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()
Date: Fri, 19 Jul 2019 23:10:45 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.21.1907192309190.1782@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20190719140122.GF19068@suse.de>
On Fri, 19 Jul 2019, Joerg Roedel wrote:
> On Thu, Jul 18, 2019 at 11:04:57AM +0200, Thomas Gleixner wrote:
> > 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.
>
> Actually there is already a comment in this function explaining why p4d
> and pud don't need any treatment:
>
> /*
> * set_pgd(pgd, *pgd_k); here would be useless on PAE
> * and redundant with the set_pmd() on non-PAE. As would
> * set_p4d/set_pud.
> */
Indeed. Why did I think there was none?
> I couldn't say it with less words :)
It's perfectly fine.
Thanks,
tglx
next prev parent reply other threads:[~2019-07-19 21:10 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-17 7:14 [PATCH 0/3 v2] Sync unmappings in vmalloc/ioremap areas Joerg Roedel
2019-07-17 7:14 ` [PATCH 1/3] x86/mm: Check for pfn instead of page in vmalloc_sync_one() Joerg Roedel
2019-07-17 7:14 ` [PATCH 2/3] x86/mm: Sync also unmappings " Joerg Roedel
2019-07-17 21:06 ` Dave Hansen
2019-07-18 8:44 ` Joerg Roedel
2019-07-17 21:43 ` Thomas Gleixner
2019-07-18 8:46 ` Joerg Roedel
2019-07-18 9:04 ` Thomas Gleixner
2019-07-18 9:25 ` Joerg Roedel
2019-07-19 14:01 ` Joerg Roedel
2019-07-19 21:10 ` Thomas Gleixner [this message]
2019-07-17 7:14 ` [PATCH 3/3] mm/vmalloc: Sync unmappings in vunmap_page_range() Joerg Roedel
2019-07-17 21:24 ` Andy Lutomirski
2019-07-18 9:17 ` Joerg Roedel
2019-07-18 19:04 ` Andy Lutomirski
2019-07-19 12:21 ` Joerg Roedel
2019-07-19 12:24 ` Andy Lutomirski
2019-07-19 13:00 ` Joerg Roedel
-- strict thread matches above, loose matches on Subject: below --
2019-07-15 11:02 [PATCH 0/3] Sync unmappings in vmalloc/ioremap areas Joerg Roedel
2019-07-15 11:02 ` [PATCH 2/3] x86/mm: Sync also unmappings in vmalloc_sync_one() Joerg Roedel
2019-07-15 13:08 ` Thomas Gleixner
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