linux-kernel - Re: [Intel IOMMU 05/10] Intel IOMMU driver

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Message-ID: <20070626162909.GD3374@linux-os.sc.intel.com>
Date:	Tue, 26 Jun 2007 09:29:09 -0700
From:	"Keshavamurthy, Anil S" <anil.s.keshavamurthy@...el.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Christoph Lameter <clameter@....com>,
	"Keshavamurthy, Anil S" <anil.s.keshavamurthy@...el.com>,
	linux-kernel@...r.kernel.org, ak@...e.de, gregkh@...e.de,
	muli@...ibm.com, suresh.b.siddha@...el.com, arjan@...ux.intel.com,
	ashok.raj@...el.com, davem@...emloft.net
Subject: Re: [Intel IOMMU 05/10] Intel IOMMU driver

On Mon, Jun 25, 2007 at 11:32:49PM -0700, Andrew Morton wrote:
> On Tue, 19 Jun 2007 16:32:23 -0700 (PDT) Christoph Lameter <clameter@....com> wrote:
> 
> > On Tue, 19 Jun 2007, Keshavamurthy, Anil S wrote:
> > 
> > > +static inline void *alloc_pgtable_page(void)
> > > +{
> > > +	return (void *)get_zeroed_page(GFP_ATOMIC);
> > > +}
> > 
> > Need to pass gfp_t parameter. Repeates a couple of times.
> > ...
> > Is it not possible here to drop the lock and do the alloc with GFP_KERNEL 
> > and deal with the resulting race? That is done in other parts of the 
> > kernel.
> > ...
> > This may be able to become a GFP_KERNEL alloc since interrupts are enabled 
> > at this point?
> > ...
> > GFP_KERNEL alloc possible?
> > 
> 
> Yeah, if there are any callsites at all at which we know that we can
> perform a sleeping allocation, Christoph's suggestions should be adopted. 
> Because even a bare GFP_NOIO is heaps more robust than GFP_ATOMIC, and it
> will also reload the free-pages reserves, making subsequent GFP_ATOMIC
> allocations more likely to succeed.
Yup, will do as part of making this code work for IA64, which is my next
item in my todo list.

-Anil
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