From: Christoph Helwig <hch@lst.de>
To: Joe Jin <joe.jin@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
"DONGLI.ZHANG" <dongli.zhang@oracle.com>,
konrad@kernel.org, Christoph Helwig <hch@lst.de>,
John Sobecki <john.sobecki@oracle.com>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] xen-swiotlb: exchange memory with Xen only when pages are contiguous
Date: Fri, 26 Oct 2018 09:48:02 +0200 [thread overview]
Message-ID: <20181026074802.GA4768@lst.de> (raw)
In-Reply-To: <5b64850f-9142-0360-fe4e-9e7bc74d2368@oracle.com>
On Thu, Oct 25, 2018 at 11:56:02AM -0700, Joe Jin wrote:
> I just discussed this patch with Boris in private, his opinions(Boris,
> please correct me if any misunderstood) are:
>
> 1. With/without the check, both are incorrect, he thought we need to
> prevented unalloc'd free at here.
> 2. On freeing, if upper layer already checked the memory was DMA-able,
> the checking at here does not make sense, we can remove all checks.
> 3. xen_create_contiguous_region() and xen_destroy_contiguous_region()
> to come in pairs.
>
> For #1 and #3, I think we need something associate it, like a list, on
> allocating, add addr to it, on freeing, check if in the list.
Is there any way to figure out based on an address if the exchange
operation happened?
> For #2, I'm was not found anywhere validated the address on
> dma_free_coherent() callpath, not just xen-swiotlb.
At least for simple direct mappings there is no easy way to verify that
without keeping a list, and for some of the ops that do vmap like
operations we have basic santiy checks, but nothing that really catches
a wrong free.
next prev parent reply other threads:[~2018-10-26 7:48 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-24 3:09 [PATCH] xen-swiotlb: exchange memory with Xen only when pages are contiguous Joe Jin
2018-10-24 13:02 ` Konrad Rzeszutek Wilk
2018-10-24 13:57 ` Boris Ostrovsky
2018-10-24 14:43 ` Joe Jin
2018-10-25 11:45 ` Boris Ostrovsky
2018-10-25 14:23 ` Joe Jin
2018-10-25 16:10 ` Boris Ostrovsky
2018-10-25 16:28 ` Joe Jin
2018-10-25 18:56 ` Joe Jin
2018-10-26 7:48 ` Christoph Helwig [this message]
2018-10-26 8:54 ` Dongli Zhang
2018-10-26 14:48 ` Joe Jin
2018-10-26 14:40 ` Joe Jin
2018-10-30 2:51 ` Joe Jin
[not found] ` <57e5593233c64dc0a36c7d4c750a1ed4@AMSPEX02CL03.citrite.net>
2018-10-30 14:12 ` [Xen-devel] " Joe Jin
[not found] ` <097f1f6f16f7415aa3a52a7c4f5e52dc@AMSPEX02CL03.citrite.net>
2018-10-30 14:48 ` Joe Jin
2018-10-24 16:05 ` Joe Jin
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