From: Dave Hansen <dave.hansen@intel.com>
To: Dave Kleikamp <dave.kleikamp@oracle.com>,
Babu Moger <babu.moger@amd.com>,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org
Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com,
luto@kernel.org, peterz@infradead.org, shuah@kernel.org,
jroedel@suse.de, ubizjak@gmail.com, viro@zeniv.linux.org.uk,
jpa@git.mail.kapsi.fi, fenghua.yu@intel.com,
kan.liang@linux.intel.com, akpm@linux-foundation.org,
rppt@kernel.org, Fan_Yang@sjtu.edu.cn, anshuman.khandual@arm.com,
b.thiel@posteo.de, jgross@suse.com, keescook@chromium.org,
seanjc@google.com, mh@glandium.org, sashal@kernel.org,
krisman@collabora.com, chang.seok.bae@intel.com,
0x7f454c46@gmail.com, jhubbard@nvidia.com,
sandipan@linux.ibm.com, ziy@nvidia.com,
kirill.shutemov@linux.intel.com, suxingxing@loongson.cn,
harish@linux.ibm.com, rong.a.chen@intel.com, linuxram@us.ibm.com,
bauerman@linux.ibm.com
Subject: Re: x86/fpu/xsave: protection key test failures
Date: Tue, 25 May 2021 15:28:56 -0700 [thread overview]
Message-ID: <c7016a57-062a-a9f6-10dc-aafd9c8eb19f@intel.com> (raw)
In-Reply-To: <18af2b84-b350-6bde-9aef-c0266d604e4a@oracle.com>
On 5/25/21 3:22 PM, Dave Kleikamp wrote:
> On 5/25/21 5:18 PM, Dave Hansen wrote:
>> What values do PKRU and the shadow have when the test fails? Is PKRU 0?
>> Any idea how xfeatures&0x200 got clear?
>
> I did observe that PKRU is 0 right before the failure.
>
> Shouldn't this still be a valid value?
It's architecturall *valid* in the hardware for sure, but nothing in the
tests or the kernel should ever set PKRU=0. The selftest is noticing
that it ends up at a value that's entirely unexpected and properly
bugging out.
The reason I'm suspecting an XRSTOR is that the kernel always calls
XRSTOR(RFBM=-1)
setting all of the bits in the Requested Feature BitMap (RFBM). If
RFBM[X]=1 and XSTATE_BV[i]=0 (XSTATE_BV is 'xfeatures' in the traces),
then the state component is set to its initial configuration, which for
PKRU is 0.
That's why I'm asking how xfeatures&0x200 got clear.
next prev parent reply other threads:[~2021-05-25 22:29 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-25 21:37 x86/fpu/xsave: protection key test failures Babu Moger
2021-05-25 22:18 ` Dave Hansen
2021-05-25 22:22 ` Dave Kleikamp
2021-05-25 22:28 ` Dave Hansen [this message]
2021-05-26 0:03 ` Babu Moger
2021-05-26 0:20 ` Dave Hansen
2021-05-26 15:25 ` Babu Moger
2021-05-26 15:50 ` Dave Kleikamp
2021-05-26 16:06 ` Dave Hansen
2021-05-26 17:03 ` Babu Moger
2021-05-26 0:36 ` Andy Lutomirski
2021-05-26 21:14 ` Babu Moger
2021-05-26 21:17 ` Andy Lutomirski
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