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From: Roman Skakun <Roman_Skakun@epam.com>
To: "sstabellini@kernel.org" <sstabellini@kernel.org>
Cc: Bertrand Marquis <bertrand.marquis@arm.com>,
	Andrii Anisov <Andrii_Anisov@epam.com>,
	Julien Grall <julien@xen.org>,
	Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>,
	Oleksandr Tyshchenko <Oleksandr_Tyshchenko@epam.com>,
	Oleksandr Andrushchenko <Oleksandr_Andrushchenko@epam.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	Roman Skakun <Roman_Skakun@epam.com>,
	Roman Skakun <rm.skakun@gmail.com>,
	Jan Beulich <jbeulich@suse.com>
Subject: Disable swiotlb for Dom0
Date: Tue, 10 Aug 2021 15:38:42 +0000	[thread overview]
Message-ID: <AM7PR03MB6593B4461B99297C8650CF1C85F79@AM7PR03MB6593.eurprd03.prod.outlook.com> (raw)

Hi, Stefano!

I have observed your patch here:
https://patchwork.kernel.org/project/xen-devel/patch/alpine.DEB.2.21.2102161333090.3234@sstabellini-ThinkPad-T480s/

And I collided with the same issue, when Dom0 device trying to use
swiotlb fops for devices which are controlled by IOMMU.

Prerequisites:
https://github.com/xen-project/xen/tree/stable-4.15
https://github.com/torvalds/linux/tree/v5.10

Issue caused in xen_swiotlb_map_page():
```
 dev: rcar-fcp, cap: 0, dma_mask: ffffffff, page: fffffe00180c7400, page_to_phys: 64b1d0000, 
xen_phys_to_dma(phys): 64b1d0000
```

There is retrieved MFN(0x64b1d0000), which belongs to DomU. Dom0
swiotlb couldn't proceed to this address and throws the log:

```
[   99.504990] rcar-fcp fea2f000.fcp: swiotlb buffer is full (sz: 3686400 bytes), total 32768 (slots), used 64 (slots)
```

Temporary, I resolved this issue by disabling swiotlb for dom0 at all
because sure that all devices goes through IOMMU, but this mention can
be true only for me.

But, I think of a more reliable way is to declare a special IOMMU
property in xen dts for each device. If the device controlled by IOMMU
not need to set swiotlb fops in arch_setup_dma_ops.
What do you think about it?

             reply	other threads:[~2021-08-10 15:39 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-10 15:38 Roman Skakun [this message]
2021-08-10 16:16 ` Disable swiotlb for Dom0 Julien Grall
2021-08-11  8:49   ` Roman Skakun
2021-08-11 10:30     ` Julien Grall
2021-08-11 14:13       ` Roman Skakun
2021-08-11 15:20         ` Julien Grall
2021-08-13  9:38           ` Roman Skakun
2021-08-13 10:51             ` Julien Grall
2021-08-13 15:59               ` Roman Skakun

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