From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from eu-smtp-delivery-151.mimecast.com ([185.58.85.151]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mxSp8-000ezM-QH for kexec@lists.infradead.org; Wed, 15 Dec 2021 11:51:56 +0000 From: David Laight 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 Message-ID: <67ff367b7a90452f8c009707a00e67b2@AcuMS.aculab.com> References: <20211213122712.23805-1-bhe@redhat.com> <20211213122712.23805-6-bhe@redhat.com> <20211213134319.GA997240@odroid> <20211214053253.GB2216@MiWiFi-R3L-srv> <20211215044818.GB1097530@odroid> <20211215070335.GA1165926@odroid> <20211215072710.GA3010@lst.de> In-Reply-To: MIME-Version: 1.0 Content-Language: en-US List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: 'Vlastimil Babka' , Christoph Hellwig , Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Baoquan He , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "akpm@linux-foundation.org" , "cl@linux.com" , "John.p.donnelly@oracle.com" , "kexec@lists.infradead.org" , "stable@vger.kernel.org" , Pekka Enberg , David Rientjes , Joonsoo Kim 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