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

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Message-ID: <20110211212352.GA10845@suse.de>
Date:	Fri, 11 Feb 2011 13:23:52 -0800
From:	Greg KH <gregkh@...e.de>
To:	KY Srinivasan <kys@...rosoft.com>
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

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.

thanks,

greg k-h
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