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From: John Hubbard <jhubbard@nvidia.com>
To: "Andrew Morton" <akpm@linux-foundation.org>,
	"Jérôme Glisse" <jglisse@redhat.com>
Cc: <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
	Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
	David Nellans <dnellans@nvidia.com>,
	Evgeny Baskakov <ebaskakov@nvidia.com>,
	Mark Hairgrove <mhairgrove@nvidia.com>,
	Sherry Cheung <SCheung@nvidia.com>,
	Subhash Gutti <sgutti@nvidia.com>
Subject: Re: [HMM 07/16] mm/migrate: new memory migration helper for use with device memory v4
Date: Thu, 16 Mar 2017 17:22:51 -0700	[thread overview]
Message-ID: <d4e8433d-4680-dced-4f11-2f3cc8ebc613@nvidia.com> (raw)
In-Reply-To: <20170316160520.d03ac02474cad6d2c8eba9bc@linux-foundation.org>

On 03/16/2017 04:05 PM, Andrew Morton wrote:
> On Thu, 16 Mar 2017 12:05:26 -0400 Jérôme Glisse <jglisse@redhat.com> wrote:
>
>> +static inline struct page *migrate_pfn_to_page(unsigned long mpfn)
>> +{
>> +	if (!(mpfn & MIGRATE_PFN_VALID))
>> +		return NULL;
>> +	return pfn_to_page(mpfn & MIGRATE_PFN_MASK);
>> +}
>
> i386 allnoconfig:
>
> In file included from mm/page_alloc.c:61:
> ./include/linux/migrate.h: In function 'migrate_pfn_to_page':
> ./include/linux/migrate.h:139: warning: left shift count >= width of type
> ./include/linux/migrate.h:141: warning: left shift count >= width of type
> ./include/linux/migrate.h: In function 'migrate_pfn_size':
> ./include/linux/migrate.h:146: warning: left shift count >= width of type
>

It seems clear that this was never meant to work with < 64-bit pfns:

// migrate.h excerpt:
#define MIGRATE_PFN_VALID	(1UL << (BITS_PER_LONG_LONG - 1))
#define MIGRATE_PFN_MIGRATE	(1UL << (BITS_PER_LONG_LONG - 2))
#define MIGRATE_PFN_HUGE	(1UL << (BITS_PER_LONG_LONG - 3))
#define MIGRATE_PFN_LOCKED	(1UL << (BITS_PER_LONG_LONG - 4))
#define MIGRATE_PFN_WRITE	(1UL << (BITS_PER_LONG_LONG - 5))
#define MIGRATE_PFN_DEVICE	(1UL << (BITS_PER_LONG_LONG - 6))
#define MIGRATE_PFN_ERROR	(1UL << (BITS_PER_LONG_LONG - 7))
#define MIGRATE_PFN_MASK	((1UL << (BITS_PER_LONG_LONG - PAGE_SHIFT)) - 1)

...obviously, there is not enough room for these flags, in a 32-bit pfn.

So, given the current HMM design, I think we are going to have to provide a 32-bit version of these 
routines (migrate_pfn_to_page, and related) that is a no-op, right?

thanks
John Hubbard
NVIDIA

WARNING: multiple messages have this Message-ID (diff)
From: John Hubbard <jhubbard@nvidia.com>
To: "Andrew Morton" <akpm@linux-foundation.org>,
	"Jérôme Glisse" <jglisse@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
	David Nellans <dnellans@nvidia.com>,
	Evgeny Baskakov <ebaskakov@nvidia.com>,
	Mark Hairgrove <mhairgrove@nvidia.com>,
	Sherry Cheung <SCheung@nvidia.com>,
	Subhash Gutti <sgutti@nvidia.com>
Subject: Re: [HMM 07/16] mm/migrate: new memory migration helper for use with device memory v4
Date: Thu, 16 Mar 2017 17:22:51 -0700	[thread overview]
Message-ID: <d4e8433d-4680-dced-4f11-2f3cc8ebc613@nvidia.com> (raw)
In-Reply-To: <20170316160520.d03ac02474cad6d2c8eba9bc@linux-foundation.org>

