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Date:   Thu, 1 Nov 2018 14:17:27 +0100 (CET)
From:   Thomas Gleixner <tglx@linutronix.de>
To:     Eial Czerwacki <eial@scalemp.com>
cc:     Randy Dunlap <rdunlap@infradead.org>,
        "Shai Fultheim (Shai@ScaleMP.com)" <Shai@ScaleMP.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "broonie@kernel.org" <broonie@kernel.org>,
        "mhocko@suse.cz" <mhocko@suse.cz>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        "linux-next@vger.kernel.org" <linux-next@vger.kernel.org>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "mm-commits@vger.kernel.org" <mm-commits@vger.kernel.org>,
        X86 ML <x86@kernel.org>, 'Oren Twaig' <oren@scalemp.com>
Subject: Re: [PATCH] x86/build: Build VSMP support only if selected
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On Thu, 1 Nov 2018, Eial Czerwacki wrote:

> Greetings,
> 
> On 11/01/2018 12:39 PM, Shai Fultheim (Shai@ScaleMP.com) wrote:
> > On 01/11/18 11:37, Thomas Gleixner wrote:
> > 
> >> VSMP support is built even if CONFIG_X86_VSMP is not set. This leads to a build
> >> breakage when CONFIG_PCI is disabled as well.
> >>
> >> Build VSMP code only when selected.
> > 
> > This patch disables detect_vsmp_box() on systems without CONFIG_X86_VSMP, due to
> > the recent 6da63eb241a05b0e676d68975e793c0521387141.  This is significant
> > regression that will affect significant number of deployments.
> > 
> > We will reply shortly with an updated patch that fix the dependency on pv_irq_ops,
> > and revert to CONFIG_PARAVIRT, with proper protection for CONFIG_PCI.
> > 
> 
> here is the proper patch which fixes the issue on hand:
> >From ebff534f8cfa55d7c3ab798c44abe879f3fbe2b8 Mon Sep 17 00:00:00 2001
> From: Eial Czerwacki <eial@scalemp.com>
> Date: Thu, 1 Nov 2018 15:08:32 +0200
> Subject: [PATCH] x86/build: Build VSMP support only if CONFIG_PCI is
> selected
> 
> vsmp dependency of pv_irq_ops removed some years ago, so now let's clean
> it up from vsmp_64.c.
> 
> In short, "cap & ctl & (1 << 4)" was always returning 0, as such we can
> remove all the PARAVIRT/PARAVIRT_XXL code handling that.
> 
> However, the rest of the code depends on CONFIG_PCI, so fix it accordingly.
> 
> Signed-off-by: Eial Czerwacki <eial@scalemp.com>
> Acked-by: Shai Fultheim <shai@scalemp.com>

Nice cleanup!

Acked-by: Thomas Gleixner <tglx@linutronix.de>