From: Nicholas Piggin <npiggin@gmail.com>
To: Christoph Hellwig <hch@lst.de>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH 2/5] kernel/dma: remove unnecessary unmap_kernel_range
Date: Thu, 28 Jan 2021 09:44:15 +1000 [thread overview]
Message-ID: <1611790740.civn6atbwp.astroid@bobo.none> (raw)
In-Reply-To: <20210127071059.GA21133@lst.de>
Excerpts from Christoph Hellwig's message of January 27, 2021 5:10 pm:
> On Tue, Jan 26, 2021 at 05:08:46PM -0500, Konrad Rzeszutek Wilk wrote:
>> On Tue, Jan 26, 2021 at 02:54:01PM +1000, Nicholas Piggin wrote:
>> > vunmap will remove ptes.
>>
>> Should there be some ASSERT after the vunmap to make sure that is the
>> case?
>
> Not really. removing the PTEs is the whole point of vunmap. Everything
> else is just house keeping.
Agree. I did double check this and wrote a quick test to check ptes were
there before the vunmap and cleared after, just to make sure I didn't
make a silly mistake with the patch. But in general drivers should be
able to trust code behind the API call will do the right thing. Such
assertions should go in the vunmap() implementation as appropriate.
Thanks,
Nick
WARNING: multiple messages have this Message-ID (diff)
From: Nicholas Piggin <npiggin@gmail.com>
To: Christoph Hellwig <hch@lst.de>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Robin Murphy <robin.murphy@arm.com>,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/5] kernel/dma: remove unnecessary unmap_kernel_range
Date: Thu, 28 Jan 2021 09:44:15 +1000 [thread overview]
Message-ID: <1611790740.civn6atbwp.astroid@bobo.none> (raw)
In-Reply-To: <20210127071059.GA21133@lst.de>
Excerpts from Christoph Hellwig's message of January 27, 2021 5:10 pm:
> On Tue, Jan 26, 2021 at 05:08:46PM -0500, Konrad Rzeszutek Wilk wrote:
>> On Tue, Jan 26, 2021 at 02:54:01PM +1000, Nicholas Piggin wrote:
>> > vunmap will remove ptes.
>>
>> Should there be some ASSERT after the vunmap to make sure that is the
>> case?
>
> Not really. removing the PTEs is the whole point of vunmap. Everything
> else is just house keeping.
Agree. I did double check this and wrote a quick test to check ptes were
there before the vunmap and cleared after, just to make sure I didn't
make a silly mistake with the patch. But in general drivers should be
able to trust code behind the API call will do the right thing. Such
assertions should go in the vunmap() implementation as appropriate.
Thanks,
Nick
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iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2021-01-27 23:47 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-26 4:53 [PATCH 0/5] mm/vmalloc: cleanup after hugepage series Nicholas Piggin
2021-01-26 4:54 ` [PATCH 1/5] mm/vmalloc: remove map_kernel_range Nicholas Piggin
2021-01-26 6:37 ` Christoph Hellwig
2021-01-26 4:54 ` [PATCH 2/5] kernel/dma: remove unnecessary unmap_kernel_range Nicholas Piggin
2021-01-26 4:54 ` Nicholas Piggin
2021-01-26 6:38 ` Christoph Hellwig
2021-01-26 6:38 ` Christoph Hellwig
2021-01-26 22:08 ` Konrad Rzeszutek Wilk
2021-01-26 22:08 ` Konrad Rzeszutek Wilk
2021-01-27 7:10 ` Christoph Hellwig
2021-01-27 7:10 ` Christoph Hellwig
2021-01-27 23:44 ` Nicholas Piggin [this message]
2021-01-27 23:44 ` Nicholas Piggin
2021-01-26 4:54 ` [PATCH 3/5] powerpc/xive: " Nicholas Piggin
2021-01-26 4:54 ` Nicholas Piggin
2021-01-26 6:38 ` Christoph Hellwig
2021-01-26 6:38 ` Christoph Hellwig
2021-01-26 7:25 ` Cédric Le Goater
2021-01-26 7:25 ` Cédric Le Goater
2021-01-26 4:54 ` [PATCH 4/5] mm/vmalloc: remove unmap_kernel_range Nicholas Piggin
2021-01-26 6:38 ` Christoph Hellwig
2021-01-26 4:54 ` [PATCH 5/5] mm/vmalloc: improve allocation failure error messages Nicholas Piggin
2021-01-26 6:39 ` Christoph Hellwig
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