On 03/16/2017 04:05 PM, Andrew Morton wrote:
> On Thu, 16 Mar 2017 12:05:26 -0400 Jérôme Glisse <jglisse@redhat.com> wrote:
>
>> +static inline struct page *migrate_pfn_to_page(unsigned long mpfn)
>> +{
>> +	if (!(mpfn & MIGRATE_PFN_VALID))
>> +		return NULL;
>> +	return pfn_to_page(mpfn & MIGRATE_PFN_MASK);
>> +}
>
> i386 allnoconfig:
>
> In file included from mm/page_alloc.c:61:
> ./include/linux/migrate.h: In function 'migrate_pfn_to_page':
> ./include/linux/migrate.h:139: warning: left shift count >= width of type
> ./include/linux/migrate.h:141: warning: left shift count >= width of type
> ./include/linux/migrate.h: In function 'migrate_pfn_size':
> ./include/linux/migrate.h:146: warning: left shift count >= width of type
>

It seems clear that this was never meant to work with < 64-bit pfns:

// migrate.h excerpt:
#define MIGRATE_PFN_VALID	(1UL << (BITS_PER_LONG_LONG - 1))
#define MIGRATE_PFN_MIGRATE	(1UL << (BITS_PER_LONG_LONG - 2))
#define MIGRATE_PFN_HUGE	(1UL << (BITS_PER_LONG_LONG - 3))
#define MIGRATE_PFN_LOCKED	(1UL << (BITS_PER_LONG_LONG - 4))
#define MIGRATE_PFN_WRITE	(1UL << (BITS_PER_LONG_LONG - 5))
#define MIGRATE_PFN_DEVICE	(1UL << (BITS_PER_LONG_LONG - 6))
#define MIGRATE_PFN_ERROR	(1UL << (BITS_PER_LONG_LONG - 7))
#define MIGRATE_PFN_MASK	((1UL << (BITS_PER_LONG_LONG - PAGE_SHIFT)) - 1)

...obviously, there is not enough room for these flags, in a 32-bit pfn.

So, given the current HMM design, I think we are going to have to provide a 32-bit version of these 
routines (migrate_pfn_to_page, and related) that is a no-op, right?

thanks
John Hubbard
NVIDIA

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  reply	other threads:[~2017-03-17  0:22 UTC|newest]

