linux-kernel - Re: [PATCH] selftests: iommu: add config needed for iommufd_fail

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Message-ID: <2cb86abd-1c28-4916-8763-9f4e6863bf94@oracle.com>
Date: Wed, 27 Mar 2024 18:33:15 +0000
From: Joao Martins <joao.m.martins@...cle.com>
To: Muhammad Usama Anjum <usama.anjum@...labora.com>,
        Jason Gunthorpe <jgg@...pe.ca>, Nicolin Chen <nicolinc@...dia.com>
Cc: kernel@...labora.com, iommu@...ts.linux.dev,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kevin Tian <kevin.tian@...el.com>, Shuah Khan <shuah@...nel.org>
Subject: Re: [PATCH] selftests: iommu: add config needed for iommufd_fail_nth

On 27/03/2024 18:17, Muhammad Usama Anjum wrote:
> On 3/27/24 11:09 PM, Joao Martins wrote:
>> On 27/03/2024 17:49, Muhammad Usama Anjum wrote:
>>> On 3/27/24 7:59 PM, Joao Martins wrote:
>>>> On 27/03/2024 11:49, Jason Gunthorpe wrote:
>>>>> On Wed, Mar 27, 2024 at 03:14:25PM +0500, Muhammad Usama Anjum wrote:
>>>>>> On 3/26/24 8:03 PM, Jason Gunthorpe wrote:
>>>>>>> On Tue, Mar 26, 2024 at 06:09:34PM +0500, Muhammad Usama Anjum wrote:
>>>>>>>> Even after applying this config patch and following snippet (which doesn't
>>>>>>>> terminate the program if mmap doesn't allocate exactly as the hint), I'm
>>>>>>>> finding failed tests.
>>>>>>>>
>>>>>>>> @@ -1746,7 +1748,7 @@ FIXTURE_SETUP(iommufd_dirty_tracking)
>>>>>>>>         assert((uintptr_t)self->buffer % HUGEPAGE_SIZE == 0);
>>>>>>>>         vrc = mmap(self->buffer, variant->buffer_size, PROT_READ | PROT_WRITE,
>>>>>>>>                    mmap_flags, -1, 0);
>>>>>>>> -       assert(vrc == self->buffer);
>>>>>>>> +       assert(vrc == self->buffer);// ???
>>>>>>>>
>>>>>>>> On x86:
>>>>>>>> # Totals: pass:176 fail:4 xfail:0 xpass:0 skip:0 error:0
>>>>>>>> On ARM64:
>>>>>>>> # Totals: pass:166 fail:14 xfail:0 xpass:0 skip:0 error:0
>>>>>>>>
>>>>>>>> The log files are attached.
>>>>>>>
>>>>>>> You probably don't have enough transparent huge pages available to the process
>>>>>>>
>>>>>>>       echo 1024 > /proc/sys/vm/nr_hugepages
>>>>>> After making huge pages available, the iommufd test always passed on x86.
>>>>>> But there are still failures on arm64. I'm looking into the failures.
>>>>>
>>>>> Oh that is really strange. Joao? Nicolin?
>>>>>
>>>> Definitely strange, I'll have a look.
>>>>
>>>> So it set the expected number of dirty bits as that assert doesn't fail, but it
>>>> is failing when we check that even bits are set but not odd ones. Like it's
>>>> hasn't set those bits.
>>>>
>>>> For mock tests there should be no difference between x86 and ARM assuming the
>>>> typical 4K page-size. Maybe this is 64k base pages in ARM? That's the only thing
>>>> that I can think of that affected mock domain.
>>> The config is attached. The defaults are being used i.e., 4k page.
>>
>> Looks like CONFIG_IOMMUFD_DRIVER is not defined :(
> I'll retest with this config and update the patch to include it in the
> config fragment needed for this test. Once we add all required config
> options in config fragment, the test should never fail. Somehow this gets
> included in the x86, but not on ARM.

The option is automatically selected by an user of iova_bitmap_set(). x86 has
AMD and Intel IOMMUs which use it and auto selected (ARM64 doesn't yet, but soon
to be a reality). Some vfio drivers get it auto-selected it as well.

But I forgot to do the same thing for iommufd-test kconfig in commit a9af47e382a
("iommufd/selftest: Test IOMMU_HWPT_GET_DIRTY_BITMAP") where mock domain also
uses iova_bitmap_set(). So your patch is likely not the right place to set
CONFIG_IOMMUFD_DRIVER=y.

See Jason's snip on auto-selecting if IOMMUFD_TEST is set.