Date: Tue, 06 Dec 2011 00:38:11 +0200
From: Andriy Gapon <avg@FreeBSD.org>
To: Alan Cox <alc@rice.edu>
Cc: Alan Cox <alc@FreeBSD.org>, freebsd-emulation@FreeBSD.org, FreeBSD current <freebsd-current@FreeBSD.org>
Subject: Re: Freeze with 10.0 and VirtualBox {4.1.4|4.1.6|4.1.51r38464}
Message-ID: <4EDD47D3.5010803@FreeBSD.org>
In-Reply-To: <4EDD442C.9030406@rice.edu>
References: <4ECF7440.4070300@entel.upc.edu> <20111126163343.GA9150@reks> "<4ED6AEFE.4010106@FreeBSD.org>" <201111301807.21351.jkim@FreeBSD.org> <60ea779052f025798cf65e18c24b7b31@bluelife.at> <47eb9f9b139dd8c59b050f1670a5f18d@bluelife.at> <7c3c9505867f4528af276a571077b9ce@bluelife.at> <4EDCC1C6.3040109@FreeBSD.org> <ce531a25e601ca82701d259808d7d485@bluelife.at> <4EDCCDA2.5070006@FreeBSD.org> <4EDD0644.5030902@rice.edu> <4EDD3F60.8050601@FreeBSD.org> <4EDD442C.9030406@rice.edu>
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on 06/12/2011 00:22 Alan Cox said the following: > On 12/5/2011 4:02 PM, Andriy Gapon wrote: >> on 05/12/2011 19:58 Alan Cox said the following: >>> On 12/05/2011 07:56, Andriy Gapon wrote: >>>> Pages should be marked busy only for some special occasions, wired pages are >>>> not >>>> normally busy; the correct explanation is quite a bit longer than this, the >>>> comment in the code explains VPO_BUSY as "page is in transit". Right now this >>>> flag doesn't seem tom affect vboxdrv code but it may lead to surprises when >>>> some >>>> parts of code that are incorrect now are re-implemented properly: >>>> http://article.gmane.org/gmane.os.freebsd.devel.emulation/9297 >>> VM_ALLOC_NOOBJ implies that the returned page does not have VPO_BUSY set. From >>> the comment at the head of both vm_page_alloc() and vm_page_alloc_contig(): >>> >>> * VM_ALLOC_NOOBJ page is not associated with an object and >>> * should not have the flag VPO_BUSY set >> Ah, oops, forgot about this. >> >>> With regard to the message that the above link points to, I suspect that the >>> introduction of vm_page_alloc_contig() can be used to address the first problem >>> that you point out. Specifically, one or more OBJT_PHYS vm objects could be >>> created and passed to vm_map_find() and then vm_page_alloc_contig() could be >>> used to fill these vm objects with memory. >> That's exactly what I was trying to do when I encountered a need for >> VM_ALLOC_NOOBJ - my object was not NULL. >> Alan, BTW, is it safe to map an OBJT_PHYS object into the kernel_map and into a >> user map (or a few of them) at the same time? >> > > Yes, it is. Thank you! And another question - what would you recommend as a substitute for vm_page_alloc_contig in FreeBSD versions that do not have it? All I can think of is essentially replicating kmem_alloc_contig + contigmapping and allowing a user-specified object to be used in place of kernel_object. -- Andriy Gapon
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