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From: David Laight <David.Laight@ACULAB.COM>
To: 'Vlastimil Babka' <vbabka@suse.cz>,
	Christoph Hellwig <hch@lst.de>,
	Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Baoquan He <bhe@redhat.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"cl@linux.com" <cl@linux.com>,
	"John.p.donnelly@oracle.com" <John.p.donnelly@oracle.com>,
	"kexec@lists.infradead.org" <kexec@lists.infradead.org>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>,
	Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: RE: [PATCH v3 5/5] mm/slub: do not create dma-kmalloc if no managed pages in DMA zone
Date: Wed, 15 Dec 2021 11:51:50 +0000	[thread overview]
Message-ID: <67ff367b7a90452f8c009707a00e67b2@AcuMS.aculab.com> (raw)
In-Reply-To: <f7c1f169-f9b3-6930-f933-d69ab0287069@suse.cz>

From: Vlastimil Babka
> Sent: 15 December 2021 10:34
> 
> On 12/15/21 08:27, Christoph Hellwig wrote:
> > On Wed, Dec 15, 2021 at 07:03:35AM +0000, Hyeonggon Yoo wrote:
> >> I'm not sure that allocating from ZONE_DMA32 instead of ZONE_DMA
> >> for kdump kernel is nice way to solve this problem.
> >
> > What is the problem with zones in kdump kernels?
> 
> My understanding is that kdump kernel can only use physical memory that it
> got reserved by the main kernel, and the main kernel will reserve some block
> of memory that doesn't include any pages from ZONE_DMA (first 16MB of
> physical memory or whatnot). 
...

Is there still any support for any of the very old hardware that could only
support 24bit DMA?

I think the AMD PCnet-ISA and PCnet-PCI ethernet (lance) were both 32bit masters.
(I don't remember ever having to worry about physical addresses.)
I'm sure I remember some old SCSI boards only being able to do 24bit DMA.
But I can't remember which bus interface they were.
Unlikely to be ISA because it has always been hard to get a motherboard
DMA channel into 'cascade mode'.

Might have been some EISA boards - anyone still use those?
So we are left with early PCI boards.

It really is worth looking at what actually needs it at all.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

WARNING: multiple messages have this Message-ID (diff)
From: David Laight <David.Laight@ACULAB.COM>
To: 'Vlastimil Babka' <vbabka@suse.cz>,
	Christoph Hellwig <hch@lst.de>,
	Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Baoquan He <bhe@redhat.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"cl@linux.com" <cl@linux.com>,
	"John.p.donnelly@oracle.com" <John.p.donnelly@oracle.com>,
	"kexec@lists.infradead.org" <kexec@lists.infradead.org>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>,
	Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: RE: [PATCH v3 5/5] mm/slub: do not create dma-kmalloc if no managed pages in DMA zone
Date: Wed, 15 Dec 2021 11:51:50 +0000	[thread overview]
Message-ID: <67ff367b7a90452f8c009707a00e67b2@AcuMS.aculab.com> (raw)
In-Reply-To: <f7c1f169-f9b3-6930-f933-d69ab0287069@suse.cz>

From: Vlastimil Babka
> Sent: 15 December 2021 10:34
> 
> On 12/15/21 08:27, Christoph Hellwig wrote:
> > On Wed, Dec 15, 2021 at 07:03:35AM +0000, Hyeonggon Yoo wrote:
> >> I'm not sure that allocating from ZONE_DMA32 instead of ZONE_DMA
> >> for kdump kernel is nice way to solve this problem.
> >
> > What is the problem with zones in kdump kernels?
> 
> My understanding is that kdump kernel can only use physical memory that it
> got reserved by the main kernel, and the main kernel will reserve some block
> of memory that doesn't include any pages from ZONE_DMA (first 16MB of
> physical memory or whatnot). 
...

Is there still any support for any of the very old hardware that could only
support 24bit DMA?

I think the AMD PCnet-ISA and PCnet-PCI ethernet (lance) were both 32bit masters.
(I don't remember ever having to worry about physical addresses.)
I'm sure I remember some old SCSI boards only being able to do 24bit DMA.
But I can't remember which bus interface they were.
Unlikely to be ISA because it has always been hard to get a motherboard
DMA channel into 'cascade mode'.

Might have been some EISA boards - anyone still use those?
So we are left with early PCI boards.

