From: Xiaoyao Li <xiaoyao.li@intel.com>
To: "Yao Yuan" <yuan.yao@intel.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Peter Xu" <peterx@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>
Cc: kvm@vger.kernel.org, yuan.yao@linux.intel.com
Subject: Re: [kvm-unit-tests PATCH 1/1] x86/apic: Fix test_apic_timer_one_shot() random failure
Date: Mon, 29 Apr 2024 15:40:20 +0800 [thread overview]
Message-ID: <9ed124f0-9006-4166-921b-135c3c2c84fd@intel.com> (raw)
In-Reply-To: <20240428022906.373130-1-yuan.yao@intel.com>
On 4/28/2024 10:29 AM, Yao Yuan wrote:
> Explicitly clear TMICT to avoid test_apic_timer_one_shot()
> negative failure.
>
> Clear TMICT to disable any enabled but masked local timer.
> Otherwise timer interrupt may occur after lvtt_handler() is
> set as handler and **before** TDCR or TIMCT is set to new
> value, lead this test failure. Log comes from UEFI mode:
The exact reason is that the new value written to APIC_LVTT unmasks the
timer interrupt and if TMICT has non-zero and small value configured
before (by firmware or whatever) it may get an additional one-shot timer
interrupt before new TMICT being programmed.
> PASS: PV IPIs testing
> PASS: pending nmi
> Got local timer intr before write to TDCR / TMICT
> old tmict:0x989680 old lvtt:0x30020 tsc2 - tsc1 = 0xb68
> ^^^^^^^^ ^^^^^^^
It took me a while to figure out the above 2 two lines are added for
debug yourself.
> FAIL: APIC LVT timer one shot
>
> Fixes: 9f815b293961 ("x86: apic: add LVT timer test")
> Signed-off-by: Yao Yuan <yuan.yao@intel.com>
> ---
> x86/apic.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/x86/apic.c b/x86/apic.c
> index dd7e7834..2052e864 100644
> --- a/x86/apic.c
> +++ b/x86/apic.c
> @@ -480,6 +480,13 @@ static void test_apic_timer_one_shot(void)
> uint64_t tsc1, tsc2;
> static const uint32_t interval = 0x10000;
>
> + /*
> + * clear TMICT to disable any enabled but masked local timer.
> + * Otherwise timer interrupt may occur after lvtt_handler() is
> + * set as handler and **before** TDCR or TIMCT is set to new value,
> + * lead this test failure.
> + */
> + apic_write(APIC_TMICT, 0);
> #define APIC_LVT_TIMER_VECTOR (0xee)
>
> handle_irq(APIC_LVT_TIMER_VECTOR, lvtt_handler);
>
> base-commit: 9cab58249f98adc451933530fd7e618e1856eb94
next prev parent reply other threads:[~2024-04-29 7:40 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-28 2:29 [kvm-unit-tests PATCH 1/1] x86/apic: Fix test_apic_timer_one_shot() random failure Yao Yuan
2024-04-29 7:40 ` Xiaoyao Li [this message]
2024-04-29 8:23 ` Yuan Yao
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