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From: Toshi Kani <toshi.kani@hp.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com,
	arnd@arndb.de, linux-mm@kvack.org, x86@kernel.org,
	linux-kernel@vger.kernel.org, dave.hansen@intel.com,
	Elliott@hp.com
Subject: Re: [PATCH v3 6/6] x86, mm: Support huge KVA mappings on x86
Date: Tue, 03 Mar 2015 16:14:32 -0700	[thread overview]
Message-ID: <1425424472.17007.191.camel@misato.fc.hp.com> (raw)
In-Reply-To: <20150303144414.9f97ef25ad8aed7d112896bf@linux-foundation.org>

On Tue, 2015-03-03 at 14:44 -0800, Andrew Morton wrote:
> On Tue,  3 Mar 2015 10:44:24 -0700 Toshi Kani <toshi.kani@hp.com> wrote:
 :
> > +
> > +#ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
> > +int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
> > +{
> > +	u8 mtrr;
> > +
> > +	/*
> > +	 * Do not use a huge page when the range is covered by non-WB type
> > +	 * of MTRRs.
> > +	 */
> > +	mtrr = mtrr_type_lookup(addr, addr + PUD_SIZE);
> > +	if ((mtrr != MTRR_TYPE_WRBACK) && (mtrr != 0xFF))
> > +		return 0;
> 
> It would be good to notify the operator in some way when this happens. 
> Otherwise the kernel will run more slowly and there's no way of knowing
> why.  I guess slap a pr_info() in there.  Or maybe pr_warn()?

We only use 4KB mappings today, so this case will not make it run
slowly, i.e. it will be the same as today.  Also, adding a message here
can generate a lot of messages when MTRRs cover a large area.  So, I
think we are fine without a message.

> 
> > +	prot = pgprot_4k_2_large(prot);
> > +
> > +	set_pte((pte_t *)pud, pfn_pte(
> > +		(u64)addr >> PAGE_SHIFT,
> > +		__pgprot(pgprot_val(prot) | _PAGE_PSE)));
> > +
> > +	return 1;
> > +}
> > +
> > +int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
> > +{
> > +	u8 mtrr;
> > +
> > +	/*
> > +	 * Do not use a huge page when the range is covered by non-WB type
> > +	 * of MTRRs.
> > +	 */
> > +	mtrr = mtrr_type_lookup(addr, addr + PMD_SIZE);
> > +	if ((mtrr != MTRR_TYPE_WRBACK) && (mtrr != 0xFF))
> > +		return 0;
> > +
> > +	prot = pgprot_4k_2_large(prot);
> > +
> > +	set_pte((pte_t *)pmd, pfn_pte(
> > +		(u64)addr >> PAGE_SHIFT,
> > +		__pgprot(pgprot_val(prot) | _PAGE_PSE)));
> > +
> > +	return 1;
> > +}
> >
> > +int pud_clear_huge(pud_t *pud)
> > +{
> > +	if (pud_large(*pud)) {
> > +		pud_clear(pud);
> > +		return 1;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +int pmd_clear_huge(pmd_t *pmd)
> > +{
> > +	if (pmd_large(*pmd)) {
> > +		pmd_clear(pmd);
> > +		return 1;
> > +	}
> > +
> > +	return 0;
> > +}
> 
> I didn't see anywhere where the return values of these functions are
> documented.  It's all fairly obvious, but we could help the rearers
> a bit.

Agreed.  I will add function headers with descriptions to the new
functions.

Thanks,
-Toshi 



  reply	other threads:[~2015-03-03 23:15 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-03 17:44 [PATCH v3 0/6] Kernel huge I/O mapping support Toshi Kani
2015-03-03 17:44 ` [PATCH v3 1/6] mm: Change __get_vm_area_node() to use fls_long() Toshi Kani
2015-03-03 17:44 ` [PATCH v3 2/6] lib: Add huge I/O map capability interfaces Toshi Kani
2015-03-03 17:44 ` [PATCH v3 3/6] mm: Change ioremap to set up huge I/O mappings Toshi Kani
2015-03-04 22:09   ` Ingo Molnar
2015-03-04 23:15     ` Toshi Kani
2015-03-03 17:44 ` [PATCH v3 4/6] mm: Change vunmap to tear down huge KVA mappings Toshi Kani
2015-03-03 17:44 ` [PATCH v3 5/6] x86, mm: Support huge I/O mapping capability I/F Toshi Kani
2015-03-03 17:44 ` [PATCH v3 6/6] x86, mm: Support huge KVA mappings on x86 Toshi Kani
2015-03-03 22:44   ` Andrew Morton
2015-03-03 23:14     ` Toshi Kani [this message]
2015-03-04  1:00       ` Andrew Morton
2015-03-04 16:23         ` Toshi Kani
2015-03-04 20:17           ` Ingo Molnar
2015-03-04 21:16             ` Toshi Kani

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