From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail.skyhub.de ([5.9.137.197]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1gxARP-0005tE-Rf for kexec@lists.infradead.org; Fri, 22 Feb 2019 13:00:37 +0000 Date: Fri, 22 Feb 2019 14:00:26 +0100 From: Borislav Petkov Subject: Re: [PATCHv7] x86/kdump: bugfix, make the behavior of crashkernel=X consistent with kaslr Message-ID: <20190222130026.GA30766@zn.tnic> References: <20190205081552.GG21801@zn.tnic> <20190206120804.GC10062@dhcp-128-65.nay.redhat.com> <20190211204816.GB21473@dhcp-128-65.nay.redhat.com> <20190215102458.GD10433@zn.tnic> <20190218014820.GA10711@dhcp-128-65.nay.redhat.com> <20190220083241.GA3447@zn.tnic> <20190220094146.GA8597@dhcp-128-65.nay.redhat.com> <20190221171321.GD12997@zn.tnic> <20190222021101.GA11654@dhcp-128-65.nay.redhat.com> <20190222084241.GC8380@suse.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190222084241.GC8380@suse.de> 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: Joerg Roedel , Dave Young Cc: Randy Dunlap , bhe@redhat.com, konrad.wilk@oracle.com, x86@kernel.org, kexec@lists.infradead.org, Jerry Hoemann , Pingfan Liu , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, Mike Rapoport , Andrew Morton , yinghai@kernel.org, vgoyal@redhat.com On Fri, Feb 22, 2019 at 09:42:41AM +0100, Joerg Roedel wrote: > The current default of 256MB was found by experiments on a bigger > number of machines, to create a reasonable default that is at least > likely to be sufficient of an average machine. Exactly, and this is what makes sense. The code should try the requested reservation and if it fails, it should try high allocation with default swiotlb size because we need to reserve *some* range. If that reservation succeeds, we should say something along the lines of "... requested range failed, reserved range instead." And then in Documentation/admin-guide/kernel-parameters.txt above the crashkernel= explanations, the allocation strategy of best effort should be explained in short. That the kernel will try to allocate high if the requested allocation didn't succeed and that the user can tweak the allocation with the below options. Bottom line is: the kernel should assist the user and try harder to allocate *some* range for a crash kernel when there's no detailed specification what that range should be. *If* the user adds ,low, high, then the kernel should try only that specified range because the assumption is that the user knows what she's doing. But if the user simply wants a range for a crash kernel without stating where that range should be in particular and it's placement is a don't care - as long as there is a range - then the kernel should simply try high, etc. Makes sense? -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply. _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec