Re: [git pull] changes for tip, and a nasty x86 page table bug

Steven Rostedt
2009-02-20T02:08:54Z

On Thu, 19 Feb 2009, Linus Torvalds wrote:

>
>
> On Thu, 19 Feb 2009, Steven Rostedt wrote:
> >
> > In doing this change, I stumbled upon a nasty bug in the page handling
> > of the x86 code, where we can fall into a state where the PTE
> > has the RW bit set, but the PMD does not.
>
> How do we ever have a PMD that is read-only? That sounds like a bug to
> begin with. There's no reason to ever do that.

Patch 2/6 explains how this happened, and supplies the fix.

>
> In fact, it should trigger the pmd_bad() tests if it ever happens,
> wouldn't it? We want all the _KERNPG_TABLE bits to always be set, no?

I'm not sure what would do a pmd_bad check.

-- Steve