Thread overview: 90+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-16 16:05 [HMM 00/16] HMM (Heterogeneous Memory Management) v18 Jérôme Glisse
2017-03-16 16:05 ` Jérôme Glisse
2017-03-16 16:05 ` [HMM 01/16] mm/memory/hotplug: convert device bool to int to allow for more flags v3 Jérôme Glisse
2017-03-16 16:05   ` Jérôme Glisse
2017-03-19 20:08   ` Mel Gorman
2017-03-19 20:08     ` Mel Gorman
2017-03-16 16:05 ` [HMM 02/16] mm/put_page: move ref decrement to put_zone_device_page() Jérôme Glisse
2017-03-16 16:05   ` Jérôme Glisse
2017-03-19 20:08   ` Mel Gorman
2017-03-19 20:08     ` Mel Gorman
2017-03-16 16:05 ` [HMM 03/16] mm/ZONE_DEVICE/free-page: callback when page is freed v3 Jérôme Glisse
2017-03-16 16:05   ` Jérôme Glisse
2017-03-19 20:08   ` Mel Gorman
2017-03-19 20:08     ` Mel Gorman
2017-03-16 16:05 ` [HMM 04/16] mm/ZONE_DEVICE/unaddressable: add support for un-addressable device memory v3 Jérôme Glisse
2017-03-16 16:05   ` Jérôme Glisse
2017-03-19 20:09   ` Mel Gorman
2017-03-19 20:09     ` Mel Gorman
2017-03-16 16:05 ` [HMM 05/16] mm/ZONE_DEVICE/x86: add support for un-addressable device memory Jérôme Glisse
2017-03-16 16:05   ` Jérôme Glisse
2017-03-16 16:05 ` [HMM 06/16] mm/migrate: add new boolean copy flag to migratepage() callback Jérôme Glisse
2017-03-16 16:05   ` Jérôme Glisse
2017-03-19 20:09   ` Mel Gorman
2017-03-19 20:09     ` Mel Gorman
2017-03-16 16:05 ` [HMM 07/16] mm/migrate: new memory migration helper for use with device memory v4 Jérôme Glisse
2017-03-16 16:05   ` Jérôme Glisse
2017-03-16 16:24   ` Reza Arbab
2017-03-16 16:24     ` Reza Arbab
2017-03-16 20:58     ` Balbir Singh
2017-03-16 20:58       ` Balbir Singh
2017-03-16 23:05   ` Andrew Morton
2017-03-16 23:05     ` Andrew Morton
2017-03-17  0:22     ` John Hubbard [this message]
2017-03-17  0:22       ` John Hubbard
2017-03-17  0:45       ` Balbir Singh
2017-03-17  0:45         ` Balbir Singh
2017-03-17  0:57         ` John Hubbard
2017-03-17  0:57           ` John Hubbard
2017-03-17  1:52           ` Jerome Glisse
2017-03-17  1:52             ` Jerome Glisse
2017-03-17  3:32             ` Andrew Morton
2017-03-17  3:32               ` Andrew Morton
2017-03-17  3:42           ` Balbir Singh
2017-03-17  3:42             ` Balbir Singh
2017-03-17  4:51             ` Balbir Singh
2017-03-17  4:51               ` Balbir Singh
2017-03-17  7:17               ` John Hubbard
2017-03-17  7:17                 ` John Hubbard
2017-03-16 16:05 ` [HMM 08/16] mm/migrate: migrate_vma() unmap page from vma while collecting pages Jérôme Glisse
2017-03-16 16:05   ` Jérôme Glisse
2017-03-16 16:05 ` [HMM 09/16] mm/hmm: heterogeneous memory management (HMM for short) Jérôme Glisse
2017-03-16 16:05   ` Jérôme Glisse
2017-03-19 20:09   ` Mel Gorman
2017-03-19 20:09     ` Mel Gorman
2017-03-16 16:05 ` [HMM 10/16] mm/hmm/mirror: mirror process address space on device with HMM helpers Jérôme Glisse
2017-03-16 16:05   ` Jérôme Glisse
2017-03-19 20:09   ` Mel Gorman
2017-03-19 20:09     ` Mel Gorman
2017-03-16 16:05 ` [HMM 11/16] mm/hmm/mirror: helper to snapshot CPU page table v2 Jérôme Glisse
2017-03-16 16:05   ` Jérôme Glisse
2017-03-19 20:09   ` Mel Gorman
2017-03-19 20:09     ` Mel Gorman
2017-03-16 16:05 ` [HMM 12/16] mm/hmm/mirror: device page fault handler Jérôme Glisse
2017-03-16 16:05   ` Jérôme Glisse
2017-03-16 16:05 ` [HMM 13/16] mm/hmm/migrate: support un-addressable ZONE_DEVICE page in migration Jérôme Glisse
2017-03-16 16:05   ` Jérôme Glisse
2017-03-16 16:05 ` [HMM 14/16] mm/migrate: allow migrate_vma() to alloc new page on empty entry Jérôme Glisse
2017-03-16 16:05   ` Jérôme Glisse
2017-03-16 16:05 ` [HMM 15/16] mm/hmm/devmem: device memory hotplug using ZONE_DEVICE Jérôme Glisse
2017-03-16 16:05   ` Jérôme Glisse
2017-03-16 16:05 ` [HMM 16/16] mm/hmm/devmem: dummy HMM device for ZONE_DEVICE memory v2 Jérôme Glisse
2017-03-16 16:05   ` Jérôme Glisse
2017-03-17  6:55   ` Bob Liu
2017-03-17  6:55     ` Bob Liu
2017-03-17 16:53     ` Jerome Glisse
2017-03-17 16:53       ` Jerome Glisse
2017-03-16 20:43 ` [HMM 00/16] HMM (Heterogeneous Memory Management) v18 Andrew Morton
2017-03-16 20:43   ` Andrew Morton
2017-03-16 23:49   ` Jerome Glisse
2017-03-16 23:49     ` Jerome Glisse
2017-03-17  8:29     ` Bob Liu
2017-03-17  8:29       ` Bob Liu
2017-03-17 15:57       ` Jerome Glisse
2017-03-17 15:57         ` Jerome Glisse
2017-03-17  8:39     ` Bob Liu
2017-03-17  8:39       ` Bob Liu
2017-03-17 15:52       ` Jerome Glisse
2017-03-17 15:52         ` Jerome Glisse
2017-03-19 20:09 ` Mel Gorman
2017-03-19 20:09   ` Mel Gorman

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