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From: Bjorn Helgaas <helgaas@kernel.org>
To: ranshalit@gmail.com
Cc: bjorn@helgaas.com, linux-pci@vger.kernel.org
Subject: Re: [Bug 205701] New: Can't access RAM from PCIe
Date: Fri, 29 Nov 2019 08:58:49 -0600	[thread overview]
Message-ID: <20191129145849.GA203450@google.com> (raw)
In-Reply-To: <bug-205701-41252@https.bugzilla.kernel.org/>

On Fri, Nov 29, 2019 at 06:59:48AM +0000, bugzilla-daemon@bugzilla.kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=205701
> ...
> 
> Using Intel Xeon computer with linux kernel 4.18.0 centos8.
> Trying to access RAM (with DMA) using FPGA  fails in this computer.
> 
> 1. I tried to add intel_iommu=off - it did not help.
> 
> 2. Installing windows on same PC - FPGA can access RAM using DMA without
> issues.
> 
> 3. using another PC (Intel Duo) with same linux and OS - FPGA access works.  
> 
> FPGA access the RAM using a physical address provided by a kernel module which
> allocates physical continuous memory in PC. (the module works perfectly with
> Intel Duo on exactly same OS and kernel).

Hi, thanks for the report!  Can you please attach the complete dmesg
and "sudo lspci -vv" output for the working and non-working v4.18
kernels to the bugzilla?

Then please try to reproduce the problem on the current v5.4 kernel
and attach the v5.4 dmesg log.  If v5.4 fails, we'll have to debug it.
If v5.4 works, figure out what fixed it (by comparing dmesg logs or by
bisection) and backport it to v4.18.

Bjorn

       reply	other threads:[~2019-11-29 14:58 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <bug-205701-41252@https.bugzilla.kernel.org/>
2019-11-29 14:58 ` Bjorn Helgaas [this message]
     [not found] <CAJ2oMhJ10FTcNH5wqWT2nfNz4jwG0BYr1DcVYTUPOcsSwpkMYg@mail.gmail.com>
2019-11-29 18:38 ` [Bug 205701] New: Can't access RAM from PCIe Bjorn Helgaas
2019-11-29 21:43   ` Ranran
2019-12-06  6:09   ` Ranran
2019-12-06 15:08     ` Bjorn Helgaas
2019-12-06 16:48       ` Ranran
2019-12-06 16:52         ` Ranran
2019-12-06 17:57         ` Bjorn Helgaas
2019-12-15 17:29           ` Ranran
2019-12-17 23:29             ` Bjorn Helgaas

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