From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: [PATCH 3/3] KVM: PPC: Book3S: Add support for hwrng found on some powernv systems Date: Thu, 03 Oct 2013 08:07:22 +1000 Message-ID: <1380751642.645.71.camel@pasglop> References: <5243F933.7000907@redhat.com> <20131001083426.GB27484@concordia> <20131001083908.GA17294@redhat.com> <1380620338.645.22.camel@pasglop> <524AAFAA.3010801@redhat.com> <20131002050940.GA25363@drongo> <524BDD73.3020106@redhat.com> <1380704789.645.57.camel@pasglop> <668E4650-BC22-4CBF-A282-E7875DF29DB6@suse.de> <3CBF5732-E7EE-4C96-8132-6D7B77270DAF@suse.de> <20131002100224.GF17294@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Alexander Graf , Paolo Bonzini , Paul Mackerras , Michael Ellerman , linux-kernel@vger.kernel.org, mpm@selenic.com, herbert@gondor.hengli.com.au, linuxppc-dev@ozlabs.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, tytso@mit.edu To: Gleb Natapov Return-path: In-Reply-To: <20131002100224.GF17294@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Wed, 2013-10-02 at 13:02 +0300, Gleb Natapov wrote: > Yes, I alluded to it in my email to Paul and Paolo asked also. How this > interface is disabled? Also hwrnd is MMIO in a host why guest needs to > use hypercall instead of emulating the device (in kernel or somewhere > else?). Another things is that on a host hwrnd is protected from > direct userspace access by virtue of been a device, but guest code (event > kernel mode) is userspace as far as hosts security model goes, so by > implementing this hypercall in a way that directly access hwrnd you > expose hwrnd to a userspace unconditionally. Why is this a good idea? BTW. Is this always going to be like this ? Every *single* architectural or design decision we make for our architecture has to be justified 30 times over, every piece of code bike shedded to oblivion for month, etc... ? Do we always have to finally get to some kind of agreement on design, go to the 6 month bike-shedding phase, just to have somebody else come up and start re-questioning the whole original design (without any understanding of our specific constraints of course) ? You guys are the most horrendous community I have ever got to work with. It's simply impossible to get anything done in any reasonable time frame . At this stage, it would have taken us an order of magnitude less time to simply rewrite an entire hypervisor from scratch. This is sad. Ben.