linux-kernel - Re: Patch "x86: Store a per-cpu shadow copy of CR4" gives VirtualBox 4.3.24 indigestion.

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Message-ID: <34194.1425432514@turing-police.cc.vt.edu>
Date:	Tue, 03 Mar 2015 20:28:34 -0500
From:	Valdis.Kletnieks@...edu
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Ingo Molnar <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Patch "x86: Store a per-cpu shadow copy of CR4" gives VirtualBox 4.3.24 indigestion.

On Tue, 03 Mar 2015 17:08:37 -0800, Andy Lutomirski said:
>
> Are they poking cr4 directly with mov?  Let's see:
>
>     /* Enable the VMX bit in CR4 if necessary. */
>     RTCCUINTREG uCr4 = ASMGetCR4();
>     if (!(uCr4 & X86_CR4_VMXE))
>         ASMSetCR4(uCr4 | X86_CR4_VMXE);
>
> ASMSetCR4 is about what you'd expect.
>
> I deliberately renamed write_cr4 to __write_cr4 to catch this kind of
> thing in anything that uses the asm/ headers, but I can't do anything
> about asm code in out-of-tree modules.

Thanks for the confirmation, I've already updated the tracking bug they
were using for 4.0 issues, and will chase it further with them...

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