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Date:   Fri, 2 Mar 2018 10:07:37 +0100
From:   Joerg Roedel <joro@8bytes.org>
To:     Brian Gerst <brgerst@gmail.com>
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Subject: Re: [PATCH 12/31] x86/entry/32: Add PTI cr3 switch to non-NMI
 entry/exit points
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On Thu, Mar 01, 2018 at 01:24:39PM -0500, Brian Gerst wrote:
> The IF flag only affects external maskable interrupts, not traps or
> faults.  You do need to check CR3 because SYSENTER does not clear TF
> and will immediately cause a debug trap on kernel entry (with user
> CR3) if set.  That is why the code existed before to check for the
> entry stack for debug/NMI.

Yeah, okay, thanks for the clarification. This also means the #DB
handler needs to leave with the same cr3 as it entered. I'll work that
into my patches.

Thanks,

	Joerg