linux-kernel - Re: x86/fpu/xsave: protection key test failures

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Message-ID: <036bd3d8-d6fb-db0f-c4f1-6b2a4a104191@oracle.com>
Date:   Wed, 26 May 2021 10:50:27 -0500
From:   Dave Kleikamp <dave.kleikamp@...cle.com>
To:     Babu Moger <babu.moger@....com>,
        Dave Hansen <dave.hansen@...el.com>,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
        hpa@...or.com, dave.hansen@...ux.intel.com, luto@...nel.org,
        peterz@...radead.org, shuah@...nel.org, jroedel@...e.de,
        ubizjak@...il.com, viro@...iv.linux.org.uk, jpa@....mail.kapsi.fi,
        fenghua.yu@...el.com, kan.liang@...ux.intel.com,
        akpm@...ux-foundation.org, rppt@...nel.org, Fan_Yang@...u.edu.cn,
        anshuman.khandual@....com, b.thiel@...teo.de, jgross@...e.com,
        keescook@...omium.org, seanjc@...gle.com, mh@...ndium.org,
        sashal@...nel.org, krisman@...labora.com, chang.seok.bae@...el.com,
        0x7f454c46@...il.com, jhubbard@...dia.com, sandipan@...ux.ibm.com,
        ziy@...dia.com, kirill.shutemov@...ux.intel.com,
        suxingxing@...ngson.cn, harish@...ux.ibm.com,
        rong.a.chen@...el.com, linuxram@...ibm.com, bauerman@...ux.ibm.com
Subject: Re: x86/fpu/xsave: protection key test failures

On 5/26/21 10:25 AM, Babu Moger wrote:
> 
> 
> On 5/25/21 7:20 PM, Dave Hansen wrote:
>> On 5/25/21 5:03 PM, Babu Moger wrote:
>>>> What values do PKRU and the shadow have when the test fails?  Is PKRU 0?
>>> It goes back to default value 0x55555554. The test is expecting it to be
>>> 0. Printed them below.
>>>
>>> test_ptrace_of_child()::1346, pkey_reg: 0x0000000055555554 shadow:
>>> 0000000000000000
>>> protection_keys_64: pkey-helpers.h:127: _read_pkey_reg: Assertion
>>> `pkey_reg == shadow_pkey_reg' failed.
>>
>> That's backwards (shadow vs pkru) from what I was expecting.
>>
>> Can you turn on all the debuging?
>>
>> Just compile with -DDEBUG_LEVEL=5
>>
> 
> 
> Copied the logs at https://pastebin.com/gtQiHg8Q

I think this failed early due to the debug code. I have a patch that 
gets around this.

View attachment "selftests_vm_pkeys_fix_assert.patch" of type "text/x-patch" (1616 bytes)