linux-kernel - Re: [PATCH] ix86: really make user_mode() work correctly for VM86 mode

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Date:	Fri, 29 May 2015 09:49:15 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Jan Beulich <JBeulich@...e.com>, "H. Peter Anvin" <hpa@...or.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ix86: really make user_mode() work correctly for VM86
 mode


* Andy Lutomirski <luto@...capital.net> wrote:

> On May 28, 2015 1:16 AM, "Jan Beulich" <JBeulich@...e.com> wrote:
> >
> > While commit efa7045103 ("x86/asm/entry: Make user_mode() work
> > correctly if regs came from VM86 mode") claims that "user_mode() is now
> > identical to user_mode_vm()", this wasn't actually the case - no prior
> > commit made it so.
> 
> That's embarrassing!  I'm not sure how I screwed that up.

I should have noticed it too :-/

In fact I remember that I wanted to double check it all because the algorithmic 
complexity of the new test looked suspiciously too simple on the 32-bit side (we 
_did_ have a legitimate reason to keep the API split originally) - but forgot 
about it.

> Acked-by: Andy Lutomirski <luto@...nel.org>
> 
> This is needed for x86/urgent.

Yeah, queued it up.

> [...]  I'll see if I can write a simple test case, too.  My old do_bounds test 
> should be a good start.

That kind of test would be absolutely fantastic to have.

Thanks,

	Ingo
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