From: Julien Grall <firstname.lastname@example.org>
To: Roman Skakun <Roman_Skakun@epam.com>,
Cc: Bertrand Marquis <email@example.com>,
Andrii Anisov <Andrii_Anisov@epam.com>,
Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>,
Oleksandr Tyshchenko <Oleksandr_Tyshchenko@epam.com>,
Oleksandr Andrushchenko <Oleksandr_Andrushchenko@epam.com>,
Roman Skakun <firstname.lastname@example.org>,
Jan Beulich <email@example.com>
Subject: Re: Disable swiotlb for Dom0
Date: Fri, 13 Aug 2021 11:51:47 +0100 [thread overview]
Message-ID: <firstname.lastname@example.org> (raw)
On 13/08/2021 10:38, Roman Skakun wrote:
> Hi Julien,
>> So 0xb6000000 is most likely the GFN used to mapped the grant from the domU.
>> swiotlb-xen on Arm will convert it to the MFN because it is not aware
>> whether the device is behind an IOMMU.
> If I'm understand right, it seems like that swiotlb-xen is not ready to
> work properly in case
> when we retrieved MFN instead of proper GFN mapped to Dom0 memory.
> Maybe you know some ideas to overcome this condition?
swiotlb-xen work as intended. You have a DMA buffer at an address that
your device cannot deal with. So it will try to bounce it.
>> As the address is too high to be handled by the device, swiotlb will try
>> to bounce it. I think it is correct to bounce the page but I am not sure
>> why it can't. What the size of the DMA transaction?
> The DMA map size is 3686400 bytes.
So that's a 3MB buffer. I am slightly confused because in an earlier
message you wrote that the memory is coming from the guest. How did you
> I've added several logs to swiotlb map_single() and see:
> [ 151.298455] <SWIOTLB> swiotlb_tbl_map_single() origin_addr:
> 64af97000, needed: 708,
> avail: 7fc0, stride: 2, index: 4160
I am not sure how to read the logs... Are the number in hexadecimal or
decimal? It might be useful if you post the diff of your changes.
> Swiotlb did not fit requested slots because the maximum slot size equals
> IO_TLB_SEGSIZE=128 by default.
Ok. So it sounds like your problem is the have a DMA buffer that is too
large for the default swiotlb. Did you try to bump the value from the
> But I think, we cannot use64af97000 address in the swiotlb_bounce()
I am not sure to understand what you mean. Can you clarify?
next prev parent reply other threads:[~2021-08-13 10:52 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-10 15:38 Disable swiotlb for Dom0 Roman Skakun
2021-08-10 16:16 ` 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 [this message]
2021-08-13 15:59 ` Roman Skakun
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