Re: [PATCH 00/11] Introduce support for RISC-V architecture

From: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
To: "Stanisław Kardach" <kda@semihalf.com>
Cc: Frank Zhao <Frank.Zhao@starfivetech.com>,
	Sam Grove <sam.grove@sifive.com>, Marcin Wojtas <mw@semihalf.com>,
	upstream@semihalf.com, dev <dev@dpdk.org>
Subject: Re: [PATCH 00/11] Introduce support for RISC-V architecture
Date: Thu, 12 May 2022 23:06:38 +0200	[thread overview]
Message-ID: <441757d5-bce9-2f75-9088-87601f22fa4e@canonical.com> (raw)
In-Reply-To: <CALVGJWKNBAs2b+Dh82+22JJUrwduYBgezd9=o0gdZ3YtnW15qw@mail.gmail.com>

On 5/12/22 15:56, Stanisław Kardach wrote:
> On Thu, May 12, 2022 at 11:46 AM Heinrich Schuchardt
> <heinrich.schuchardt@canonical.com> wrote:
> <snip>
>> The above failures for performance tests without a bound NIC can be
>> reproduced on x86_64. So this is not RISC-V specific.
>>
>> With both ports of an Intel Corporation Ethernet Controller 10-Gigabit
>> X540-AT2 bound to the sfio-pci driver some fast tests fail on the
>> Unmatched board:
>>
>>    16/173 DPDK:fast-tests / eal_flags_n_opt_autotest FAIL 5.54s (exit
>> status 255 or signal 127 SIGinvalid)
>>   >>> DPDK_TEST=eal_flags_n_opt_autotest MALLOC_PERTURB_=31
>> build/app/test/dpdk-test --file-prefix=eal_flags_n_opt_autotest
>>    18/173 DPDK:fast-tests / eal_flags_no_huge_autotest FAIL 5.31s (exit
>> status 255 or signal 127 SIGinvalid)
>>   >>> DPDK_TEST=eal_flags_no_huge_autotest MALLOC_PERTURB_=150
>> build/app/test/dpdk-test --file-prefix=eal_flags_no_huge_autotest
>>    21/173 DPDK:fast-tests / eal_flags_vdev_opt_autotest FAIL 5.38s (exit
>> status 255 or signal 127 SIGinvalid)
>>   >>> MALLOC_PERTURB_=71 DPDK_TEST=eal_flags_vdev_opt_autotest
>> build/app/test/dpdk-test --file-prefix=eal_flags_vdev_opt_autotest
>>    25/173 DPDK:fast-tests / eal_flags_misc_autotest FAIL 5.58s (exit
>> status 255 or signal 127 SIGinvalid)
>>   >>> DPDK_TEST=eal_flags_misc_autotest MALLOC_PERTURB_=130
>> build/app/test/dpdk-test --file-prefix=eal_flags_misc_autotest
>>
>> The eal* tests succeed on x86_64 with a bound Intel I211 NIC.
> The common element of those tests is --no-huge flag. The reason why
> they are failing is a combination of --no-huge and a lack of IOMMU
> (VT-d on Intel). Lack of IOMMU means that DMA will be done using
> physical addresses (RTE_IOVA_PA), however that implicitly requires
> hugepages to function. More details are in [1]. That mail also shows
> how to replicate the same issue on x86 even without a device bound to
> UIO.
> The following fails:
>    $ ./app/test/dpdk-test --iova-mode=pa --no-huge
> But this works:
>    sudo ./app/test/dpdk-test --iova-mode=pa
> However fixing it is not as straightforward as I thought (some tests
> are not run where they should - [3]). As I explain in [2], the PCI bus
> probing may force RTE_IOVA_PA on no-IOMMU platforms. That gives the
> same effect as passing `--iova-mode=pa`. If no PCI device is bound,
> then DPDK will be in RTE_IOVA_DC mode and that works just fine with
> --no-huge.
> 
> As DPDK CI does not bind any device for fast-tests I've concluded that
> it is the way those tests should be run. If not then I'm not sure how
> should I handle --iova-mode=pa + --no-huge in general. Any
> suggestions?

Thanks for your analysis and explanation. The respective tests should 
return TEST_SKIPPED if called with an unsupported parameter combination.

According to your analysis this is not a problem specific to the RISC-V 
series but can be resolved separately.

Maybe you could add a note in doc/guides/rel_notes/known_issues.rst.

Best regards

Heinrich

> 
> [1] http://mails.dpdk.org/archives/dev/2021-June/210773.html
> [2] http://mails.dpdk.org/archives/dev/2021-June/211146.html
> [3] https://patches.dpdk.org/project/dpdk/patch/20210604141601.275430-4-kda@semihalf.com/
> 
>>
>> If the eal* tests are run depends on the installed Linux packages. I
>> have used 'apt build-dep dpdk' on Ubuntu Jammy to install prerequisite
>> packages before building DPDK.
>>
>> Best regards
>>
>> Heinrich
>>