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Date:   Mon, 11 May 2020 01:03:21 -0400
From:   Sasha Levin <sashal@kernel.org>
To:     Andi Kleen <ak@linux.intel.com>
Cc:     Vegard Nossum <vegard.nossum@oracle.com>,
        linux-kernel@vger.kernel.org, tglx@linutronix.de, luto@kernel.org,
        tony.luck@intel.com, chang.seok.bae@intel.com
Subject: Re: [PATCH v10 00/18] Enable FSGSBASE instructions
Message-ID: <20200511050321.GO13035@sasha-vm>
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On Sun, May 10, 2020 at 05:50:28PM -0700, Andi Kleen wrote:
>> So this is a check that checks if you're running in user mode if
>> you have a debug trap with single step, but somehow it triggered
>> for a user segment.
>>
>> Probably the regs got corrupted.
>>
>> Sasha, I suspect you're missing a mov %rsp,%rdi somewhere in the
>> debug entry path that sets up the regs argument for the C code.
>
>... Ah never mind. Thomas has a better explanation.

FWIW, this series was heavily tested for the past few months to the
point that we're comfortable in enabling it for 3rd party users on
Azure:
https://bugs.launchpad.net/ubuntu/+source/linux-azure/+bug/1877425.

-- 
Thanks,
Sasha