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From: Zenghui Yu <yuzenghui@huawei.com>
To: Alexandru Elisei <alexandru.elisei@arm.com>,
	<kvm@vger.kernel.org>, <kvmarm@lists.cs.columbia.edu>,
	<drjones@redhat.com>
Cc: <andre.przywara@arm.com>, Eric Auger <eric.auger@redhat.com>
Subject: Re: [kvm-unit-tests PATCH 10/10] arm64: gic: Use IPI test checking for the LPI tests
Date: Thu, 26 Nov 2020 17:30:31 +0800	[thread overview]
Message-ID: <a7069b1d-ef11-7504-644c-8d341fa2aabc@huawei.com> (raw)
In-Reply-To: <20201125155113.192079-11-alexandru.elisei@arm.com>

On 2020/11/25 23:51, Alexandru Elisei wrote:
> The reason for the failure is that the test "dev2/eventid=20 now triggers
> an LPI" triggers 2 LPIs, not one. This behavior was present before this
> patch, but it was ignored because check_lpi_stats() wasn't looking at the
> acked array.
> 
> I'm not familiar with the ITS so I'm not sure if this is expected, if the
> test is incorrect or if there is something wrong with KVM emulation.

I think this is expected, or not.

Before INVALL, the LPI-8195 was already pending but disabled. On
receiving INVALL, VGIC will reload configuration for all LPIs targeting
collection-3 and deliver the now enabled LPI-8195. We'll therefore see
and handle it before sending the following INT (which will set the
LPI-8195 pending again).

> Did some more testing on an Ampere eMAG (fast out-of-order cores) using
> qemu and kvmtool and Linux v5.8, here's what I found:
> 
> - Using qemu and gic.flat built from*master*: error encountered 864 times
>    out of 1088 runs.
> - Using qemu: error encountered 852 times out of 1027 runs.
> - Using kvmtool: error encountered 8164 times out of 10602 runs.

If vcpu-3 hadn't seen and handled LPI-8195 as quickly as possible (e.g.,
vcpu-3 hadn't been scheduled), the following INT will set the already
pending LPI-8195 pending again and we'll receive it *once* on vcpu-3.
And we won't see the mentioned failure.

I think we can just drop the (meaningless and confusing?) INT.


Thanks,
Zenghui

WARNING: multiple messages have this Message-ID (diff)
From: Zenghui Yu <yuzenghui@huawei.com>
To: Alexandru Elisei <alexandru.elisei@arm.com>,
	<kvm@vger.kernel.org>, <kvmarm@lists.cs.columbia.edu>,
	<drjones@redhat.com>
Cc: andre.przywara@arm.com
Subject: Re: [kvm-unit-tests PATCH 10/10] arm64: gic: Use IPI test checking for the LPI tests
Date: Thu, 26 Nov 2020 17:30:31 +0800	[thread overview]
Message-ID: <a7069b1d-ef11-7504-644c-8d341fa2aabc@huawei.com> (raw)
In-Reply-To: <20201125155113.192079-11-alexandru.elisei@arm.com>

On 2020/11/25 23:51, Alexandru Elisei wrote:
> The reason for the failure is that the test "dev2/eventid=20 now triggers
> an LPI" triggers 2 LPIs, not one. This behavior was present before this
> patch, but it was ignored because check_lpi_stats() wasn't looking at the
> acked array.
> 
> I'm not familiar with the ITS so I'm not sure if this is expected, if the
> test is incorrect or if there is something wrong with KVM emulation.

I think this is expected, or not.

Before INVALL, the LPI-8195 was already pending but disabled. On
receiving INVALL, VGIC will reload configuration for all LPIs targeting
collection-3 and deliver the now enabled LPI-8195. We'll therefore see
and handle it before sending the following INT (which will set the
LPI-8195 pending again).

> Did some more testing on an Ampere eMAG (fast out-of-order cores) using
> qemu and kvmtool and Linux v5.8, here's what I found:
> 
> - Using qemu and gic.flat built from*master*: error encountered 864 times
>    out of 1088 runs.
> - Using qemu: error encountered 852 times out of 1027 runs.
> - Using kvmtool: error encountered 8164 times out of 10602 runs.

If vcpu-3 hadn't seen and handled LPI-8195 as quickly as possible (e.g.,
vcpu-3 hadn't been scheduled), the following INT will set the already
pending LPI-8195 pending again and we'll receive it *once* on vcpu-3.
And we won't see the mentioned failure.

I think we can just drop the (meaningless and confusing?) INT.


