Messages in this thread | | | Date | Sat, 10 May 2008 16:19:27 +1000 | From | "Dave Airlie" <> | Subject | Re: [git head] X86_PAT & mprotect |
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On Sat, May 10, 2008 at 8:20 AM, Pallipadi, Venkatesh <venkatesh.pallipadi@intel.com> wrote: > > > > >-----Original Message----- > >From: Dave Airlie [mailto:airlied@gmail.com] > >Sent: Friday, May 09, 2008 3:11 PM > >To: Pallipadi, Venkatesh > >Cc: Ingo Molnar; Hugh Dickins; Frans Pop; Barnes, Jesse; > >linux-kernel@vger.kernel.org; Packard, Keith; Yinghai Lu; > >Andrew Morton; Linus Torvalds; H. Peter Anvin; Thomas > >Gleixner; Nick Piggin; Jesse Barnes > >Subject: Re: [git head] X86_PAT & mprotect > > > >On Sat, May 10, 2008 at 6:05 AM, Venki Pallipadi > ><venkatesh.pallipadi@intel.com> wrote: > >> On Fri, May 09, 2008 at 12:08:18PM +0200, Ingo Molnar wrote: > >> > > >> > * Venki Pallipadi <venkatesh.pallipadi@intel.com> wrote: > >> > > >> > > > I've tried doing it slightly differently below, don't > >know whether > >> > > > you'll consider it an improvement or not. > >> > > > >> > > Hugh: Thanks for looking into this. Yes. I like your > >modified patch. > >> > > Simpler and smaller. > >> > > >> > i have stuck your original patch into testing and nothing > >blew up so > >> > far. Due to the mm/ bits this is not for the scope of x86.git, but > >> > obviously it all looks good and is .26-worthy to me: > >> > > >> > Acked-by: Ingo Molnar <mingo@elte.hu> > >> > Tested-by: Ingo Molnar <mingo@elte.hu> > >> > > >> > Venki, could you please send a full patch against -git that has > >> > everything from Hugh included, with an updated changelog, for > >> > Linus/Andrew to ack/apply? > >> > > >> > >> Ingo, > >> > >> Split up the patch into two parts as the pci part was > >unrelated to mprotect > >> problem in a sense. > >> > >> Here is the first patch. > >> > >> Thanks, > >> Venki > >> > >> > >> Some versions of X used the mprotect workaround to change > >caching type from > >> > >> UC to WB, so that it can then use mtrr to program WC for > >that region [1]. > >> Change the mmap of pci space through /sys or /proc > >interfaces from UC to > >> UC_MINUS. With this change, X will not need to use mprotect > >> workaround to get WC type. > >> Also the bug with mprotect which lets caller to change PAT > >bits is fixed in > >> the follow on patch. So, this X workaround will stop > >working as well. > >> > > > >Wow this kinda puts X in a nasty position, we have 2.6.25 and > >previous kernels > >where we use the original /sys interfaces and nasty hack to > >workaround, but on 2.6.26 we magically need to > >switch to the /sys _uc interfaces or the users X will slow down. > > > > No. With 2.6.26 you can still use same /sys resource file, without > the mprotect workaround and set the MTRR as before. > > The change from UC to UC_MINUS in this patch ensures that the > X drivers MTRR will take precedence and X does not need any mprotect > hacks. >
Cool just making sure.
Keithp, I hope we didn't error check the mremap return values :)
Dave.
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