From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 27 Nov 2014 11:21:19 -0500 From: Konrad Rzeszutek Wilk To: Borislav Petkov Cc: Boris Ostrovsky , x86@kernel.org, gregkh@linuxfoundation.org, david.vrabel@citrix.com, stable@vger.kernel.org, rshendershot@mchsi.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3.17 100/141] x86, microcode: Fix accessing dis_ucode_ldr on 32-bit Message-ID: <20141127162118.GA24829@konrad-lan.dumpdata.com> References: <20141127091228.GA4828@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141127091228.GA4828@pd.tnic> Sender: linux-kernel-owner@vger.kernel.org List-ID: On Thu, Nov 27, 2014 at 10:12:28AM +0100, Borislav Petkov wrote: > On Wed, Nov 26, 2014 at 07:13:02PM -0800, Boris Ostrovsky wrote: > > I was confusing you: accessing dis_ucode_ldr by virtual address does > > work on PV. But we then fail later, in load_ucode_intel_ap(), because > > it also tries to use __pa_nodebug() which can't be used by PV. > > > > So if accessing dis_ucode_ldr by virtual address is acceptable > > (although I don't think it is?) then we can stick dis_ucode_ldr=1 into > > xen_start_kernel() and then things look OK. > > > > A better solution may be to replace cpuid in x86_guest() with 'return > > pv_info.paravirt_enabled' (or paravirt_enabled(), I guess). I gave > > it a quick spin (32-bit only) and it seems to work. I'll see how my > > overnight tests behave. > > Ok, but let's have a clean design: maybe have a weak default stub which > returns false when PARAVIRT is not enabled in the .config and then add > an override in, say, arch/x86/kernel/paravirt.c which returns true when > running as a guest. Something like that, at least. You are describing 'paravirt_enabled()' :-) > > I can imagine other stuff wanting to use the dynamic checking at runtime > too... > > -- > Regards/Gruss, > Boris. > > Sent from a fat crate under my desk. Formatting is fine. > --