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Date:   Wed, 5 Feb 2020 23:32:21 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Jian-Hong Pan <jian-hong@endlessm.com>
Cc:     Lu Baolu <baolu.lu@linux.intel.com>,
        Linux Upstreaming Team <linux@endlessm.com>,
        David Woodhouse <dwmw2@infradead.org>,
        iommu@lists.linux-foundation.org,
        Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] iommu/intel-iommu: set as DUMMY_DEVICE_DOMAIN_INFO if no
 IOMMU
Message-ID: <20200206073221.GA27797@infradead.org>
References: <20200203091009.196658-1-jian-hong@endlessm.com>
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 <948da337-128f-22ae-7b2e-730b4b8da446@linux.intel.com>
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On Thu, Feb 06, 2020 at 03:25:48PM +0800, Jian-Hong Pan wrote:
> Here is the original issue: There are more and more laptops equipped
> with Intel Rapid Storage Technology (RST) feature.  That makes the
> NVMe SSD hidden and as the cache.  However, there is no built in
> driver for it.  So, Daniel prepares a driver called intel-nvme-remap
> [1] to remap and show up the hidden NVMe SSD and make it as a normal
> SSD.  The driver is developed and refers to
> drivers/pci/controller/vmd.c.
> 
> Recently, we get a laptop with Intel RST feature enabled in BIOS and
> two NVMe SSDs after the RAID bus controller.  So, those two NVMe SSDs
> are hidden by Intel RST.  Then, intel-nvme-remap is going to remap and
> show up the NVMe SSDs.  But it hits two issues:

So you are using a driver that has been rejeced because it and the
Intel magic it tries to work around are completely broken, and then
complain it doesn't work?  There is no reason to hack up the intel-iommu
to work around your broken patched kernel then.