linux-kernel - Re: [PATCH v3 0/6] KVM: LoongArch: selftests: Add timer test case

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Message-ID: <CAAhV-H4xprj-WmMkp86xEmn4NL3wwW3aaDoMj=SUiP3pEa+Q7g@mail.gmail.com>
Date: Mon, 24 Nov 2025 10:03:48 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Bibo Mao <maobibo@...ngson.cn>
Cc: "open list:LOONGARCH" <loongarch@...ts.linux.dev>, Paolo Bonzini <pbonzini@...hat.com>, 
	Sean Christopherson <seanjc@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/6] KVM: LoongArch: selftests: Add timer test case

On Mon, Nov 24, 2025 at 9:58 AM Bibo Mao <maobibo@...ngson.cn> wrote:
>
>
>
> On 2025/11/21 下午10:08, Huacai Chen wrote:
> > Hi, Bibo,
> >
> > On Thu, Nov 20, 2025 at 2:58 PM Bibo Mao <maobibo@...ngson.cn> wrote:
> >>
> >> This patchset adds timer test case for LoongArch system, it is based
> >> on common arch_timer test case. And it includes one-shot and period mode
> >> timer interrupt test, software emulated timer function and time counter
> >> test.
> > I test this series on top of 6.18-rc6 with Loongson-3A5000, sometimes
> > it passes, sometimes I get:
> > [root@...ora kvm]# ./arch_timer
> > Random seed: 0x6b8b4567
> > Guest assert failed,  vcpu 2; stage; 0; iter: 1
> > ==== Test Assertion Failure ====
> >    loongarch/arch_timer.c:79: irq_iter == 0
> >    pid=60138 tid=60142 errno=4 - Interrupted system call
> >       1  0x00000001200037cf: test_vcpu_run 于 arch_timer.c:70
> >       2  0x00007ffff2449f27: ?? ??:0
> >       3  0x00007ffff24c0633: ?? ??:0
> >    irq_iter = 0x1.
> >    Guest period timer interrupt was not triggered within the specified
> >    interval, try to increase the error margin by [-e] option.
> >
> > Is this as expected, or something is wrong?
> There is problem with that. In generic the vCPU task is rescheduled on
> other CPUs or preempted, so period timer interrupt is not handled in
> specified time.
Then this series need to be updated, or problem comes from other places?

Huacai

>
> Regards
> Bibo Mao
> >
> > Hucai
> >
> >> ---
> >> v2 ... v3:
> >>    1. Adjust order about patch 2 and patch 3
> >>    2. Add test case with alphabetical order
> >>    3. Merge one-shot and period timer interrupt test case into one
> >>    4. Only add LoongArch specific modification with common file
> >>       Makefile.kvm
> >>
> >> v1 ... v2:
> >>    1. Restore PC and PRMD after exception handler
> >>    2. Split patch 4 into two small patches with period timer test and
> >>       time counter test
> >>    3. With time counter test, set time count with 0 when create VM. And
> >>       verify time count starts from 0 in guest code
> >> ---
> >> Bibo Mao (6):
> >>    KVM: LoongArch: selftests: Add system registers save and restore on
> >>      exception
> >>    KVM: LoongArch: selftests: Add basic interfaces
> >>    KVM: LoongArch: selftests: Add exception handler register interface
> >>    KVM: LoongArch: selftests: Add timer interrupt test case
> >>    KVM: LoongArch: selftests: Add SW emulated timer test
> >>    KVM: LoongArch: selftests: Add time counter test
> >>
> >>   tools/testing/selftests/kvm/Makefile.kvm      |   1 +
> >>   .../kvm/include/loongarch/arch_timer.h        |  84 ++++++++
> >>   .../kvm/include/loongarch/processor.h         |  81 +++++++-
> >>   .../selftests/kvm/lib/loongarch/exception.S   |   6 +
> >>   .../selftests/kvm/lib/loongarch/processor.c   |  47 ++++-
> >>   .../selftests/kvm/loongarch/arch_timer.c      | 194 ++++++++++++++++++
> >>   6 files changed, 410 insertions(+), 3 deletions(-)
> >>   create mode 100644 tools/testing/selftests/kvm/include/loongarch/arch_timer.h
> >>   create mode 100644 tools/testing/selftests/kvm/loongarch/arch_timer.c
> >>
> >>
> >> base-commit: 23cb64fb76257309e396ea4cec8396d4a1dbae68
> >> --
> >> 2.39.3
> >>
>