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From: Christoph Hellwig <hch@infradead.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	Anshuman Khandual <khandual@linux.vnet.ibm.com>,
	virtualization@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	aik@ozlabs.ru, robh@kernel.org, joe@perches.com,
	elfring@users.sourceforge.net, david@gibson.dropbear.id.au,
	jasowang@redhat.com, mpe@ellerman.id.au, hch@infradead.org,
	luto@kernel.org
Subject: Re: [RFC V2] virtio: Add platform specific DMA API translation for virito devices
Date: Tue, 29 May 2018 07:03:19 -0700	[thread overview]
Message-ID: <20180529140319.GA19972@infradead.org> (raw)
In-Reply-To: <2f1d48cf029c1f0903f3cffea946ae5b85f60ec0.camel@kernel.crashing.org>

On Tue, May 29, 2018 at 09:56:24AM +1000, Benjamin Herrenschmidt wrote:
> I don't think forcing the addition of an emulated iommu in the middle
> just to work around the fact that virtio "cheats" and doesn't use the
> dma API unless there is one, is the right "fix".

Agreed.

> The right long term fix is to always use the DMA API, reducing code
> path etc... and just have a single point where virtio can "chose"
> alternate DMA ops (via an arch hook to deal with our case).

Also agreed.

When Andi added vring_use_dma_api it was marked as temporary.

So I'd much rather move to blacklisting platforms that needs this
hack now than adding another exception.

And then once we have the blacklist move it to a quirk in the arch
code that just forces dma_direct_ops as the per-device dma ops.

I don't really think this is crazy long term, but something we could
do relatively quickly.  Interestingly enough the original commit
mentions PPC64 as a case where this quirk is needed.

  parent reply	other threads:[~2018-05-29 14:03 UTC|newest]

Thread overview: 80+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-22  6:33 [RFC V2] virtio: Add platform specific DMA API translation for virito devices Anshuman Khandual
2018-05-23 18:50 ` Michael S. Tsirkin
2018-05-23 18:50 ` Michael S. Tsirkin
2018-05-23 22:27   ` Benjamin Herrenschmidt
2018-05-23 22:27     ` Benjamin Herrenschmidt
2018-05-24  7:17     ` Christoph Hellwig
2018-05-24  7:17     ` Christoph Hellwig
2018-05-25 17:45     ` Michael S. Tsirkin
2018-05-28 23:48       ` Benjamin Herrenschmidt
2018-05-28 23:48         ` Benjamin Herrenschmidt
2018-05-28 23:56         ` Benjamin Herrenschmidt
2018-05-28 23:56           ` Benjamin Herrenschmidt
2018-05-29 14:03           ` Christoph Hellwig
2018-05-29 14:03           ` Christoph Hellwig [this message]
2018-05-29 22:13             ` Benjamin Herrenschmidt
2018-05-29 22:13               ` Benjamin Herrenschmidt
2018-05-25 17:45     ` Michael S. Tsirkin
2018-06-04  8:57     ` David Gibson
2018-06-04  8:57     ` David Gibson
2018-06-04  9:48       ` Benjamin Herrenschmidt
2018-06-04  9:48         ` Benjamin Herrenschmidt
2018-06-04 12:50         ` Michael S. Tsirkin
2018-06-04 12:50         ` Michael S. Tsirkin
2018-06-05  1:52         ` David Gibson
2018-06-05  1:52         ` David Gibson
2018-06-04 12:43     ` Michael S. Tsirkin
2018-06-04 12:55       ` Christoph Hellwig
2018-06-04 13:14         ` Benjamin Herrenschmidt
2018-06-04 13:14           ` Benjamin Herrenschmidt
2018-06-04 16:34           ` Michael S. Tsirkin
2018-06-04 16:34           ` Michael S. Tsirkin
2018-06-04 12:55       ` Christoph Hellwig
2018-06-04 13:11       ` Benjamin Herrenschmidt
2018-06-04 13:11         ` Benjamin Herrenschmidt
2018-06-04 16:21         ` Michael S. Tsirkin
2018-06-04 23:26           ` Benjamin Herrenschmidt
2018-06-04 23:26             ` Benjamin Herrenschmidt
2018-06-05  1:25             ` Michael S. Tsirkin
2018-06-05  1:25             ` Michael S. Tsirkin
2018-06-05  4:52             ` Christoph Hellwig
2018-06-05  4:52             ` Christoph Hellwig
2018-06-04 16:21         ` Michael S. Tsirkin
2018-06-04 12:43     ` Michael S. Tsirkin
2018-05-24  7:21   ` Ram Pai
2018-05-31  3:39     ` Anshuman Khandual
2018-05-31 17:43       ` Michael S. Tsirkin
2018-05-31 17:43       ` Michael S. Tsirkin
2018-06-07  5:23         ` Christoph Hellwig
2018-06-07 16:28           ` Michael S. Tsirkin
2018-06-08  6:36             ` Christoph Hellwig
2018-06-08  6:36             ` Christoph Hellwig
2018-06-13 13:49               ` Michael S. Tsirkin
2018-06-13 13:49                 ` Michael S. Tsirkin
2018-06-11  2:39             ` Ram Pai
2018-06-11  3:28               ` Michael S. Tsirkin
2018-06-11  3:28                 ` Michael S. Tsirkin
2018-06-11  3:34                 ` Benjamin Herrenschmidt
2018-06-11  3:34                   ` Benjamin Herrenschmidt
2018-06-13 14:23                   ` Michael S. Tsirkin
2018-06-13 14:23                   ` Michael S. Tsirkin
2018-06-11  3:29               ` Benjamin Herrenschmidt
2018-06-11  3:29                 ` Benjamin Herrenschmidt
2018-06-13  7:41                 ` Christoph Hellwig
2018-06-13  7:41                   ` Christoph Hellwig
2018-06-13 12:25                   ` Benjamin Herrenschmidt
2018-06-13 12:25                     ` Benjamin Herrenschmidt
2018-06-13 13:11                     ` Benjamin Herrenschmidt
2018-06-13 13:11                       ` Benjamin Herrenschmidt
2018-06-15  9:16                       ` Christoph Hellwig
2018-06-15  9:16                         ` Christoph Hellwig
2018-06-16  1:07                         ` Benjamin Herrenschmidt
2018-06-16  1:07                           ` Benjamin Herrenschmidt
2018-06-13 13:59                   ` Michael S. Tsirkin
2018-06-13 13:59                     ` Michael S. Tsirkin
2018-06-13 14:03                 ` Michael S. Tsirkin
2018-06-13 14:03                   ` Michael S. Tsirkin
2018-06-07 16:28           ` Michael S. Tsirkin
2018-06-07  5:23         ` Christoph Hellwig
2018-05-31  3:39     ` Anshuman Khandual
  -- strict thread matches above, loose matches on Subject: below --
2018-05-22  6:33 Anshuman Khandual

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