Thanks,
Zenghui
_______________________________________________
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https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

  reply	other threads:[~2020-11-26  9:30 UTC|newest]

Thread overview: 78+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-25 15:51 [kvm-unit-tests PATCH 00/10] GIC fixes and improvements Alexandru Elisei
2020-11-25 15:51 ` Alexandru Elisei
2020-11-25 15:51 ` [kvm-unit-tests PATCH 01/10] lib: arm/arm64: gicv3: Add missing barrier when sending IPIs Alexandru Elisei
2020-11-25 15:51   ` Alexandru Elisei
2020-12-01 16:37   ` Auger Eric
2020-12-01 16:37     ` Auger Eric
2020-12-01 17:37     ` Alexandru Elisei
2020-12-01 17:37       ` Alexandru Elisei
2020-11-25 15:51 ` [kvm-unit-tests PATCH 02/10] lib: arm/arm64: gicv2: " Alexandru Elisei
2020-11-25 15:51   ` Alexandru Elisei
2020-12-01 16:37   ` Auger Eric
2020-12-01 16:37     ` Auger Eric
2020-11-25 15:51 ` [kvm-unit-tests PATCH 03/10] arm/arm64: gic: Remove memory synchronization from ipi_clear_active_handler() Alexandru Elisei
2020-11-25 15:51   ` Alexandru Elisei
2020-12-01 16:37   ` Auger Eric
2020-12-01 16:37     ` Auger Eric
2020-12-02 14:02     ` Alexandru Elisei
2020-12-02 14:02       ` Alexandru Elisei
2020-12-02 14:14       ` Alexandru Elisei
2020-12-02 14:14         ` Alexandru Elisei
2020-12-03  9:41         ` Auger Eric
2020-12-03  9:41           ` Auger Eric
2020-11-25 15:51 ` [kvm-unit-tests PATCH 04/10] arm/arm64: gic: Remove unnecessary synchronization with stats_reset() Alexandru Elisei
2020-11-25 15:51   ` Alexandru Elisei
2020-12-01 16:48   ` Auger Eric
2020-12-01 16:48     ` Auger Eric
2020-12-02 14:06     ` Alexandru Elisei
2020-12-02 14:06       ` Alexandru Elisei
2020-12-03 13:10   ` Auger Eric
2020-12-03 13:10     ` Auger Eric
2020-11-25 15:51 ` [kvm-unit-tests PATCH 05/10] arm/arm64: gic: Use correct memory ordering for the IPI test Alexandru Elisei
2020-11-25 15:51   ` Alexandru Elisei
2020-12-03 13:10   ` Auger Eric
2020-12-03 13:10     ` Auger Eric
2020-12-03 13:21     ` Alexandru Elisei
2020-12-03 13:21       ` Alexandru Elisei
2020-11-25 15:51 ` [kvm-unit-tests PATCH 06/10] arm/arm64: gic: Check spurious and bad_sender in the active test Alexandru Elisei
2020-11-25 15:51   ` Alexandru Elisei
2020-12-03 13:10   ` Auger Eric
2020-12-03 13:10     ` Auger Eric
2020-11-25 15:51 ` [kvm-unit-tests PATCH 07/10] arm/arm64: gic: Wait for writes to acked or spurious to complete Alexandru Elisei
2020-11-25 15:51   ` Alexandru Elisei
2020-12-03 13:21   ` Auger Eric
2020-12-03 13:21     ` Auger Eric
2020-11-25 15:51 ` [kvm-unit-tests PATCH 08/10] arm/arm64: gic: Split check_acked() into two functions Alexandru Elisei
2020-11-25 15:51   ` Alexandru Elisei
2020-12-03 13:39   ` Auger Eric
2020-12-03 13:39     ` Auger Eric
2020-12-10 14:45     ` Alexandru Elisei
2020-12-10 14:45       ` Alexandru Elisei
2020-12-15 13:58       ` Auger Eric
2020-12-15 13:58         ` Auger Eric
2020-12-16 11:40         ` Alexandru Elisei
2020-12-16 11:40           ` Alexandru Elisei
2020-12-16 12:37           ` Auger Eric
2020-12-16 12:37             ` Auger Eric
2020-11-25 15:51 ` [kvm-unit-tests PATCH 09/10] arm/arm64: gic: Make check_acked() more generic Alexandru Elisei
2020-11-25 15:51   ` Alexandru Elisei
2020-12-03 14:59   ` Auger Eric
2020-12-03 14:59     ` Auger Eric
2020-11-25 15:51 ` [kvm-unit-tests PATCH 10/10] arm64: gic: Use IPI test checking for the LPI tests Alexandru Elisei
2020-11-25 15:51   ` Alexandru Elisei
2020-11-26  9:30   ` Zenghui Yu [this message]
2020-11-26  9:30     ` Zenghui Yu
2020-11-27 14:50     ` Alexandru Elisei
2020-11-27 14:50       ` Alexandru Elisei
2020-11-30 13:59       ` Zenghui Yu
2020-11-30 13:59         ` Zenghui Yu
2020-11-30 14:19         ` Alexandru Elisei
2020-11-30 14:19           ` Alexandru Elisei
2020-12-01 15:09           ` Alexandru Elisei
2020-12-01 15:09             ` Alexandru Elisei
2020-11-30 17:48     ` Auger Eric
2020-11-30 17:48       ` Auger Eric
2020-12-03 14:59   ` Auger Eric
2020-12-03 14:59     ` Auger Eric
2020-12-09 10:29     ` Alexandru Elisei
2020-12-09 10:29       ` Alexandru Elisei

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