linux-kernel - Re: [PATCH 2/3] x86/mm: Sync also unmappings in vmalloc_sync

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Message-ID: <20190718092533.GH13091@suse.de>
Date:   Thu, 18 Jul 2019 11:25:33 +0200
From:   Joerg Roedel <jroedel@...e.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Joerg Roedel <joro@...tes.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 2/3] x86/mm: Sync also unmappings in vmalloc_sync_one()

On Thu, Jul 18, 2019 at 11:04:57AM +0200, Thomas Gleixner wrote:
> On Thu, 18 Jul 2019, Joerg Roedel wrote:
> > 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.

Yes, p4d and pud don't need to be handled here, as the code is 32-bit
only and there p4d is folded anyway. Pud is only relevant for PAE and
will already be mapped when the page-table is created (for performance
reasons, because pud is top-level at PAE and mapping it later requires a
TLB flush).
The pud with PAE also never changes during the life-time of the
page-table because we can't map a huge-page there. I will put that into
a comment.

Thanks,

	Joerg