linux-kernel - RE: [PATCH 1/3]: Staging: hv: Use native page allocation/free functions

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Date:	Fri, 11 Feb 2011 21:37:23 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Greg KH <gregkh@...e.de>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"virtualization@...ts.osdl.org" <virtualization@...ts.osdl.org>,
	Hank Janssen <hjanssen@...rosoft.com>
Subject: RE: [PATCH 1/3]: Staging: hv: Use native page allocation/free
 functions



> -----Original Message-----
> From: Greg KH [mailto:gregkh@...e.de]
> Sent: Friday, February 11, 2011 4:24 PM
> To: KY Srinivasan
> Cc: linux-kernel@...r.kernel.org; devel@...uxdriverproject.org;
> virtualization@...ts.osdl.org; Hank Janssen
> Subject: Re: [PATCH 1/3]: Staging: hv: Use native page allocation/free functions
> 
> On Fri, Feb 11, 2011 at 08:55:56PM +0000, KY Srinivasan wrote:
> >
> >
> > > -----Original Message-----
> > > From: Greg KH [mailto:gregkh@...e.de]
> > > Sent: Friday, February 11, 2011 1:30 PM
> > > To: KY Srinivasan
> > > Cc: linux-kernel@...r.kernel.org; devel@...uxdriverproject.org;
> > > virtualization@...ts.osdl.org; Hank Janssen
> > > Subject: Re: [PATCH 1/3]: Staging: hv: Use native page allocation/free
> functions
> > >
> > > On Fri, Feb 11, 2011 at 09:59:00AM -0800, K. Y. Srinivasan wrote:
> > > > --- a/drivers/staging/hv/hv.c
> > > > +++ b/drivers/staging/hv/hv.c
> > > > @@ -230,7 +230,12 @@ int hv_init(void)
> > > >  	* Allocate the hypercall page memory
> > > >  	* virtaddr = osd_page_alloc(1);
> > > >  	*/
> > > > -	virtaddr = osd_virtual_alloc_exec(PAGE_SIZE);
> > > > +#ifdef __x86_64__
> > > > +	virtaddr = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL_EXEC);
> > > #else
> > > > +	virtaddr =  __vmalloc(PAGE_SIZE, GFP_KERNEL,
> > > > +			__pgprot(__PAGE_KERNEL & (~_PAGE_NX))); #endif
> > >
> > > I'm not saying this patch is wrong at all, but I still don't understand why this is
> > > different depending on the architecture of the machine.  Why is this
> necessary, it
> > > should be ok to do the same type of allocation no matter what the processor
> is,
> > > right?
> >
> > You are right Greg; I don't think there is a need to specify different page
> > protection bits based on the architecture - PAGE_KERNEL_EXEC should be
> enough.
> 
> I thought so, but for some reason Hank said there this was needed.
> Hank, is it still true?
> 
> > However, this is the code that is currently in the tree - refer to osd.c.
> 
> Oh, I remember, it's not a critique of this patch, it just reminded me
> of this question I always had for this code.
> 
> > If it is ok with you, I could submit an additional patch to clean this up.
> 
> If Hank says it is ok, and you all test it to verify nothing breaks,
> please send it on.
Will do; the new patch will be on top of the 3 patch sequence I sent earlier today.

Regards,

K. Y
> 
> thanks,
> 
> greg k-h

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