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Re: [kvm-unit-tests PATCH v1 1/4] arm64: split its-trigger test into KVM
From: |
Alexandru Elisei |
Subject: |
Re: [kvm-unit-tests PATCH v1 1/4] arm64: split its-trigger test into KVM and TCG variants |
Date: |
Wed, 28 Apr 2021 15:00:15 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 |
Hi,
On 4/28/21 1:06 PM, Alex Bennée wrote:
> Marc Zyngier <maz@kernel.org> writes:
>
>> On 2021-04-28 11:18, Alex Bennée wrote:
>>> A few of the its-trigger tests rely on IMPDEF behaviour where caches
>>> aren't flushed before invall events. However TCG emulation doesn't
>>> model any invall behaviour and as we can't probe for it we need to be
>>> told. Split the test into a KVM and TCG variant and skip the invall
>>> tests when under TCG.
>>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>>> Cc: Shashi Mallela <shashi.mallela@linaro.org>
>>> ---
>>> arm/gic.c | 60 +++++++++++++++++++++++++++--------------------
>>> arm/unittests.cfg | 11 ++++++++-
>>> 2 files changed, 45 insertions(+), 26 deletions(-)
>>> diff --git a/arm/gic.c b/arm/gic.c
>>> index 98135ef..96a329d 100644
>>> --- a/arm/gic.c
>>> +++ b/arm/gic.c
>>> @@ -36,6 +36,7 @@ static struct gic *gic;
>>> static int acked[NR_CPUS], spurious[NR_CPUS];
>>> static int irq_sender[NR_CPUS], irq_number[NR_CPUS];
>>> static cpumask_t ready;
>>> +static bool under_tcg;
>>> static void nr_cpu_check(int nr)
>>> {
>>> @@ -734,32 +735,38 @@ static void test_its_trigger(void)
>>> /*
>>> * re-enable the LPI but willingly do not call invall
>>> * so the change in config is not taken into account.
>>> - * The LPI should not hit
>>> + * The LPI should not hit. This does however depend on
>>> + * implementation defined behaviour - under QEMU TCG emulation
>>> + * it can quite correctly process the event directly.
>> It looks to me that you are using an IMPDEF behaviour of *TCG*
>> here. The programming model mandates that there is an invalidation
>> if you change the configuration of the LPI.
> But does it mandate that the LPI cannot be sent until the invalidation?
I think Marc is referring to this section of the GIC architecture (Arm IHI
0069F,
page 5-82, I've highlighted the interesting bits):
"A Redistributor can cache the information from the LPI Configuration tables
pointed to by GICR_PROPBASER, when GICR_CTLR.EnableLPI == 1, subject to all of
the
following rules:
* Whether or not one or more caches are present is IMPLEMENTATION DEFINED. Where
at least one cache is present, the structure and size is IMPLEMENTATION DEFINED.
* An LPI Configuration table entry might be allocated into the cache at any
time.
* A cached LPI Configuration table entry is not guaranteed to remain in the
cache.
* A cached LPI Configuration table entry *is not guaranteed to remain incoherent
with memory*.
* A change to the LPI configuration *is not guaranteed to be visible until an
appropriate invalidation operation has completed*"
I interpret that as that an INVALL guarantees that a change is visible, but it
the
change can become visible even without the INVALL.
The test relies on the fact that changes to the LPI tables are not visible
*under
KVM* until the INVALL command, but that's not necessarily the case on real
hardware. To match the spec, I think the test "dev2/eventid=20 still does not
trigger any LPI" should be removed and the stats reset should take place before
the configuration for LPI 8195 is set to the default.
Thanks,
Alex
- [kvm-unit-tests PATCH v1 0/4] enable LPI and ITS for TCG, Alex Bennée, 2021/04/28
- [kvm-unit-tests PATCH v1 2/4] scripts/arch-run: don't use deprecated server/nowait options, Alex Bennée, 2021/04/28
- [kvm-unit-tests PATCH v1 3/4] arm64: enable its-migration tests for TCG, Alex Bennée, 2021/04/28
- [kvm-unit-tests PATCH v1 1/4] arm64: split its-trigger test into KVM and TCG variants, Alex Bennée, 2021/04/28
- Re: [kvm-unit-tests PATCH v1 1/4] arm64: split its-trigger test into KVM and TCG variants, Marc Zyngier, 2021/04/28
- Re: [kvm-unit-tests PATCH v1 1/4] arm64: split its-trigger test into KVM and TCG variants, Alex Bennée, 2021/04/28
- Re: [kvm-unit-tests PATCH v1 1/4] arm64: split its-trigger test into KVM and TCG variants,
Alexandru Elisei <=
- Re: [kvm-unit-tests PATCH v1 1/4] arm64: split its-trigger test into KVM and TCG variants, Marc Zyngier, 2021/04/28
- Re: [kvm-unit-tests PATCH v1 1/4] arm64: split its-trigger test into KVM and TCG variants, Auger Eric, 2021/04/28
- Re: [kvm-unit-tests PATCH v1 1/4] arm64: split its-trigger test into KVM and TCG variants, Alex Bennée, 2021/04/28
- Re: [kvm-unit-tests PATCH v1 1/4] arm64: split its-trigger test into KVM and TCG variants, Alex Bennée, 2021/04/28
- Re: [kvm-unit-tests PATCH v1 1/4] arm64: split its-trigger test into KVM and TCG variants, Marc Zyngier, 2021/04/28
[kvm-unit-tests PATCH v1 4/4] arm64: split its-migrate-unmapped-collection into KVM and TCG variants, Alex Bennée, 2021/04/28