@lists.cs.columbia.edu>,
	<xiexiangyou@huawei.com>, <yebiaoxiang@huawei.com>,
	"wanghaibin.wang@huawei.com >> Wanghaibin (D)" 
	<wanghaibin.wang@huawei.com>
Subject: Re: [PATCH 0/9] arm64: Stolen time support
Date: Tue, 21 Jul 2020 11:26:30 +0800	[thread overview]
Message-ID: <1611996b-1ec1-dee7-ed61-b3b9df23f138@huawei.com> (raw)
In-Reply-To: <20190802145017.42543-1-steven.price@arm.com>

Hi Steven,

On 2019/8/2 22:50, Steven Price wrote:
> This series add support for paravirtualized time for arm64 guests and
> KVM hosts following the specification in Arm's document DEN 0057A:
> 
> https://developer.arm.com/docs/den0057/a
> 
> It implements support for stolen time, allowing the guest to
> identify time when it is forcibly not executing.
> 
> It doesn't implement support for Live Physical Time (LPT) as there are
> some concerns about the overheads and approach in the above
Do you plan to pick up LPT support? As there is demand of cross-frequency migration
(from older platform to newer platform).

I am not clear about the overheads and approach problem here, could you please
give some detail information? Maybe we can work together to solve these concerns. :-)

Thanks,
Keqian
> specification, and I expect an updated version of the specification to
> be released soon with just the stolen time parts.
> 
> I previously posted a series including LPT (as well as stolen time):
> https://lore.kernel.org/kvmarm/20181212150226.38051-1-steven.price@arm.com/
> 
> Patches 2, 5, 7 and 8 are cleanup patches and could be taken separately.
> 
> Christoffer Dall (1):
>   KVM: arm/arm64: Factor out hypercall handling from PSCI code
> 
> Steven Price (8):
>   KVM: arm64: Document PV-time interface
>   KVM: arm64: Implement PV_FEATURES call
>   KVM: arm64: Support stolen time reporting via shared structure
>   KVM: Allow kvm_device_ops to be const
>   KVM: arm64: Provide a PV_TIME device to user space
>   arm/arm64: Provide a wrapper for SMCCC 1.1 calls
>   arm/arm64: Make use of the SMCCC 1.1 wrapper
>   arm64: Retrieve stolen time as paravirtualized guest
> 
>  Documentation/virtual/kvm/arm/pvtime.txt | 107 +++++++++++++
>  arch/arm/kvm/Makefile                    |   2 +-
>  arch/arm/kvm/handle_exit.c               |   2 +-
>  arch/arm/mm/proc-v7-bugs.c               |  13 +-
>  arch/arm64/include/asm/kvm_host.h        |  13 +-
>  arch/arm64/include/asm/kvm_mmu.h         |   2 +
>  arch/arm64/include/asm/pvclock-abi.h     |  20 +++
>  arch/arm64/include/uapi/asm/kvm.h        |   6 +
>  arch/arm64/kernel/Makefile               |   1 +
>  arch/arm64/kernel/cpu_errata.c           |  80 ++++------
>  arch/arm64/kernel/kvm.c                  | 155 ++++++++++++++++++
>  arch/arm64/kvm/Kconfig                   |   1 +
>  arch/arm64/kvm/Makefile                  |   2 +
>  arch/arm64/kvm/handle_exit.c             |   4 +-
>  include/kvm/arm_hypercalls.h             |  44 ++++++
>  include/kvm/arm_psci.h                   |   2 +-
>  include/linux/arm-smccc.h                |  58 +++++++
>  include/linux/cpuhotplug.h               |   1 +
>  include/linux/kvm_host.h                 |   4 +-
>  include/linux/kvm_types.h                |   2 +
>  include/uapi/linux/kvm.h                 |   2 +
>  virt/kvm/arm/arm.c                       |  18 +++
>  virt/kvm/arm/hypercalls.c                | 138 ++++++++++++++++
>  virt/kvm/arm/mmu.c                       |  44 ++++++
>  virt/kvm/arm/psci.c                      |  84 +---------
>  virt/kvm/arm/pvtime.c                    | 190 +++++++++++++++++++++++
>  virt/kvm/kvm_main.c                      |   6 +-
>  27 files changed, 848 insertions(+), 153 deletions(-)
>  create mode 100644 Documentation/virtual/kvm/arm/pvtime.txt
>  create mode 100644 arch/arm64/include/asm/pvclock-abi.h
>  create mode 100644 arch/arm64/kernel/kvm.c
>  create mode 100644 include/kvm/arm_hypercalls.h
>  create mode 100644 virt/kvm/arm/hypercalls.c
>  create mode 100644 virt/kvm/arm/pvtime.c
> 