From: Stanislaw Gruszka <sgruszka@redhat.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>,
Rosen Penev <rosenp@gmail.com>,
linux-wireless <linux-wireless@vger.kernel.org>,
Samuel Sieb <samuel@sieb.net>,
Alexander Duyck <alexander.h.duyck@linux.intel.com>,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: MT76x2U crashes XHCI driver on AMD Ryzen system
Date: Tue, 26 Feb 2019 11:34:51 +0100 [thread overview]
Message-ID: <20190226103450.GA2989@redhat.com> (raw)
In-Reply-To: <20190226100535.GA20740@8bytes.org>
On Tue, Feb 26, 2019 at 11:05:36AM +0100, Joerg Roedel wrote:
> On Mon, Feb 18, 2019 at 03:37:48PM +0100, Stanislaw Gruszka wrote:
> > 0001-mt76x02u-use-usb_bulk_msg-to-upload-firmware.patch
> > 0002-mt76usb-do-not-use-compound-head-page-for-SG-I-O.patch
> >
> > Or problem can be solved by just one of it (either first or second).
> >
> > Additionally I'm not 100% sure if
> >
> > 0002-mt76usb-do-not-use-compound-head-page-for-SG-I-O.patch
> >
> > is correct. So perhaps some IOMMU maintainer could look at it.
>
> The patch looks good, but I don't understand why it is needed. The AMD
> IOMMU driver should handle sg->offset > PAGE_SIZE just fine. Can you
> verify that this is the problem? I will look into that again if it turns
> out there is bug in the IOMMU driver.
I'm try to get that information from bug reporter, but I can't get it so
far.
If sg->offset > PAGE_SIZE is fine then most likely we have problem with
alignment. We use page_frag_alloc() in mt76usb for buffer allocation
in scheme like this
page_frag_alloc(max_payload); // something like 14434
page_frag_alloc(1024);
page_frag_alloc(2048)
page_frag_alloc(2048)
page_frag_alloc(2048)
...
page_frag_alloc works smart and fast way internally by allocating
fragments just but changing internal offset:
offset = nc->offset - fragsz;
if (unlikely(offset < 0)) {
page = virt_to_page(nc->va);
.
.
.
}
nc->offset = offset;
return nc->va + offset;
but unlike other allocators like kmalloc that make effort to provide
ARCH_DMA_MINALIGN buffers, it does not care about alignment. Above
scheme of allocation in mt76usb breaks it.
Note hat issue is with dma_map_sg(), switching to dma_map_single()
by using urb->transfer_buffer instead of urb->sg make things work
on AMD IOMMU.
Stanislaw
next prev parent reply other threads:[~2019-02-26 10:34 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
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[not found] ` <83A1D243-9073-48D1-9F26-5A2581DCB829@gmail.com>
[not found] ` <CAJ0CqmUgPWNJtCW4Q__sOtB8w-YtwW+uZy7crxMNrmSgQ6OFyA@mail.gmail.com>
[not found] ` <1547404075.1582.0@smtp.gmail.com>
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[not found] ` <CAKxU2N-+CTaRdJMFVRdozJ5TTpN+_4thiDRBJBFq8gGtuRVYvA@mail.gmail.com>
[not found] ` <20190114091841.GA23045@localhost.localdomain>
[not found] ` <CAKxU2N8ioMszBCyQcH7CVhgBdW4aj7yZ+kYQe14DCV5OSAnxrg@mail.gmail.com>
[not found] ` <20190115090400.GA2267@localhost.localdomain>
2019-02-18 14:37 ` MT76x2U crashes XHCI driver on AMD Ryzen system Stanislaw Gruszka
2019-02-18 15:15 ` Lorenzo Bianconi
2019-02-18 17:01 ` Robin Murphy
2019-02-19 11:08 ` Stanislaw Gruszka
2019-02-26 10:05 ` Joerg Roedel
2019-02-26 10:34 ` Stanislaw Gruszka [this message]
2019-02-26 10:44 ` Joerg Roedel
2019-02-26 11:24 ` Stanislaw Gruszka
2019-02-28 9:04 ` Stanislaw Gruszka
2019-02-28 10:42 ` Stanislaw Gruszka
2019-02-28 12:19 ` Stanislaw Gruszka
2019-02-28 13:40 ` Joerg Roedel
2019-03-04 7:10 ` Stanislaw Gruszka
2019-03-04 7:20 ` Rosen Penev
2019-03-11 8:43 ` Stanislaw Gruszka
2019-03-11 9:03 ` [PATCH] iommu/amd: fix sg->dma_address for sg->offset bigger than PAGE_SIZE Stanislaw Gruszka
2019-03-11 15:47 ` Alexander Duyck
2019-03-12 7:08 ` Stanislaw Gruszka
2019-03-12 15:18 ` Alexander Duyck
2019-03-13 9:03 ` [PATCH v2] " Stanislaw Gruszka
2019-03-18 10:17 ` Joerg Roedel
2019-03-12 7:13 ` MT76x2U crashes XHCI driver on AMD Ryzen system Stanislaw Gruszka
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