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Date:   Thu, 18 Jul 2019 11:04:57 +0200 (CEST)
From:   Thomas Gleixner <tglx@linutronix.de>
To:     Joerg Roedel <jroedel@suse.de>
cc:     Joerg Roedel <joro@8bytes.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 2/3] x86/mm: Sync also unmappings in vmalloc_sync_one()
In-Reply-To: <20190718084654.GF13091@suse.de>
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References: <20190717071439.14261-1-joro@8bytes.org> <20190717071439.14261-3-joro@8bytes.org> <alpine.DEB.2.21.1907172337590.1778@nanos.tec.linutronix.de> <20190718084654.GF13091@suse.de>
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Joerg,

On Thu, 18 Jul 2019, Joerg Roedel wrote:
> On Wed, Jul 17, 2019 at 11:43:43PM +0200, Thomas Gleixner wrote:
> > On Wed, 17 Jul 2019, Joerg Roedel wrote:
> > > +
> > > +	if (!pmd_present(*pmd_k))
> > > +		return NULL;
> > >  	else
> > >  		BUG_ON(pmd_pfn(*pmd) != pmd_pfn(*pmd_k));
> > 
> > So in case of unmap, this updates only the first entry in the pgd_list
> > because vmalloc_sync_all() will break out of the iteration over pgd_list
> > when NULL is returned from vmalloc_sync_one().
> > 
> > I'm surely missing something, but how is that supposed to sync _all_ page
> > tables on unmap as the changelog claims?
> 
> No, you are right, I missed that. It is a bug in this patch, the code
> that breaks out of the loop in vmalloc_sync_all() needs to be removed as
> well. Will do that in the next version.

I assume that p4d/pud do not need the pmd treatment, but a comment
explaining why would be appreciated.

Thanks,

	tglx