From: Thomas Gleixner <tglx@linutronix.de>
To: Andrea Arcangeli <aarcange@redhat.com>, Ingo Molnar <mingo@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>,
Rafael Aquini <aquini@redhat.com>,
Waiman Long <longman@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] x86: restore the write back cache of reserved RAM in iounmap()
Date: Thu, 19 Nov 2020 22:01:02 +0100 [thread overview]
Message-ID: <875z61oycx.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20201119175902.17394-2-aarcange@redhat.com>
On Thu, Nov 19 2020 at 12:59, Andrea Arcangeli wrote:
> If reserved memory is mapped with ioremap_noncache() or ioremap_wc(),
> the kernel correctly splits the direct mapping and marks the PAGE_SIZE
> granular region uncached, so both the virtual direct mapping and the
> second virtual mapping in vmap space will be both marked uncached or
> write through (i.e. _PAGE_PCD/PWT set on the pagetable).
>
> However when iounmap is called later, nothing restores the direct
> mapping write back memtype.
Darn. This was discussed in 2008 already and survived that long?
https://lore.kernel.org/lkml/20080205011357.GA14712@linux-os.sc.intel.com/
No idea how that happened to slip through...
Thanks,
tglx
next prev parent reply other threads:[~2020-11-19 21:01 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-19 17:59 [PATCH 0/1] x86: restore the write back cache of reserved RAM in iounmap() Andrea Arcangeli
2020-11-19 17:59 ` [PATCH 1/1] " Andrea Arcangeli
2020-11-19 21:01 ` Thomas Gleixner [this message]
2020-11-19 18:02 ` [PATCH 0/1] " Christoph Hellwig
2020-11-19 19:03 ` Andrea Arcangeli
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