From: Wei Yang <weiyang@linux.vnet.ibm.com>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Wei Yang <weiyang@linux.vnet.ibm.com>,
benh@kernel.crashing.org, paulus@samba.org,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] powerpc/iommu: use iommu_num_pages() to calculate the number of iommu page
Date: Fri, 2 Oct 2015 06:51:59 +0800 [thread overview]
Message-ID: <20151001225159.GA6145@Richards-MBP.lan> (raw)
In-Reply-To: <1443672945.3058.0.camel@ellerman.id.au>
On Thu, Oct 01, 2015 at 02:15:45PM +1000, Michael Ellerman wrote:
>On Thu, 2015-10-01 at 07:50 +0800, Wei Yang wrote:
>> Hmm... some comments on this one? like it or not?
>
>It sounds like it's fixing a bug, but you don't really say. Have you seen this
>fail in the wild?
Hmm... as described in the commit log, this would be a bug when
PAGE_SIZE is much smaller than IOMMU Page Size. This configuration doesn't
happen on current platform. So I didn't see this failure yet.
>
>Which commit introduced the breakage?
Hmm... maybe we could say it is 'commit d084775738b7
<powerpc/iommu: Update the generic code to use dynamic iommu page sizes>'.
>From this commit, powerpc iommu supports dynamic iommu page size.
Before this commit, the size is aligned with PAGE_SIZE, so the value after
shift would be non-zero. After this commit, when PAGE_SIZE is smaller than
the IOMMU Page Size, shift right will make the size 0.
>
>cheers
>
--
Richard Yang
Help you, Help me
next prev parent reply other threads:[~2015-10-01 22:53 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-19 13:04 [PATCH] powerpc/iommu: use iommu_num_pages() to calculate the number of iommu page Wei Yang
2015-09-30 23:50 ` Wei Yang
2015-10-01 4:15 ` Michael Ellerman
2015-10-01 22:51 ` Wei Yang [this message]
2015-11-12 2:32 ` Wei Yang
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