It really is worth looking at what actually needs it at all.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec

  reply	other threads:[~2021-12-15 11:51 UTC|newest]

Thread overview: 74+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-13 12:27 [PATCH v3 0/5] Avoid requesting page from DMA zone when no managed pages Baoquan He
2021-12-13 12:27 ` Baoquan He
2021-12-13 12:27 ` [PATCH v3 1/5] docs: kernel-parameters: Update to reflect the current default size of atomic pool Baoquan He
2021-12-13 12:27   ` Baoquan He
2021-12-13 14:20   ` john.p.donnelly
2021-12-13 14:20     ` john.p.donnelly
2021-12-13 12:27 ` [PATCH v3 2/5] dma-pool: allow user to disable " Baoquan He
2021-12-13 12:27   ` Baoquan He
2021-12-13 14:21   ` john.p.donnelly
2021-12-13 14:21     ` john.p.donnelly
2021-12-13 12:27 ` [PATCH v3 3/5] mm_zone: add function to check if managed dma zone exists Baoquan He
2021-12-13 12:27   ` Baoquan He
2021-12-13 14:22   ` john.p.donnelly
2021-12-13 14:22     ` john.p.donnelly
2021-12-16 10:52   ` David Hildenbrand
2021-12-16 10:52     ` David Hildenbrand
2021-12-13 12:27 ` [PATCH v3 4/5] dma/pool: create dma atomic pool only if dma zone has managed pages Baoquan He
2021-12-13 12:27   ` Baoquan He
2021-12-13 12:27   ` Baoquan He
2021-12-13 14:23   ` john.p.donnelly
2021-12-13 14:23     ` john.p.donnelly
2021-12-13 14:23     ` john.p.donnelly
2021-12-13 12:27 ` [PATCH v3 5/5] mm/slub: do not create dma-kmalloc if no managed pages in DMA zone Baoquan He
2021-12-13 12:27   ` Baoquan He
2021-12-13 13:43   ` Hyeonggon Yoo
2021-12-13 13:43     ` Hyeonggon Yoo
2021-12-14  5:32     ` Baoquan He
2021-12-14  5:32       ` Baoquan He
2021-12-14 10:09       ` Vlastimil Babka
2021-12-14 10:09         ` Vlastimil Babka
2021-12-14 10:28         ` Christoph Lameter
2021-12-14 10:28           ` Christoph Lameter
2021-12-15  4:48         ` Hyeonggon Yoo
2021-12-15  4:48           ` Hyeonggon Yoo
2021-12-15  7:03           ` Hyeonggon Yoo
2021-12-15  7:03             ` Hyeonggon Yoo
2021-12-15  7:27             ` Christoph Hellwig
2021-12-15  7:27               ` Christoph Hellwig
2021-12-15 10:34               ` Vlastimil Babka
2021-12-15 10:34                 ` Vlastimil Babka
2021-12-15 11:51                 ` David Laight [this message]
2021-12-15 11:51                   ` David Laight
2021-12-15 13:41                 ` Baoquan He
2021-12-15 13:41                   ` Baoquan He
2021-12-17 11:38               ` Hyeonggon Yoo
2021-12-17 11:38                 ` Hyeonggon Yoo
2021-12-20  7:32                 ` Baoquan He
2021-12-20  7:32                   ` Baoquan He
2022-01-07 11:56               ` Hyeonggon Yoo
2022-01-07 11:56                 ` Hyeonggon Yoo
2021-12-15 14:42             ` Baoquan He
2021-12-15 14:42               ` Baoquan He
2021-12-15 10:08         ` Baoquan He
2021-12-15 10:08           ` Baoquan He
2021-12-17 11:38       ` Hyeonggon Yoo
2021-12-17 11:38         ` Hyeonggon Yoo
2021-12-21  8:56         ` Christoph Hellwig
2021-12-21  8:56           ` Christoph Hellwig
2021-12-22 12:37           ` Hyeonggon Yoo
2021-12-22 12:37             ` Hyeonggon Yoo
2021-12-23  8:52             ` Christoph Hellwig
2021-12-23  8:52               ` Christoph Hellwig
2021-12-13 14:24   ` john.p.donnelly
2021-12-13 14:24     ` john.p.donnelly
2021-12-14 16:31   ` Christoph Hellwig
2021-12-14 16:31     ` Christoph Hellwig
2021-12-14 17:07     ` john.p.donnelly
2021-12-14 17:07       ` john.p.donnelly
2021-12-15  7:27       ` Christoph Hellwig
2021-12-15  7:27         ` Christoph Hellwig
2021-12-13 21:05 ` [PATCH v3 0/5] Avoid requesting page from DMA zone when no managed pages Andrew Morton
2021-12-13 21:05   ` Andrew Morton
2021-12-14  0:35   ` Baoquan He
2021-12-14  0:35     ` Baoquan He

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