linux-kernel - Re: [PATCH v3 0/3] LoongArch: KVM: Remove SW timer switch when vcpu is halt polling

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Message-ID: <008ec0db-0c3e-0ed6-3f85-cfc60e5e696a@loongson.cn>
Date:   Tue, 14 Nov 2023 09:47:00 +0800
From:   maobibo <maobibo@...ngson.cn>
To:     Huacai Chen <chenhuacai@...nel.org>
Cc:     Tianrui Zhao <zhaotianrui@...ngson.cn>,
        WANG Xuerui <kernel@...0n.name>, kvm@...r.kernel.org,
        loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/3] LoongArch: KVM: Remove SW timer switch when vcpu
 is halt polling



On 2023/11/13 下午10:36, Huacai Chen wrote:
> Hi, Bibo,
> 
> Does this series have some relationship with the commit
> "LoongArch:LSVZ: set timer offset at first time once" in our internal
> repo?

No, it is not relative with internal repo. This patch is only 
optimization for timer save and restore. The internal repo is to set 
timestamp offset for VM.

I will post another patch for timestamp offset setting.

Regards
Bibo,

> 
> Huacai
> 
> On Fri, Nov 10, 2023 at 5:07 PM Bibo Mao <maobibo@...ngson.cn> wrote:
>>
>> This patches removes SW timer switch during vcpu block stage. VM uses HW
>> timer rather than SW PV timer on LoongArch system, it can check pending
>> HW timer interrupt status directly, rather than switch to SW timer and
>> check injected SW timer interrupt.
>>
>> When SW timer is not used in vcpu halt-polling mode, the relative
>> SW timer handling before entering guest can be removed also. Timer
>> emulation is simpler than before, SW timer emuation is only used in vcpu
>> thread context switch.
>>
>> ---
>>
>> Changes in v3:
>>    Add kvm_arch_vcpu_runnable checking before kvm_vcpu_halt.
>>
>> Changes in v2:
>>    Add halt polling support for idle instruction emulation, using api
>> kvm_vcpu_halt rather than kvm_vcpu_block in function kvm_emu_idle.
>>
>> ---
>>
>> Bibo Mao (3):
>>    LoongArch: KVM: Remove SW timer switch when vcpu is halt polling
>>    LoongArch: KVM: Allow to access HW timer CSR registers always
>>    LoongArch: KVM: Remove kvm_acquire_timer before entering guest
>>
>>   arch/loongarch/include/asm/kvm_vcpu.h |  1 -
>>   arch/loongarch/kvm/exit.c             | 13 ++------
>>   arch/loongarch/kvm/main.c             |  1 -
>>   arch/loongarch/kvm/timer.c            | 47 +++++++--------------------
>>   arch/loongarch/kvm/vcpu.c             | 38 +++++-----------------
>>   5 files changed, 22 insertions(+), 78 deletions(-)
>>
>>
>> base-commit: 305230142ae0637213bf6e04f6d9f10bbcb74af8
>> --
>> 2.39.3
>>